 Ok. Ok. Ok. We can start. Please take your seat. Welcome everybody for the inaugural ceremony of the Institute for the Fundamental Physics of the Universe. I'm Stefano Ruffo, the director of CISA together with ICTP, which is here represented by the director Fernando Quevedo and INFN with the director Fernando Ferroni and the National Institute of Astrophysics represented here by the director Nicolò D'Amico. We decided to create an institute which will use the facilities of the campus of CISA in Miramare which is only partially occupied right now and there will be two new floors that will open just in front of the main hall on top of the parking lot and that will be used by the institute. The two floors are already being cleaned and we are putting some furniture in place thanks to funding of ICTP because I discovered that CISA can spend very little money funding in furniture so we decided to agree that ICTP would make the most in this. Of course, yesterday, sorry, a few days ago there was the first meeting of the council that will direct the activity of the institute and Piero Ulio, who is sitting on the first row was proposed as the director of the institute and I will name him in the next days it's a very recent meeting so Piero will be the director of the institute CISA researcher and you will see him around everybody knows him perhaps so the activities as you have heard will be sort of constant running activities so the idea is not that of having big workshops or having too long programs but rather to have low intensity but deep activities in specific areas with research groups, presence of researchers so that is the idea of the institute so perhaps then Stefano Liberati will say more about this so I stop here because we are already late and I give the floor to the president of INAF Niholo Damiho, who can say a few words Thank you very much Of course, we are very happy that our institute is involved in this new venture and I really thank the organizers for asking INAF to join that in the universe there are things that we can see and there are things that we cannot see and things that we can see in the electromagnetic spectrum through the radiation but there is also dark matter, there is dark energy it is amazing that we do infer the existence of dark matter the existence of dark energy through observations of the electromagnetic spectrum of other sources in the universe it is clear that these two aspects observations of the universe through the electromagnetic spectrum and observation of the universe through other messenger that can send signal to us it is today very important and well, today we know that other messages arrives gravitational waves and they arrive from dark matter and we saw last year the amount of knowledge that we can get from a couple of observations in the electromagnetic spectrum and in the gravitational waves and so on so I think that the collaboration of this institution in this field can really produce a strong knowledge of the universe we have here in Trieste one of our research structure which is the astrophysical observatory of Trieste which is particularly devoted into cosmology so it is sort of a field which is very challenging today so I trust that this venture will really produce an outstanding knowledge of the universe Thank you very much Thanks a lot Niky and I now led the floor to the president of INFN Thank you very much I think it's an important day it is clear as Niky said that the new frontier in the research is the understanding of the dark universe and while until yesterday we were used to have instruments just to look at the bright side of the universe but now thanks to the observational waves thanks to the fact that high energy neutrinos are detected in our experiments placed all over the world I think there is a new opportunity and a new way to unveil what is this mysterious dark site it's an important event because it is, how to say, put together different institutes with different expertise with a way of working which might differ but all final goal is to understand nature better so I think that two important public research institute like ENAF and INFN and to an international centre of research and education like ICTP and this university which is a key in the system because it uses in the most noble sense people from the other different institutes that are possibly teachers and researchers in SISA so I think this is not an experiment this is actually an important way of conducting and indicating how to conduct research in the future I hope that this centre will express its potential very soon and allow us to make step forward and what is our final goal Thanks I give the floor to Fernando Javello the director of ICTP Thank you Stefano Welcome to everybody today is a landmark event I think this is very important for ICTP for the whole Trieste community to have this new institute I think in the Trieste we are very fortunate to have scientists working in different institutions covering different areas of cosmology and astrophysics and astronomy and having an institute like this will make our community far stronger and more influential in the region and also worldwide so I'm very pleased to see that we will have now closer collaboration with the observatory with CSAN and other institutions and having here the director of NFN and NF together with us this also shows how important it is for the nationwide institutions ICTP, I think we can play a key role in this institute because for several reasons one is that we can open it up for a larger community worldwide for the community from the developing countries which is our main mission and so in that sense we can bring more people from that community to these fields and also it expands our reach because there are some specialties that our colleagues have in the different institutions that we do not have so in that sense having a center this institute here will allow us to bring more scientists from different countries to participate in activities that we ourselves don't cover at ICTP so in that sense it will enrich our mission so I think we are very pleased to be part of this new initiative and I hope it will be a success I'm pretty sure it will be a success and then it's a perfect use of the facility that CSAN has and then we can share it all together and I hope that this is just the beginning of a great collaboration Thank you very much Thanks a lot to Niki Fernando and Fernando Rivera the last speaker of this first part so we will now proceed to the signature of the protocol of agreement so I will pass the copies for the signature and let's go in front for the picture Thank you Thank you So now Professor Stefano Liberati will make a brief presentation of the institute and also will present the inaugural talk by Professor Thank you Well, it's a pleasure to be here after a long journey to arrive to this point it is something remarkable I would say that so many scientists work together to create something new something that we strongly believe can be something important for the local community and we hope also for the international community as well In presenting the institute is not a refrain from starting with something which is a bit dramatic but I think is true I mean the universe was the start of everything and the universe was the start of science it was staring at the start in Bewillberment that led us to investigate nature and it is amazing how much from that first observation came out how much physics made the branch in many subjects from condensed matter physics statistical physics and particle physics and so on we basically specialized in many fields however not too long ago this was looking like an unstoppable tendency that everything has to become more and more limited and focused and in the last years there has been a growing understanding that the challenges that fundamental physics is posing nowadays are challenges that find their arena in the universe in cosmology, in astrophysics the biggest scales on earth the biggest scales in the universe are giving us answers to questions where the infinitesimally small and of course there has been in the last few years a wealth of knowledge that we have new discoveries like the exposure, the gravitational waves the high precision observations in cosmology, at the highest rate shift and the lowest rate shift with the large scale structure of the universe and so much more is coming and we felt that the challenges like dark energy dark matter are really telling us that it's the moment to come back to put together communities that haven't been working together for a long time both in theory and in experiments experiments nowadays in cosmology in astrophysics very often require fundamental physics to be interpreted and fundamental physics nowadays is posing challenges that requires the energies and the scales that are magnificence of the universe of cosmic physics and from this point of view we felt that Trieste was a special place Trieste is a special place in many ways even as a town is a special place but it's a special place scientifically because here there is a core a community that is spread over many institutions which is working on these teams and is an excellence community there isn't just a very good diversity within Trieste but in the region we have these four institutions that are united here nowadays in this today which are a point of excellence at the worldwide level and we started to be more and more felt especially in this industry set by people like Gigi Danez and so on that they were aware that there was a need to put this expertise together for the new challenges so we were strongly encouraged the new wave of people that was trying to develop these fields to stay together and so we found and I think this is something really remarkable a very strong feedback from our colleagues in the observatory in INFN and ACTP so I think that this is an example and I want to remark this of a case in which in Italy you are able to do what we call fare sistema that means to put together public institution that are separated to work together for the common good and this is something that very often in Italy we are not able to do but fortunately this was not the case and I think we were really helped by the vision of the people directing the four institutions that joined here and I think we all have to thanks their vision and also the people that contributed to create this institute so what about the mission of the institute the institute will be mainly dealing with astro particle physics astrophysical probes of fundamental interaction the early universe gravitational wave astrophysics theory and phenomenology of gravity these are the main fields in which we want to work and I think that we will start under the direction of Piero and with the contribution of our colleagues in the steering committee by putting together the local community so this is just one part as I say but they putting together the local communities to create a core, a critical mass to project toward the exterior at the international level we are very ambitious that will be a point of reference in the international landscape we don't want to just work at the local level and in this sense we think that this institution can be very important to put Trieste on the map as a town of science even more and this makes very clear that in our horizon there is a milestone which is as of 2020 that we want to be part of and I think that having touched all the speciality of Trieste and the special moment also in physics and astrophysics and cosmology it comes very natural to introduce today's speaker which is Giorgio Elles Giorgio in a certain sense is a living witness of the legacy that it makes Trieste special Giorgio came here called basically by Dennis Shama which happened to be a supervisor accidentally so was also mine and basically it is part of that history that makes Trieste so special and I think it's not by chance that several people that was linked to Giorgio is in the audience some of them are even in the steering committee so they contributed heavily in starting up this initiative the connection was very strong Giorgio was for seven years professor of cosmology in CISA and he contributed very much to the legacy that we built upon Giorgio Elles is a fellow of the Royal Society he did his PhD in applied mathematics and theoretical physics at Cambridge University as I said with Dennis Shama he quoted the large case structure of space time with Stephen Hawking and he's now professor emeritus of applied mathematics at the University of Cape Town he's also visiting professor at the physics department of the Oxford University I want to say that he also has a role for something that we really care about here in Trieste which is third world countries and he's a member of the third world academy of science and he's recently also spread his range of interest well beyond well not well beyond physics but connecting physics with neuroscience recently wrote a book for example that is entitled how can physics underline the mind top down causation in the human context so it's really a pleasure for me to introduce Giorgio Elles and he's talked about remarkable interaction fundamental physics, astrophysics and cosmology, thank you well it's a great pleasure to be here at this occasion it's a great honour and I'm very happy to be able to take part in this inauguration so the goal of the institute is to promote projects and activities relating to investigating the fundamental laws of nature in connection to astrophysical and cosmological observations now I'm extremely conscious that there are many people here who know a lot more about much of this than I do on the other hand I'm also aware that given the wide nature of what is envisaged there's actually nobody who on their own knows everything about all of these topics and that's why the institute is needed it's to bring together the people who know the different parts and form a community that can together try and tackle these issues now local physics determines the evolution of the universe gravitation plus the equation of state of matter gives you the standard model of cosmology and of astrophysics gravitation in the standard model of particle physics allows stars, planets and biology to emerge from interacting particles so this is the issue of emergence of astronomical objects and then of complexity but the universe determines the outcomes of local physics things would have worked out differently if the universe were different and this is one of the things that Dennis Shijama used to emphasize and this is what enables us to test particle physics via astronomical observations we are able to exist because the universe together with local physics created hospitable environments of life so our existence is because of the nature of the universe so the universe is a vast scale it's expanding it started off in a hot big bang structures such as galaxy clusters formed by gravitation attraction and stars and planets formed in this environment and so typical galaxy is 100,000 million stars if we look out with our new telescopes we can see 100,000 million galaxies within the observable part of the universe and there is this incredible immense size of what we are seeing we can only see them because of these extraordinary telescopes you can't see this with the naked eye now the static cosmology of Einstein and De Sitter in 1917 were replaced after some initial resistance by the expanding universes of Friedman and Lemaître and I must emphasize at that time all of the eminent people in cosmology knew that the universe was static Einstein knew it Eddington knew it and so on and it came as a great surprise to cosmologists to discover that the universe was expanding it's one of these things which they didn't expect that's the hallmark of a scientific discovery so we have now a family of exact solutions of the general relativity equations Einstein field equations in the walker geometry which means on a large scale the universe is incredibly simple it's spatially homogeneous everywhere there's no preferred place and it's isotropic there's no preferred directions and that's an extraordinary simple structure on the very larger scale there's a scale factor A which we can think of as the size of the universe very important is the expansion rate H which is the logarithmic derivative and then important are the density and pressure, rho and p which are the matter parameters and I will use units in which the speed of light is 1 the major discovery was the dynamic models of the cosmos or possible and that was Friedman and the Matrix incidentally Newton tried to get models of the universe he couldn't do so because if you use a force law and try to construct models of the universe the force diverges and so Newton tried to do this and couldn't do it the static solutions are unstable so expansion or collapse is inevitable which was Eddington's discovery and these models these dynamical models of the universe unify falling apples the motion of the moon around the earth and the earth around the sun and the expansion of the cosmos because these are all determined by that one simple law of gravity which is now Einstein's theory and then these models are observation testable Hubble, I put in brackets because Hubble never actually believed in the expanding universe, why not? because his estimates of the Hubble constant was wrong by a couple of factors and therefore when Hubble died it was still the fact that if you used his estimate of the age of the universe it was younger than some of the older stars in the universe this has always been one of the great tests of cosmology and this is a relation between local astrophysics and cosmology are the ages of stars older than the age of the universe if so, you are in trouble ok, well we have revised the Hubble constant due to many new measurements and Lemaître, McVitty, Heckman sandwich and others instituted observational cosmology as a science but there are visual and causal horizons there is a limit on how far you can see this is one of the major things about cosmology Light has been travelling to us since the start of the universe 13.7 billion years ago that means you can't see anything which is essentially further out than that distance there was an initial singularity we believe that is indicated by classical gravity and that is something I will come back to at a later stage so, what we want to do in observational cosmology is to determine a set of parameters the Hubble constant today the rate of expansion today the matter density today the matter density today which we normalize we divide the matter density by 3 times the square of the Hubble parameter and this is then a dimensionless quantity it is always a good idea to have dimensionless quantities and the critical density is then when this density parameter omega is equal to 1 if the density is greater than 1 in essence the universe wants to collapse and if it is less than 1 in essence the universe wants to expand forever deceleration parameter today is the second rate of change of time of the expansion parameter that again is made dimensionless by dividing by 1 over h0 squared this q0 this is telling us if the expansion of the universe is speeding up or slowing down a fundamental feature there is the cosmological constant which Einstein introduced which we will talk about later and very important is the normalized spatial curvature because we are dealing with Einstein's theory of relativity the space sections of the universe can be flat or elliptic or hyperbolic if they are elliptic if you were to go out of that wall and keep going long enough you would re-enter through that wall if you were to go up that way go long enough you would re-enter through the floor so that would have closed spatial sections now at this very moment the universe is very very close to being flat this parameter the dimensionist parameter k over h0 squared is very very close to 1 but I must emphasize particularly for the observational cosmologists it is completely different claiming this is close to 0 from saying it is 0 to say it is 0 means that omega k is 0 to all decimal places if you were to find a non-zero term in the 250th or the 2000th term or the 10 millionth term it would not be flat so there is a crucial difference between being almost flat and being actually flat being actually flat requires infinite fine tuning and so I always try to emphasize to my observational colleagues please try and determine if the universe, if omega is positive or negative, is the spatial curvature flat or not it is far more interesting if it is positive than otherwise and I could talk more about that so the background model there are three equations the conservation equation the evolution of matter density gives you the rate of change with time of the density of matter, that's the first one and note that rho plus p there is the inertial mass density I'll come back to that and this is the basically energy conservation equation it says that the kinetic energy potential energy of the universe give you a constant or you can reinterpret them to say matter curve space and that is why the curvature term enters in that equation take the time derivative and you get what's called the rate chargery equation or the acceleration equation this gives you the rate of change of time of the scale factor and the crucial factor is that the act of gravitational mass is rho plus 3p it's the density plus 3 times the pressure this is completely different than Newtonian theory and this is important in terms of the singularity properties of the universe and all of its dynamics any two of those equations imply the third but they're not complete and what is crucial then is you need an equation of state of matter and the pressure in terms of the density in order that these equations become a deterministic system and this is how local physics changes the evolution of the universe so if you then put that equation of state into one you determine rho as a function of a put that into either of those two and you work out how the universe expands and so if you are a radiation dominated then the pressure is a third the density the scale factor goes as t to the half and the pressure decays is 1 over A and this is why the universe is cooling down now and it was hotter in the past this tells us there was a hot big bang in the past where nuclear synthesis took place, element abundances were fixed and then matter and radiation were tightly coupled to each other but then they decoupled leading to the existence of the cosmic microwave background and its spectrum and its anisotropies this was followed by the matter dominated era when the pressure was zero and then instead of t to the half you get t to the two thirds the Einstein decider universe and then at very late times it's become dominated by a cosmological constant and now it has an exponential expansion and so we go through phases the Tolman phase the Einstein decider phase through to the decider phase and we're in that last phase today and this is how micro physics changes the macro structure how do we know this is all correct well one of the crucial things is we've measured through the Kobe satellite with incredible accuracy the black body spectrum emitted by that hot radiation with a temperature of 2.73 degrees k together with primordial element abundances that's confirmed from us without any doubt that there was a hot big bang era and in terms of what this project is about it tells us that quantum mechanics was the same 13.7 billion years ago as it is today that's a very very fundamental statement about the nature of the universe because that black body spectrum as determined by Planck results from the nature of quantum physics so this is direct evidence that quantum physics was true in exactly the same way at that time in the past of the universe this is followed by nuclear physics processes during the hot big bang era an epoch of nuclear synthesis elements form in the early universe at a temperature of about 10 to the ninth degrees Kelvin and this is when nuclear physics tells us what happens, neutrons and protons combined to form deuterium, helium and lithium one of the things that was discovered from this way back was that this requires there be no more than three neutrino species and this is a discovery which came from the cosmology side and was only later confirmed by experiments so this is a triumph that this project is aiming at the heavy elements spread through space much later having formed in the interiors of stars and are spread by supernova explosions and that's the basis of the crucial elements of life on Earth all of the materials out of which this room is made and out of which we are made were formed not in the early universe but in these supernova and this is what the theory says if you change the density of ordinary matter very different kinds of densities the fractions of the different elements are given vertically helium 4 at the top, deuterium next, helium 3 at the bottom next and lithium there and if you consider different variations of this density this is the one value where all of these experiments agree with each other and so this tells us the density of ordinary matter that is the density of baryons relative to the photons so if all four observations agree if the baryon density is about 0.02 up to some worries about lithium now a key discovery then is the rotation curves of galaxies and motions of galaxies and clusters indicate the presence of dark matter that is matter which is unseen because it doesn't radiate but it's felt through its gravitational field the density of dark matter varies with scale but cosmologically contributes about 0.3 and this is much more than that density of baryons which we felt saw in the last slide the presence of dark matter is confirmed by gravitational lensing so dark matter is required because if you take galaxy rotation curves you've got your measured curve as shown as the top but visible matter can only account for a rotation curve like that so the rotation of the galaxy and so you need dark matter to make up the difference and so this is the initial evidence for dark matter also we need it from cluster dynamics and structural formation so nuclear synthesis theory and element abundances agree providing the baryon density in universe is low about 0.02 and these dimensionless units the dark matter from astrophysical and cosmology plus gravitational lensing which also helps give us 0.3 together they provide evidence for much more non baryonic dark matter than baryonic matter this huge surprise and so for particle physicists and for cosmologists what is the nature of this matter the existence of non baryonic particle is a key issue for physics today we can test for this in many ways possibility shows massive compact halo objects which could be black holes faint stars or planets but gravitational lensing rules most of these are it could be axions in a specific mass range providing solution to the strong cv problem but they haven't been detected it could be wimps weakly interacting massive particles which can be in principle directly detected by particle detectors they can be produced in particle accelerators and they can be observed by their decay products and could it be a neutrino the supersymmetric part a partner of the neutrino we can search for its gamma ray and neutrino decay products or we can try direct detection for instance through cryogenic dark matter search and so this is one of the major topics which this institute will be looking at but we could also think maybe we're getting the dark matter because we're using the wrong theory of gravity the deduction depends on deducing what the rotation curve ought to be on the basis of the baryons if that theory of gravity is wrong maybe there's a modified Newtonian gravity or similar then we would be going down the wrong street looking for these particles so part of this is to look very very carefully at all the astronomical evidence is Newtonian gravity right on these scales as general relativity right on these scales we need modified gravity to apply for this typical kind of observation which relates to this is the anita anomalous detection asignets as beyond the standard model particle and supporting evidence from ice cube cosmic rays showers emerge from the earth which exit angles of 27 and 35 degrees while up going showers have been anticipated as a result of astrophysical tau neutrinos converting to tau leptons during earth passage these exit angles as long for that interpretation there is no particle that can propagate through the earth with probability greater than 10 to minus 6 at these energies and exit angles and in this paper they explore whether beyond the standard model particles are required to explain the anita events if correctly interpreted and conclude that they are so this is astronomical evidence that we need beyond the standard model physics huge discovery in terms of the background model evolves with the discovery that scalar fields which obey the Klein Gordon equation can give you an energy density like that, a pressure like that and the key point is here rho plus 3p for scalar fields is d phi by dt squared minus v of phi and can be negative it can be less than zero if slow rolling in other words if the kinetic term is very small then there is a negative number there gravitational mass becomes negative and so you have anti gravity and so the act of gravitational mass of scalar fields can be negative a very surprising discovery this can give you an exponential expansion for a very brief period before the hot big bang era which smooths out and flattens the universe goofs discovery of the inflationary cosmology idea so inflation it is claimed explains why the universe is smooth and flat but I put a lot of question marks there because it is maybe not true Roger Penrose has written very convincingly that this discovery only works if you ignore the entropy of black holes which could have been there and if you take gravitational entropy into account then inflation does not explain the smoothness and flatness of the universe on the contrary it requires in order that inflation can ever begin and this is a very interesting topic which I will revert to at the end if I have time but in any case the key point is what is the inflatona and we have no unique candidates in fact we have about 150 candidates for inflation candidate models inflation is not a specific theory it is a whole plethora of theories and one of the things which is not at the moment sorted out properly is what is the inflatona and that is another topic to be examined OK, perturbation solutions what one has to do is take these smooth models and perturb them and this gives us the theory of growth of structure James Jean started this off the made to try to look at it but the crucial paper that changed everything with lift shits in 1946 where he introduced scalar vector and tensor modes, Fourier analysis and one of the problems which plagues this gauge issues which have to be treated with great care I won't talk about that but these fluctuations caused cosmic background radiation and isotropies one of the great papers in cosmology is Saxon Wolf in 1967 the result of these structural formation calculation depends on the nature of the matter and radiation interactions so we've got inflation which generates almost scale free seeds by quantum processes we have baryon acoustic oscillations during the hot big bang era where gravity tries to compress the plasma the pressure resists it and there's this tight coupling between the electrons and protons which enables this to happen so you get oscillations that comes to an end when decoupling takes place due to baryons and the dark matter cause a structure to form and so we have a successful theory of structure formation one of the great triumphs of cosmology the results depend on the global parameters and in a dimensionless form the second derivative of the density perturbation has a term which depends on the expansion rate it depends on the Hubble parameter and a source term which is the matter density but the crucial point here is that the matter density there is a background quantity and so if you change the background model you get different results for structure formation so the global parameters determine the outcome of local evolution for instance in the static case theta is zero and that term goes away and in that case you get this equation and you get an exponential growth which is what genes found and so instead of getting the the power law which is what happens in the matter in radiation dominated here is you get exponential expansion and so this is the top down effect of the universe on structure growth now we've got massive new observational data, astronomy and cosmology means transformed by the vast new sets of data coming in enabled by new technology for instance charge couple of devices and so we are now receiving electromagnetic radiation right across the spectrum from satellites measuring neutrinos measuring gravitational waves and we've got statistical surveys of vast numbers of sources enabled by fiber optics and we've got the computers to handle the vast amounts of data coming in and so all of this put together gives us checks on structure formation theories in physics so we need all wavelengths in order to get above the regions above the absorption bands in the sky and so you can see there that the optical gets through and radio gets through but most other wavelengths don't get through which is why we need the satellites the key set of observations which one the Nobel Prize is the decay of supernova in distant galaxies provided a usable standard candles because the maximum brightness is correlated to the decay rate with redships that gave the first reliable detection of non-linearity that is that Q naught I talked about showing the universe is presently accelerating a huge surprise to cosmologists at that time consequently there is presently an effect of positive cosmological constant with parameter value 0.7 much bigger than dark matter and very, very much bigger than baryonic matter and its nature is unknown galaxy surveys huge numbers of galaxy surveyed with their redships strong gravitational lensing provides you with evidence though these multiple arcs of the same source provide you with evidence of distant matter which you can't see in any other way weak gravitational lensing enables you to detect the dark matter which is there which you can't see in any other way and the cosmic microwave background temperature fluctuations here measured with exquisite precision from the Planck and W map satellites show that anisotropy in one part in 100,000 the primordial fluctuations once you remove the dipole which is one part in a thousand so your perturbation data on the left there is the matter correlation functions across scales with a peak and the baryon acoustic oscillations is in there if you look carefully enough one is the famous acoustic oscillation seeing in the cosmic background radiation spectrum in one of the triumphs of this whole subject these peaks were predicted before they were observed and the fit between the theory and the observation is absolutely brilliant as you can see there you've got about 4 parameters you can tweak and given those parameters you get this brilliant consistency and what happens comes out of this is perturbations provide the best test for cosmological theories the supernova data is directly testing the the geometry as in sandages day by using standard candles to directly test the curvature of spacetime the clusters are indirectly telling you the curvature of spacetime because the spacetime curvature as I've just been emphasizing changes the structural formation properties of galaxies and the cosmic background radiation and isotropies tell you the background parameters because the background parameters determine the structure formation and the structure formation determines the anisotropy in the microwave background radiation and so testing model by standard candles a direct test versus the outcomes of structure formation the indirect test wind and give you the much clearer much greater precision so we've got our concordance model in expanding perturbed Robert Friedman the matrimodel it evolves from a hot big bang era when its nucleosynthesis took place preceded by inflation universe has nearly flat space sections as expected on the basis of inflationary theory the total matter density is the matter density of 0.3 which is dark matter plus the cosmological density of 0.7 adds up to about 1 both dark matter and dark energy and are important at late times but their nature is unknown the Hubble parameter 72 plus or minus 5 kilometers a second giving you an age of 13.8 time 10 to the 9 years there's a tension between distant and close measures of the Hubble parameter which needs resolution and that's one of the things one should look at in this institute and this is the famous standard expansion history from NASA illustrating all of that now one of the key issues what is the equation of state of the dark energy it may be a cosmological constant there's nothing there telling us at the present time it is not a cosmological constant but there's the issue of vacuum energy I'll come to in a minute it may be a dynamical field called contestants one of those scale of fields I mentioned briefly earlier in that case we need to know what is its equation of state that depends on its potential if it is a scale of field there is a phenomenological equation of state p is w rho now that tells you nothing about the physics it's just a curve fitting exercise so there is no real physics in that relation there is a possibility of what's called a chameleon field an environmentally dependent field which gives you a variable effect of s that's one possibly the one only way of trying to get a real physics explanation of what the dark energy is but we have a problem and the problem is the following the momentum equation is rho plus p it normalize units times the acceleration plus the gradient of the pressure is zero that tells you that the pressure gradient gives you an acceleration with the inertial mass density rho plus p which in these terms of parameter w is rho into one plus w that means we have a major problem if the astronomical observations tell us that we have quintessence a varying equation state with w less than minus one because then that term is negative that means then you would have matter which if you push it in that direction the matter goes in the opposite direction because it's got a negative inertial mass density that's a major catastrophe it means that the matter is highly unstable it's unlike any matter that you've ever accounted is highly unlikely and this could be telling us that maybe we need an alternative theory of gravity and that what's really wrong is we're using the wrong theory of gravity on these scales that could be one interpretation of what is going on the issue of vacuum energy is the problem of the vacuum energy is that quantum field theory vacuum energy suggests a cosmological constant which is huge much much bigger than the value we measure if you do simple quantum field theory calculations like Weinberg and others have done you get rho vacuum greater than 10 to the 70 which is a great tail greater than 0.7 now I'm emphasizing that this is a consequence if we take a simple view this should be curving the spacetime it should be causing the spacetime to expand incredibly much faster than it is doing I'm emphasizing we're putting together best-tested physics theories we have general relativity in quantum field theory and on a simple interpretation they are in dire conflict with each other and any full quantum theory gravity should have this as a limit so the issue is does the vacuum gravitate if so we have a major problem the vacuum energy disaster, the Ray-Chardry equation I showed you before shows that the rho plus 3p is the act of gravitational mass density if we include the vacuum energy density of the source term that equation is a disaster one way out of this is to use the trace-free Einstein equations as an alternative of the Einstein equations the vacuum does not gravitate if we use the trace-free Einstein equation plus separate conservation equation and this is another theory of gravity called unimodular gravity in that case the gravity doesn't gravitate the vacuum doesn't gravitate this solves a profound contradiction arising between quantum field theory and the Einstein equations if we join them in the obvious way and this is one of the indications that gravity may really be a conformal theory very, very briefly what you do the standard Einstein equations rab minus a half rgab plus lambda is zero and the energy conservation equation separately take the trace-free part and you get a minus a quarter instead of a half and that is the trace-free equations of which they are unine so in the trace-free gravity you assume those are the gravitational equations and you assume that those equations separately and in that case the vacuum energy has been disempowered and has no gravitational effect this solves the problem lambda appears as the integration constant as in standard general relativity and doesn't cause us the same disaster this is related to unimodular gravity which I think is a good way to go in terms of gravitational theories astrophysical black holes astrophysical black holes the solution was discovered in 1907 by Schwarzschild and Drosti it was interpreted as black holes only in 1960s it took a very, very long time for astrophysicists to understand general relativists to understand the black hole solution it was a mathematical curiosity but the question is do they occur are they relevant for astronomy and astrophysics and now we have a resounding yes, they are the in-state of gravitational collapse for stellar mass black holes which are surrounded by accretian discs there are massive black holes powering quasars, there are massive black holes of the center of gravity there are the sources of high energy radiation from accretian discs primordial black holes might be dark matter so I anticipate that astrophysical black holes will be a central feature gravitational wave detection gravitational waves in general relativity theory were predicted by Einstein in 1917 there was then a theoretical debate if they actually existed because of the nature of general relativity they could have just been a coordinate effect not real physical effects this was clarified in the 1970s by Triton, Pyrramonie, Bondi, Saks Newman and Penrose in which we changed from thinking about the metric tensor about vile tensor propagation and then it's absolutely clear that gravitational waves exist and then they were famously detected in 2016 using incredible technology giving a new window in the universe where we could detect black hole collisions neutron star collisions limits on the stochastic background here is the LIGO the LIGO and Virgo detectors are incredible detectors this is Virgo up near PISA unbelievable technology which I don't have time to go into but the detection sensitivity one part in 10 to the minus 22 absolutely unbelievable that's the Virgo sensitivity curves and here is the gravitational detection from two merging black holes at Hansford, Livingston and Virgo in which case you see the pattern that was detected the strain at the bottom and the next run up you see the frequency as a function of time and most importantly the gravitational detectors are by two neutron stars sparing together and merging and these signals are very very difficult to see there again you can see the pattern of the frequency changing with time because these were neutron stars rather than black holes enormous amount of other radiation was given because the neutron stars have got a very complex objects the associated electromagnetic signal was seen by 70 observatrix on seven continents and across the electromagnetic spectrum and that was the serious birth of multi-messenger astronomy in which we detected fast moving rapidly cooling cloud of neutron rich material and debris ejected from the neutron star merger and this to me is one of the most exciting things to come out of this this is a picture with time from left to right of the signals across all of the frequencies gravitational waves you probably find it difficult reading that the I was finding it difficult reading that gamma ray, x-ray ultraviolet optical, infrared and radio waves, all of those signals and one of the key things there is that there are time delays between it occurs at the different wavelengths and so you can see when the signals are received at different times at ways of detecting and that provides us with incredible detailed information about what it is so neutron star mergers give you multi-messenger astronomy where these signals are many kinds as we just saw on that last slide and that enables us into alia to test neutron star equation of state via the tidal distortion of the neutron stars which affects the gravitational wave spectrum and so we can test particle physics the behavior of standard model of particle physics in this neutron star context which you cannot replicate in a lab by measuring these signals and these are calculated different spectra for different equations of state and different neutron star masses as you go down those are different equations of state as you go across those are different neutron star masses and these can be compared with observations and can be used from these observations to give you limits on neutron star equations of state and therefore to work out how the standard model of particle physics works out in those extreme conditions so information from gravitational wave observation direct measure of the Hubble constant constraints on cosmic strings the merger rate of binary neutron stars detection of our process nucleosynthesis in colliding neutron stars which is a very interesting development relation to gamma ray bursts limit on the neutron star equation of state for instance cork meson coupling model can be tested limits on the masses of neutrinos tests of gravitational theories for instance the speed of gravitational waves do we in fact have massive gravitons rather than massless gravitons that we mostly believe in so Newtonian theory there are no gravitational waves general relativity there spin two gravitational waves traveling at the speed of light but what is very important in general relativity in a spherical gravitating system the system is independent of the ex theory this is Birkov's theorem which is a local result and Birkov's theorem is one of the most important results in general relativity it's not celebrated enough it tells you if you have a spherical star spherical star I'm emphasizing what happens outside doesn't affect it and so if you have a very spherical star which is pulsating it cannot emit gravitational waves if the correct theory of gravity there are no spherical gravitational waves so in oscillating spherical star does not lose energy by gravitational waves in more general theories such as scalar tensor theories or string theory which have a gr limit plus a dilaton it is perfectly possible there would be spherical gravitational waves these would have astrophysical effects and should be detectable so this could be a very interesting kind of thing to look at another constraint on fundamental physics and here I'm straying far from my field but nevertheless it seems to me to be very interesting there are string theory problems I understand if because observations show lambda is positive because there is this huge landscape of string vacua it's believed to lead to consistent effect of field theories which are conjected to be surrounded by a swamp land of inconsistent semi-classical effect of field theories which do not allow for inconsistent theory of quantum gravity observations show the universal present is close to the sitter but supersymmetry and these theories prefer anti-decider the word anti-decider occurs in almost all of these papers in other words a negative cosmological constant and so there is a question how can the positive cosmological constant be compatible with some of these implications of some interpretations of string theory and there is a major current debate going on in some people and this is from now much much more about this than I do it has been suggested that this might rule out many m-theory proposals because we do not live in an 8-year spacetime and there has been a Kantist claim saying that that's all wrong well this is the kind of thing which is cosmology is telling you lambda at the present time is positive that may have implication for fundamental physics in this way I want to return to Dennis Schjama and Herman Bondi who emphasized top down effects in cosmology in the synthesis the primary element abundance is the rate at which the elements are formed and the outcomes depend on the fact that you had that tolman solution at that time so cosmology determines those outcomes structural formation I've emphasized depends on top down effects all this paradox the fact that the night sky is dark which is necessary for life on earth follows again this is one of the ones which Schjama and Bondi used to talk about are understanding now that the night sky temperatures 2.75 degrees Kelvin Max Principle the origin inertia is one of the things which was debated at great length people don't talk about that anymore but the one which is important is the arrow of time we need very special initial conditions at the start of the universe to give a preferred direction of time out of time symmetric physics at the bottom and so the question is what were those very special initial conditions and how do they give you an arrow of time in local physics and to me this is still one of the important issue which needs looking at one of the things which has been looked at is the possible variation of fundamental constants for instance does the fine structure constant vary in the distance universe and there have been some observational tests suggesting that the fine structure constant is distant at very very far galaxies some people might say this is suggested by the string theory landscape so observation tests of such variation is a very interesting thing to engage in I want to emphasize one thing which to me is important the quantum measurement issue collapse of the wave function underlying all of these physics is quantum measurement how do we measurements take place and I believe it takes place by collapse of the wave function where this occurs in cosmology is two interesting cases how do quantum fluctuations become classical in inflation which is an unsolved problem how do nucleosynthesis results become classical again I don't say this is an unsolved problem but it's something that one should understand and plausibly this takes place by what I call contextual wave function collapse in which the wave function collapse process the measurement process leads to the passing of time and loss of information so one of the things which I would suggest doesn't need looking at is how does quantum gravity relate to the quantum measurement issue whatever your solution to the quantum measurement issue is I think this is something needs looking at and I must emphasize here the wave function has no meaning without the eigenvalues and states associated with collapse and so this may not be what you thought you were going to be looking at in this institute I believe this is what leads to the arrow of time in fact in the direction of time what you've got there is a direction of time which is from the start of the universe to the present day and you've got local arrows of time and local arrows of time there's a electro dynamic arrow of time there's a thermodynamic arrow of time there's a gravitational arrow of time associated with gravitational radiation there's a psychological arrow of time and so on there's a lot of local arrow of times and one of the very interesting things does the cosmological direction of time relate to these local arrows of time and this is one of the most important top down effects from the universe to local physics and indeed to fundamental physics and and here you have this issue you've got your quantum fluctuations which become classical fluctuations you cannot predict which specific galaxies will exist today because it is a quantum process in which the outcomes that take place cannot be predicted just as in the two slit experiment and so I think this issue of how the quantum fluctuations become classical is a very interesting one okay, the cosmology relation to physics you've got gravity, atomic physics nuclear physics, particle physics and quantum gravity gravitation we understand the universe expansion dynamics the Hubble diagram unifies the apple, the moon and the universe atomic physics, equilibrium and decoupling background radiation spectrum gives you this black body spectrum and cosmic background radiation nuclear physics nuclear synthesis gives you element abundances and nuclear reactors and nuclear synthesis all of these, the unification is fantastic, where it starts to fall apart this level here, particle physics the inflaton and the cosmic background anisotropies, we don't know what the inflaton was and my view is that the idea that the inflaton should be the Higgs field is one of the most interesting ideas to pursue in inflationary cosmology because if the Higgs is the inflaton, which is possible it is one of the ones which is consistent with the plank data then you have an incredible unification of particle physics and cosmology because the particle responsible for mass in nuclear is also the particle responsible for structural formation in the universe so I am a strong believer in the idea of Higgs inflation I think we should pursue it, it's the one case in which we obtain a satisfactory unification of particle physics and cosmology at the inflationary time quantum gravity we do not know what the quantum gravity theory is at the moment there are various competing quantum gravity theories and we don't know if they lead to a start to the universe or not, this is one of the great unknown areas so Higgs inflation is no real relation to physics except if the standard model Higgs boson is the inflaton and various people have looked at that if you want to add a basian prior to your study of cosmology this is it it requires a non-minimal coupling with a large coupling constant and so some people say you should discard it on those grounds but why should we expect natural coupling constants, this is something which has been debated it's a philosophical assumption and Sabine Hossenfelder has just written a book about this lost in math saying we should not take this idea of natural couplings as important as they have been done this is the kind of philosophical assumption which changes the way that we do some of our physics was there a start to the universe I'm not going to go into that in detail we don't know is the answer according to the classical theory there was a start to the universe if the energy equations were satisfied but we now know because of inflation they were not satisfied in the early universe and we do not know what quantum gravity says a string loop quantum gravity suggests there was not a beginning to the universe but in the end this is at the moment uncertain territory this is because of the physics horizon there are limits to what is testable in the laboratory in the solar system we have to extrapolate known physics to domains where they are untested and maybe untestable different extrapolations of known physics are possible with different outcomes for instance one extrapolation of known physics leads to string theory another leads to loop quantum gravity these are different extrapolations these uncertainties increases in the very early universe hence testability declines particularly in terms of theories of creation of the universe in which there have been many but we are extrapolating known physics in terms of theories of creation of the universe to theories where physics didn't even exist and this is a very difficult thing to try to handle one of the things I just want to return briefly to Penrose why is gravitational entropy so low at the start of the universe and inflation does not solve this the thermal entropy to the maximum gravitational entropy is very low which implies he says that the inflationary scenario is incredibly unlikely penrose resolution is what he calls conformal cyclic cosmology which is a very interesting one but I think it's got some problems but you probably know that he's recently claimed that the cosmic background radiation supports that model which is something of interest my own view is that one can go to a proposal that Brian Green many years ago this is solved if you have a gravity theory that turns gravity off in the very early universe and then turns it on at a later time and Brian Green wrote a very interesting paper on this and this is something which I think is a very interesting attempt to solve this problem of the homogenegative of the universe why it is so homogenous to allow inflation to start ok major questions what are the cosmological parameters and particularly is the spatial curvature positive or negative apart from that we know the parameters pretty well what do they tell us about inflation there's a huge amount of work going on about that is the universe open or closed how does structural formation take place what's the nature of dark matter what's the nature of dark energy one I haven't mentioned so far but it's very important what's the mechanism of baryon, anti-baryon asymmetry this is another very important one for the present day which does not have a resolution at the present time this is a great time to initiate IFPU there's much to be done I have one final comment for you remember you will be probing the boundaries of testable physics and cosmology I therefore urge you to take philosophy seriously because you cannot avoid it when dealing with these issues this is because you will be dealing with the boundaries of what is possible to test in laboratories and even in cosmology because of remember of those visual horizons so this issue of naturalness arises should your theories be limited to those that are natural or not, Hossenfeld has suggested they should not be limited in that way the issue of testability comes up in cosmology because of horizons and in quantum gravity the comment I would make here please avoid the use of the word infinity in physical models infinity does not in my opinion occur in physical reality as David Hilbert famously argued a long time ago infinity is not a very large number and many cosmologists nowadays talk about infinity as if it's a very large number it's not a very large number it's bigger than any number that can possibly exist and I urge you to take that seriously in forming theories of the universe do not please talk to me about infinite number of galaxies or infinite number of universes because even if that were true it's not a scientific statement because you can't prove it to be true and I would like this institute to be doing stuff which is truly scientific I don't know if we want to have a very very brief session question or not otherwise the speaker will be around for interacting with all of you so I think that we can close the session now there is a party that I can see up there and I okay, there is an infresco up there