 Dobro. To je zelo več zelo, na obzervaciji in izgledanje. Zelo je zelo, da počutimo to zelo. Zelo da boš zelo, da smo počutili, da počutimo zelo, gravitacijne zelo. To je zelo, izgledanje, izgledanje, izgledaj, da se se skupaj vzodil, da se predstavimo, da je to zgodno, in daj na odgledaj vzodilom. Ja se predstavim, da sem svetil, da pričajno gledanje z vsega odgleda predstavima, da ne bil vzodilje, kako ustavili odgleda vzodilom. In ste pričaj, da lahko vzodil je, kaj smo imeli, da imamo prvne detekcije. Zdaj se pripravljali base za druga generacija do detektor. Zdaj smo pripravljali za druga generacija. Zdaj smo pripravljali, da smo pripravljali za druga generacija, ker Ligo je jedna z gravitationalnih vstupov, z terferometrij. Zdaj smo pripravljali za september. Virgo je in 2016. Zdaj smo pripravljali zdaj se, da imaš zvrdu, da imaš zvrdu, da je zgravitacija z gravitationalnih vstupov. Zdaj smo pripravljali zdaj se, da imaš zgravitacija z gravitationalnih vstupov. Zdaj smo pripravljali za september. Izgravitacija z gravitationalnih vstupov je z vstupov, da imamo začinev, da ne odrvali z vstupov. Zdaj smo pripravli, da se všeč kot nekaj z glasbenju očustov. Zdaj, da izgravil do vstupov, danes do z defenderov sajturemi slučanje kosmic strings, supermassive black coil binaries, stellar mass compact object binaries, spinning neutron star, core collapse of mass star. So we have a totally new messenger to study this object. We will focus to the spectrum from nanohertz to 10 to the 3 hertz. And to observe these gravitational waves coming from these sources, we have very different detectors that go from Pusa timing array, space detector and ground-based detector. These are the astrophysical sources that we expect. And here you can see frequency and characteristic strain. Characteristic strain is without dimension, give us the length change that our sources produce when they pass, when gravitational will pass. And they represent the amplitude of the sources. And they are the square root of the energy emitted in gravitational waves. So starting from the lower frequency, we have as most promising sources the stochastic background that is given by the superposition of a signal from supermassive binary and cosmological background. Then we have the supermassive black coil binaries. Here we are talking about the object with a mass of 10 to the 9 solar masses. Then we go in the range observed by this one, in the range observed by the satellite. And here we have mass, we can have extreme mass ratio in spiral in which we have a supermassive black coil of mass larger than 10 to the 6 and stellar mass black coil that is orbiting around. And then we have massive binaries with mass around 10 to the 4, 10 to the 7. And also galactic white dwarf binaries. And then in this regime we have the stellar mass black coil and we can have core collapse of supernova or rotating neutral star sources. What you can see is that if we go to lower frequency, we have more massive object with respect to higher frequency and the amplitude of this object is higher. These are astrophysical sources also from the point of view of the signal that they emit are very different. We have sources that for which we know very well from GR, the waveform that they emit. But there is also sources like for example supernova for which we don't know well the waveform. So we can consider then unmodel sources. So the searches for this object is different from the one that we know very well the waveforms. And here are the sources. So you can see that the amplitude increases with mass. But we need to compare this with the sensitivity of the instrument that we have now and that we will have in the near future. So starting from here, here is the regime of pulsar timing array. So we can use the pulsars, in particular the millisecond pulsars. We know about now 300 millisecond pulsar from radio and gamma ray observation. And we cannot use all of them for this type of studies. But we can use the pulsar arrival of this pulsar to see if a gravitational wave is passed through them. Because the gravitational waves disturb, influence this pulsar timing arrival. And we know that millisecond pulsar are very, very precise clock. So if the gravitational wave pass, we have residuals between the pulsar time arrival and observed with respect to what is the prediction. If we have only one pulsar, we cannot say nothing because there is also intrinsic noise in each pulsar. And so we need many pulsar that works as an array. For each of them we evaluate these residuals. We correlate the residuals. And in this way we are able to estimate to see if there is this gravitational wave that pass through them. So we can consider the pulsar timing array as a big galactic scale interferometer. And now this is the sensitivity of the European pulsar timing array. And so there are these programs in which many antenna observe the skies and point the pulsar. The pulsar useful for this type of work are the ones that are very bright and that are very stable. And to improve this sensitivity, we are not very distant, but to improve the main thing is to increase the number of pulsars to do this type of work. So to increase the number of pulsars in the array. And in the next year we will have a new instrument that is an SKI-A. And people expect that at high frequency we will observe many new pulsars. And so we can increase the number of these pulsar that are useful for this type of searches. And so people think that in SKI-A we start in full sensitivity around 2020 so that in the next 10 years this type of instrument will be able to observe. Someone say also before and now they are developing the technique to improve and to try also to better this sensitivity. Then we have this part so about this I can say this is you can go there there is the paper and there is what they assume for the stochastic background but they assume some model so it's not so I cannot say this is all the stochastic background or they assume some model for this. So here is the place of space satellite and here we need so also here what happens is that we need to observe these sources we need to use a technique that is based on interferometers and the harm of the interferometers in this space satellite are around 10 to 9 meters. The first project was Lisa about this space satellite able to detect gravitational waves and the idea was of three satellites in which in each of them there is a test mass and the laser beam within these three satellites and then the project was a NASA European project then the NASA decided to go out from this project and so now it's a only European project that is calling Lisa it's only two satellites and the distance is I think Lisa was 5 per 10 to 9 meters and he Lisa is 10 to 9 meter. Lisa is a very good way to the test gravitational way because there are binary sources that we know that are in the sky so you can point them and observe directly and wait integrated in time and so observe the gravitational waves these satellites are very good with respect to the ground-based detector because you remove completely the worst noise for the ground-based detector that I will show you better later that is the seismic noise so in this space you have not seismic noise it's extremely good in this space you can have a background that is given by the superposition of the unresolved sources for example the white dwarf binary sources but you don't have seismic noise so what is the prospect for Lisa so Lisa will be evaluated to be launched in 2034 not very nearby but this year is very important because the science of Lisa is something that is very good and everyone recognizes that it is extremely good what Lisa can we do but the technology satellites are very difficult and also to think about test mass and satellites divided by many many kilometers that exchange last beam so it's a new technology and this year there will be the pathfinder so there will be a very small Lisa but that will try to test the technology so I think it's a very important step also for the acceptance of this project and then we go to the one more familiar for me that is the ground based detector this is the initial ligon virgo and you can see here this is the binary system of solar mass compact object this is supernovae and this is pulsar so we were very nearby to detect something and I will show you why we didn't detect nothing that is mainly linked to the rate of these type of sources but this is the future the nearby future so this is advanced ligon and virgo and I will show you in which way we will arrive to this sensitivity course here on the top I put all the detector that will contribute to the advanced network and here we show better this plot because it's something very exciting because it's a picture of few days ago the supernovae is here I will show you later because it seems it seems that from the last simulation that the energy emitted by supernovae is very small and so for the initial ligon virgo the maximum distance was about 10 kPa so very nearby also for the advanced detector for some model we have a distance that is within our galaxies there is more optimistic model that I will show you later better that predict larger distance but typically the supernova is expected to be seen in the local galaxies not very distant and so this is very exciting because it's a picture of it's a plot of the sensitivity curve of ligon because ligon is now in the commissioning phase I told you that it will start to observe in September and the things are going very, very well for the commissioning and they already arrived to a distance for a binary system that is better than what they expected before ok, so I will go to the first generation of ground based detector this is only to remember you that we are almost 100 years since Einstein predicted this new type of waves so gravitational waves they are generated by mass distribution with time varying quadruple moments they are propagating at the speed of life and they change the distance between stationary inertial mass and this is the way we use this this change in length to detect them according to GR they have two independent polarisation states and each signal can be described as h as a linear combination of h plus so these two polarisation h plus and h cross we know that they exist because we know in a indirect way because we know that we have this this was the first binary pulsar discovered and looking at these binary pulsars and we make many observations this plot is very interesting because we have observations from 75 to 2000 also now and these are all the observations so we have these orbiting stars they lose energy and there was a prediction by Einstein about the energy lose in gravitational wave by this type of system and you can see the line you don't see the line is not clear but the line is perfectly under the observation and so this is a very strong proof of their existence but it's really very hard to detect them because they have a very weak interaction with matter is the reason why they are so important to see them because they are very powerful probes of regions that are opaque to photons with them we can directly I don't know estimate mass spin things that typically we estimate only in a indirect way by photons but the same reason for which they are so interesting is the same reason for which they are very very difficult to detect so these are the most promising sources binary system they emit gravitational waves the gravitational waves deform space this is a cartoon and so the displacement is proportional to the length you see you have a delta L that is proportional to L and ht and this is constrain doing not to detect very very small I will show you later how much small displacement yes this come from from Michelson we can use interferometers and we can use laser light beam so we have changing lens if you are able to measure the effect on the light of this displacement we can measure the gravitational waves in particular this is a simple way in which we can represent an interferometer here we have two mass we have two mirror, suspended mirror that are our test mass here we have a laser the laser emit a light here the light is divided into the two mirrors into the two arms and if there is the gravitational wave that pass we can have different light different arms and so when the light go here and come back here we have some light that go to the photo diode if no gravitational wave pass through them the length of the arms are the same so when the light come back there is destructive interference so we don't have light to the photo diode so I give you some number if we take a neutron star binary at the distance of 15 MPa and we want to evaluate this is the strain so delta L over L this is the target sensitivity for this type of sources at 15 MPa second is 10 to the minus 22 we are able to detect them because we have these kilometer interferometers and this kilometer arms interferometers are able to measure length change of the order of 10 to the minus 90 meter and this was proved by the initial eigenvirko so we are able to measure the order of magnitude length change smaller than the size of an atomic nucleus and now I will show in a very simple way the first generation that proved this and so here you have again frequency against this is amplitude this is a strain in a different it's a bit different strain with respect to the one that I show you before because this is the square root of the power spectral density is the power is the amplitude density is so the power divided by frequency is another way to show the strain and it's useful mainly for the sources that there are many sources that change dramatically their frequency the power in each frequency when they are in the band of eigenvirko and so this is the sensitivity of the initial eigen and this is an example of neutron star, neutron star at 50 megaparsec this is the merger this is the spiral the last phase of the spiral more or less the last 20 seconds of the spiral and so in the band of lego for neutron star, neutron star the main region is the region detectable is the one of the spiral so this is what I show you before we have this mirror in reality in the arms we have two mirror and I show you why and the photodeod and the laser machine so this is the first noise that we have in this detector so the input power is 10 watt more or less and this power is increased to 15 kilowatt this is thanks to this to this two mirror because they are the so called power recycling cavity so when the light is here the light go back and forward to these harms and this cavity is an amplitude resonance created an amplitude resonance amplification so you can consider the power of our laser 15 kilowatt so one of the main noise source is the quantum noise the quantum noise is due to the random arrival of photons and this generate the so called shot noise and also generate radiation pressure on the mirror if we improve if we increase the power of the laser what happen is that we can reduce a lot the quantum noise here and it is what is happen now with the second generation but at the same time if we increase the power we increase the radiation pressure on the mirror and so here you can see that in the second generation we have a higher quantum noise so at high frequency we can reduce a lot the quantum noise so to increase sensitivity we have two way one is to reduce this noise by increase the power of the laser and the other is to build very very long interferometers that is not so easy because this one are kilometer 400 kilometer and 300 kilometer and so sorry 3-4 kilometer and so increase to 100 kilometer is really very difficult what pressure radiation is the power of the beam that this is the mirror and so it is a pressure on the mirror and this create vibration and this create this many at low frequency this very big noise in this case if you have a higher power you directly have a higher pressure and I show you later how much increase here the the mirror that people use now in the second generation are very good for this so is the structure of the mirror mainly with respect to the to the past with the past mirror it would not be possible to have higher power higher power laser this is the second source of noise that is the seismic noise this create like a wall at low frequency this is due to the random motion of the ground that is produced by car by wind, by people around interferometer in some moment this background increase a lot for example when there are earthquake and when there are for example ocean waves sea waves and in the first generation what happen is that you have to stop the interferometer and then wait that every come back in a stable way and then open again the interferometer for the future this is not possible because the power of the beam is extremely high and so if you stop the interferometer and then you open again the interferometer you can keep you can lose a lot of time of observation and so the way to reduce this noise and also to avoid these close of the interferometer is to have a very sophisticated control of this type of noise and Virgo was very good also in the first generation because over the mirror that is suspended there is a 7 meter column of pendula and each of them are able to filter seismic noise in all direction so to reduce this noise you have to build a very good system control these are the third noise that is the thermal noise and this is due to the I don't know increase on temperature this create excitation of the pendulum and are vibrations so due to temperature increase but are due also to when the mechanical quality system is not really very good and so in the future there are a lot of attention to make a very stable mechanical system to reduce this also the thermal all this system is in vacuum the vacuum is about 10 to the minus 7 tor and this is due to the fact that the light is not to interact with the molecule that can perturb the light these are the current interferometers so we have LIGO, the two LIGO in the United States we have Virgo and Geo so LIGO is a 4 kilometer harm array interferometer Virgo is a 3 kilometer so there is a bit of difference and then we have Geo and Geo is smaller because is 600 meter and Geo is typically used for technological test while these three work in the past together as a network so this is the sensitivity course so this is LIGO this is Virgo the difference here is due to the different length of the harms here you can see that Virgo was very good at low frequency for the seismic control and this is Geo you can see this peak this peak are due to vibration of the suspension system that are due to the environment to the electronic magnetic disturbances so these peak are typically of this type of sensitivity course I think that I didn't say you before is that there are also in the noise some transient event and that are linked also to earthquake also to many environmental disturbances and this transient event that are a lot mimic the transient sources so over this course over this peak over the noise we have many of this of this transient event that are very similar to the signal and that require a very deep study to be removed and to be controlled so the advanced we will have more laser power you can see here the number so we will arrive to 1 megawatt so it's really a lot so this is the previous plot that I show you you can see that the quantum noise is reduce a lot but we have an increase here the radiation pressure this is what we will be obtained with thermal noise with a better mechanical quality and we will suspend the mass with glass fibers and so on this is what we will obtain with a better seismic isolation and so this is what we expect this was the sensitivity course for a neutron star neutron star the sensitivity course and I told you that neutron star, neutron star we was able to detect them up to 50 megaparsec now we will be able to detect them up to 150 megaparsec so we will have an increase in sensitivity of a factor 10 in distance that correspond to a factor 10 to the 3 in volume so 10 to the 3 in the number of sources that we will be able to detect now I will show you why it is important to have a network and not only one interferometer and the main reason is the directional sensitivity so this is the antenna pattern of this type of interferometers the sensitivity, this is the plot is this is the antenna pattern is a pinets shape and you can see that these objects so are able to monitor all sky they are nearly omnidirectional the only place is here where we have a bit lower sensitivity and in particular this is the two arms so if we have a source in the plane with the propagation in the plane of the detector and 45 degree in this case we have a null sensitivity but in general is a very good all sky monitor I remember you that differently from the electromagnetic the hurt is transparent to gravitational waves so we can detect from everywhere gravitational waves but this type of detector have not a good directional sensitivity so it's not a pointing instrument so it's very difficult to understand where come the signal where is the direction of the signal they have a very very poor angular resolution that is about 100 degree and this is the reason why the main reason why it's important to have a network because in this case with a network we are able to determine the sky position of the gravitational waves sources by triangulation so what we do is to measure the difference in the signal arrival times at the different network site and this is for two interferometers and in particular the region of constant delay is a annulus in the sky when we have two detector and this annulus is concentric to the baseline of the two detector and with three detector that is the way in which we can have a good sky localization is the intersection of these three annulus and in particular we have so where they intersect here and here so we have the real position of the sources and also we have the image the mirror image of the real position of the sources and with respect to the plane of the three interferometers so these are more or less if we consider that the lambda of gravitational wave is very big and this is the distance more or less the distance between two interferometers like in Virgo the angular resolution is 60 degree but we can improve with the interferometers and what you can understand is that from here that if we have longer baseline and the network of many many detector all around the world we can clearly improve a lot the sky localization capabilities we have other benefits from using a network we can increase the sensitivity and the sensitivity increase with the square root of the number of the interferometers we can have a larger observational time because each interferometer has a duty cycle so a period in which they don't observe and so if we have a network and we can at least have to detector on and so we can increase the observational time is also more useful to make the allow better to make the parameter reconstruction of the parameter of the sources and is also useful for the things that I told you before that we have this a lot of these glitches in the noise and so we can remove these glitches because they they are not correlated between the different interferometers so Virgo and LIGO have signed in the past in agreement for full that exchange and for a joint analysis of the data and this is what will be also for the future and so LIGO and Virgo will observe the sky as a single network and here I put some number for the sky localization capability if we take a neutron star neutron star with a signal to noise ratio of 7 we will have for a source in the best case when the source is face on with respect to our detector is when the source is over so is is directly over the plane of the detector we will have a sky localization of 20 square degree and a medium volume of 40 square degree so when we say good sky localization you have not to think absolutely to the electromagnetic for the electromagnetic point of view this is a very very poor sky localization this is the near future the near future we will have for the three interferometers but we have also two project indigo that is one of LIGO and for in and for that there were in the past two interferometer one of them will be moved to India and in 2020 we can have another interferometer in India and then we have Kagura in Japan there is two phase the first phase is observation that will start in 2018 this is an underground detector to reduce the seismic noise and is also think to be cryogenic but this will be in a second phase after 2020 so now we go to the astrophysical source detectable by ground based detector and some signs result from initial LIGO in Virgo and the prospects for the advanced detector so we have different type of sources one of them are the ones that give rise to transient event transient gravitational wave signal and these are signal with a duration in the detective sensitive band that are short and shorter than the observation time and that cannot be reprodu, reobserve the second time the typical example are the coalescence of compact objects so stellar mass black hole so we can have neutron star neutron star or neutron star black hole or black hole black hole coalescence or we can have also core collapse of mass star these are the compromising transient sources for this type of sources we know very well the waveforms mainly in the spiral phase that I show you before that for neutron star, neutron star is perfectly in the band of the detector and we know also the energy emitted that is 10 to the minus 2 stellar masses for square light velocity square so these are what initial LIGO in Virgo was able to do that is to observe binary containing in neutron star so neutron star, neutron star, neutron star black hole up to 50 mega parsec this number is the best distance the best distance is obtaining the place where your detector is more sensitive for the better orientation of your system that is phase on so the orbiting plane perpendicular to the line of sight and the likely rate at this distance the astrophysical rate that we expect I will show you that this rate are very very uncertain but in any case is 0.02 so very very low so this is the reason why we were not able to detect nothing up to now for the core collapse of masses star in this case the waveform is very uncertain we don't know the asymmetry of the explosion it is very difficult to simulate also the microphysics in this explosion and the most recent 3D simulation from christianot give an energy emitted in gravitational waves that is 10 to the minus 8 so very smaller with respect to the binary system there are more optimistic models that predict 10 to the minus 4 so as I told before we expect to detect these sources in the past we expected to detect these sources within our galaxies in the future in the local galaxies this is what will happen in the future so Laigo I show you that give rise to a density is a distance improvement of a factor 10 that correspond to a factor 10 to the 3 in the number of detectable sources here I indicated the rate for binary system and you can see these are the rate what we call the more likely rate and you can see here that what we will expect in full sensitivity for Laigo and Virgo so Laigo and Virgo as a network is more or less one event per week but these rate are extremely uncertain and I will show you the way in which you can estimate the rate but if we believe to this number we are really very close to observe a lot of gravitational signal here I also put some number on the distance up to which Laigo and Virgo will be able to observe the system these number are the so-called is the distance obtaining obtained making an average that take into account the sensitivity of the network and also that make an average on the orientation of the system and you can see that we will see neutron star, neutron star up to a distance of 200 megaparsec and I will use this number a lot in the lecture of tomorrow to show you what we expect also from the electromagnetic point of view from this type of sources so for the core collapse of massive star there is the problem that I told you before we don't expect a lot of energy on it there are optimistic model these optimistic model are model in which during the explosion there could be some fragmentation of the core collapse of the core that are collapsing or we can have some instabilities in the accretion disk I will show you tomorrow that supernovae are associated to long gamma rebars and in this case you have this unstable accretion disk and this instability can create a higher gravitational wave emission and in this case we can have also these are extremely optimistic also to arrive to 100 megaparsec back a second on the rate how are estimate the rate the rate come from the rate the detection rate come from the expected merge rate of this system and there are different way now to estimate this rate one of them is use the population synthesis code in this code what they do is a simulation in which they the binaries forms and the valve is elated in which they assume some recipe of stellar evolution and you can see here that these different also stellar evolution recipes give rise to very big uncertainty in these numbers and we are not able to constrain these now we are not able to constrain these number a lot because we have from the observational point of view we have only nine star Newton star system observed also one more of this system can allow us to reduce a lot this uncertainty from the point of view of Newton star black coal and black coal black coal we never observe them from an electromagnetic point of view and so we this one black coal black coal we also don't expect to observe electromagnetic but this yes it's impossible really to reduce this uncertainty because we are not helped from the observational point of view now there are also different type of simulation this simulation are hand body simulation and Monte Carlo simulation that focus on the environment that seems very important for this type of system and focus on global cluster and young star cluster here we have higher density of stars so higher density of this type of object of compact object we have dynamically exchange and we can produce more more of this system and so we can say that we take into account the fact that in this case we don't take into account but the number are in this case very similar and also the range is is very big, is very large so the uncertainty are very large now we have also another way to estimate the rate the merger rate but also this one has a lot of uncertainties that is this one through gamma ray bars if you assume that I will talk more tomorrow about gamma ray bars but if you assume that gamma ray bars that we observe in the sky come from neutron star, neutron star we can try to estimate the neutron star, neutron star merger rate but in any case you can see that this plot show many hoard so it's really very difficult to to restrict to constrain this rate of merger this is per mega year this is for mega parsec square and mega here sometimes this rate are given in milky wave equivalent instead of mega parsec per cubic mega parsec this one are detection rate so in this one you have to take into account the volume so you can take so this one, this number here are exactly these here come exactly from these here and what you do is to evaluate the merger rate for equivalent milky wave galaxies and then you extrapolate to your volume to the volume up to which your detector is sensitive so they come exactly from here so it's ok the rate is uncertain we hope that the more likely is the one that will give us many detection but what I want to say is that in any case also to have non-detection from the astrophysical point of view is very important because also to have I don't know two years of non-observation of gravitational wave of full sensitivity will give us from an astrophysical point of view put strong constraint on the stellar evolution model so these are the binary system here I have I think that the sound is not possible to listen in any case this is what happen and I go on so the signal is embedded in this very bad noise I have also the sound but it's impossible to listen so we have this, you can see here this is the signal and this is the noise so it's very complicated also from the point of view of the analysis to extract this signal from the noise and for the coalescence of compact object what we use is this mainly this phase we know the waveforms the waveforms depend on intrinsic parameters and extrinsic parameters the intrinsic parameter are mainly masses and spin of the system and then we have also eccentricity neutron star compactness intrinsic parameter that are location, distance, merger time and system orientation with respect to the observer but we use a lot and they'll pass a lot to use the knowledge of the waveform and so what we do is in the detection phase we know waveform and we use match filtering we use template use not all the parameters so we fix the parameters and we use template that cover big range of masses and spin and the extrinsic parameter are absorbed in the amplitude and so we make a correlation using these these waveforms this is the first phase of the analysis this is the second phase in which we use the template with all these 15 parameters our waveform with 15 parameters and then so this is a longer take long clearly this analysis and so after the detection we will make this source parameter reconstruction that will allow us to have information on masses, spins, distance sky localization this was with this type of analysis we we run over the data these analysis and what we found was we didn't make any detection and we put some upper limit so the non-detection allow us to put upper limit on the rate and this is what we obtained this is the exclusion region so this is non-detection corresponded to this upper limit on the rate this is for object with a mass between 2 and 25 solar masses for the neutron star this rate correspond to 135 solar masses this is the total masses this is the mass of the component and this is the black hole used for this rate so you can see that we were distant from the astrophysical rate that are the one that I show you before this is what will happen with the advanced detector so we think that we are nearby to the to the detection as I told you before also not observe a gravitational wave allow us to put big constraint on the stellar revolution and so we hope to observe this type of sources to observe for the first time black hole, black hole and black hole neutron star to put constraint on the evolution and also to shed light on the birth and the evolution of black hole and also another thing that is a lot of debate now is the mass distribution of black hole and the only way to know the mass distribution of black hole is through this gravitational wave messenger these are the unmodeled transients we have core collapse of mass star we can have cosmic strings we can have neutron star instability so star quaking and neutron star that are visible in the electromagnetic I will show tomorrow and so these create a non radial oscillation that can give rise to gravitational waves we don't know the waveform so they are very poorly modelled and so we cannot use the mesh filter and what we look for is for excess power so we make all-sky, all-time search for transient for the increase in power in some time frequency region and we look for this excess this is an injection and so the assumption in this type of analysis is the duration of the of the signal that need to be less than 1 second this is I think is between 1 and 100 millisecond and this is the frequency range in which we perform this search frequency to 2000 Hz and we use a lot the network in this case first of all because the network allow us to reduce the fossala rays so these glitches that are not coherent in all the detector and this is an example for example you can see that this is to spike due to the noise and these are due to an injection and so we can remove this type of event that are very similar to these bars this is a result of initial ligon virgo and so the non-detection allow us to put to make this plot that give us the energy up to which ligon virgo would be able to see so if we take a source at 10 Mpa we are sure that the energy emitted we would see an energy of this source is higher than this so if during the observation of ligon virgo there were pulse for example from the galactic center that is more or less this distance we were able to detect them and since the energy emitted in gravitational waves is proportional to the distance to the second we can see that we need a factor, a very high factor more energy for a signal detectable from the virgo here I put this this plot was obtained making injection in the data and injected some transient signal and we use this type of waveform you cannot see here well there I'm sorry the plot in pole other sources these are continuous gravitational wave signal so rotating neutron star can emit gravitational waves can emit if they are asymmetric they can emit quasi periodic waves whose frequency change in a very, very slow way the signal expected from these sources is very, very weak but is a continuous signal and so we can integrated our observation for example for here and try to improve the signal to noise ratio and try to detect this type of event and we performed two type of searches one or sky or frequency and the other one was pointing if you want is not pointing, I explain what I mean but we make a search on the known pulses what we do is to take all the data gravitational wave data but to restrict the parameter search by looking at the same sky position of the known pulses and at the same frequency of the pulses so we use what we know from the electromagnetic point of view the position and the frequency of the pulses in the gravitational wave search and this is what we obtained these are all this point corresponded to pulses and for each pulses we know from the electromagnetic point of view the rotational energy that the pulses lose and we can estimate for each pulses the so-called spin down limit the spin down limit is if we assume that all the rotational energy lose is due to gravitational waves we can say this is the spin down limit this is the is something that we estimated from the electromagnetic point of view and for each of these pulses we have we have these limits so no observation of gravitational waves tell us that the energy emitted from these pulses is lower with respect to this emitted in as a rotational loss and all this point are the spin down limit corresponding to these sources so to each of these sources we have the the so-called spin down limit I want to say you that here are the region of young pulses that one that lose more rapidly the rotational energy and here are the region of the millisecond pulses low frequency here is better Virgo all these pulses were studied by Virgo here is better Laigo and so all these pulses were studied by Laigo for two of these pulses we were able to beat the spin down limit the two pulses are crab and villa you see here this is crab and villa so for these sources we discover that the energy lose the rotational energy lose cannot be explained totally as gravitational waves so we have other phenomena for which our pulses lose rotational energy because our point are lower with respect to these two points these allow us assuming some model also to put some constrain on the ellipticity because the energy emitted in depends on the ellipticity so we know that for crab the ellipticity is less than this number so a very small number and also for villa the ellipticity is smaller than 6 per 10 to the minus 4 so these objects are not very asymmetric this is the stochastic background I am not very expert of this part but so the stochastic background is the superposition of many in current not resolvable sources many of them can be astrophysical so astrophysical from the astrophysical point of view we can have compact binaries rotating neutron star magnetar supernova also very distant but that LIGO and Virgo are not to resolved so we see them as a background or we can have cosmological background so we can have inflections cosmic superstring alternative cosmology and what happens in this case the stochastic background if we have only one detector the stochastic background is a noise for the detector so it is like the noise that I show you at the beginning and so it is really very hard to try to see this noise over the other component to discriminate this noise with respect to the other component of the noise also because it is I show you before it is really very difficult to have a complete knowledge of all the noise of the detector and so the technique to try to see the stochastic background is to use a network again and to make a cross correlation because the noise due to the stochastic background is correlated between the detector but not the noise of the single detectors the real noise so this was what LIGO and VIRGO were able to do and was the surpasses the indirect limit from big bang nucleosynthesis these are the estimated different frequency of LIGO and VIRGO initial LIGO and VIRGO this is the point corresponding to these energy and gravitational waves this is the advanced what we expect from advanced LIGO and VIRGO here if you look at inflection you see that this background is very flat and so the dominant component is the one from astrophysical sources black hole binary neutron stars these are the region of cosmic strings and so with respect to the for example the bisep signal this VIRGO is many order of magnitude higher and also the advanced detector because it is a six order of magnitude and so the main source is that we expect to detect from the advanced also the advanced LIGO and VIRGO is mainly the astrophysical sources for the background or some I don't know action inflection or other things but so we think that the main goal would be to detect an astrophysical background for the advanced detector we have to go at very low frequency or for detection of of cosmological background so we can this is what I will show you tomorrow that is the multi messenger astronomy because this detector will observe the sky with many other satellites that observe in the electromagnetic bands and so we develop analysis that use not only gravitational wave but gravitational wave and electromagnetic information and also we develop we we organize program to combine the observation to make simultaneous observation of gravitational wave network and electromagnetic instrument and so I will show tomorrow this part of multi messenger astronomy you said that the network increases sensitivity how? the network will increase the sensitivity the network increases the sensitivity so the sensitivity improve with the the square root of the number of the detector why? this is due to the come from the signal to noise ratio and so is due to the is due to the way in which you estimate the signal to noise ratio and it is it is very simple so does the position of the network but it is not a great improvement the I can say I think that it is a great improvement to have a network in terms of sensitivity if you think that the main problem is the rate so if you think that the main problem is the rate for you it is more important to increase the observational time so in terms of sensitivity a square root on the number does not increase you a lot the sensitivity so the maximum distance but if you think to the observational time in which you can have a detector horn this increase you it is more important because increase you a lot the rate of detection does the position of the object of the network influence that is why you are moving one to India or no the position of the network does it influence so that you are moving now one to India so it is not it is not that you move one to India but at Enford in the past there was two detectors and for the advanced detector we will have only one because to have one detector there does not improve a lot does not improve the sensitivity but does not improve the sky localization and so the idea was to move one of these two that was in Enford to India longer baseline give you a better sky localization so to have a detector in India would be extremely good I will show you tomorrow the difference between sky localization with LIGO India and without you can go from hundred of square degree of the LIGO and VIRGO to about ten, twenty square degree so there is I was thinking about an analogy with optical interferometer is there some analogy in the sky position in the direction larger baseline is for you a better sky localization very good would be one in the south hemisphere so there was a project of one interferometer in Australia that is very good also for the sky coverage any other question? if not we please one from the north and how usually do you solve this problem what method do you apply please is when you know the way from you can use this mesh filter and in the other case when you have a model sources is to search for this excess power with respect to the noise and for a model sources that are for example transient sources what we do for example for the noise is to use this time shift so you to understand what are the glitch the transient sources that are not correlated with respect to the one that are really signal so there is very deep and statistical estimate of the noise in the case of mesh filter you reduce a lot the problem of these glitches but you can make this only for the sources for which you know very well the waveforms some years ago I hear about some kind of spheres that are made in order to observe some kind of polarization of gravitational waves I hear something about this sphere in Brazil but I don't know what happened or what with the results and if they prove that they can observe something about this I don't know if now they are activating that there was one in Brazil that worked for this and I think that the system is similar to the bar so you have this this change they try to observe, right? they can observe also the polarization because it's this but I think that the sensitivity of this type of instruments are really very local so very nearby something that happens in the galaxy so I don't know, it's super not in the galaxy maybe that you can see but I don't think that the sensitivity is high like the bars can we get back to the first slides when you put different detectors, please yes, the last one when you put so these are ok, that's ok the others the first two are what are in this space on ground or what the first two so this one is the European pulsar timing array this is Heliza the European Liza yes these are gravitational wave and they are on the ground no so this is a space satellite and the others use pulsars pulsars in the sky the two are in space these two these are in space you observe from ground with the radio antenna but you use the pulsars as instrument to measure the gravitational waves so your array is given by the pulsars ok, so because I was wondering why the shape is so sharp here and the second one should be also more smooth because there is no sysmic and thermal I think ok, I don't know why this is so really I don't know but yeah year and year you have no sysmic noise this is something very important for the sky with respect to to this to the one that are in the ground but you have other type of noise and so I really don't know why it is in this way but yeah main noise will be the background noise the signal for example from a white dwarf that you are not able to see like you have many unresolved signal all together so you have an astrophysical noise sorry maybe to just a comment about the cusp on the pulsar timing maybe that's just because if you look at the frequency it's so low that it's probably just limited by the pulse probably slowly marches to the left if you are willing to do a 10 year observation but that's probably where it could be yeah any other question ok, if not let's thank Marika and