Théorie

A space-based laser interferometer, pioneered by NASA's LISA concept and now a ESA cornerstone mission, will enable direct detection of gravitational waves at lower frequencies than LIGO, without being limited by seismic noise. Perhaps the most intriguing source for LISA is the stochastic gravitational wave background produced by turbulent plasma motions in an early-universe, particularly at the electroweak energy scale.

In the first half of this talk, I will discuss how binary systems can be used as dynamical detectors of gravitational waves (GWs). Since the passage of GWs through a binary perturbs the trajectories of the two bodies, we can infer the presence of a GW signal by searching for changes in the binary's orbital parameters. In the presence of a stochastic GW background (SGWB) these changes accumulate over time, causing the binary orbit to execute a random walk through parameter space.

I will present a bit more extended version of the talk that I gave recently at the TAUP2021 conference, with overview of the recent developments in the multi-messenger astronomy.

Black holes (BHs) cover a wide range of mass: from the stellar BH binaries detected with LIGO / Virgo to the massive BHs residing at the center of galaxies. Both these populations will be detectable in future by LISA at low-frequency. In this talk, I will provide a general overview of the current detections from LIGO / Virgo, describing the current state-of-the-art and I will highlight the potential of the LISA mission.

The dawn of gravitational wave (GW) astronomy has enabled new probes of dark matter. In particular, the formation and abundance of primordial black holes (PBHs) can be probed through GWs. In this talk I will discuss different ways how GW observations can be used to probe PBHs and I will review the implications of LIGO-Virgo observations on PBHs.

Gravitational waves (GW) can be used to probe various epochs in the early Universe. In this talk I will discuss about the production of Gravitational waves in a particular model of inflationary magnetogenesis. In this model, we require a low energy scale for inflation and reheating (reheating temperature, TR < 104 GeV) and have a blue spectrum of electromagnetic (EM) field which peaks around the horizon scale of reheating.

Among the sources which the Laser Interferometer Space Antenna (LISA) will observe are the signals from Massive Black Hole Binaries during their inspiral, merger and ring-down phases. To estimate physical parameters of these systems and their localisations, one has to perform some form of Bayesian Inference. The most common approach to do it is through defining a likelihood function and producing posterior samples with some form of sampling technique. The disadvantage of such sampling methods is that they are slow.

In this talk, a tale of two separate studies on gravitational waves (GWs) will be briefly presented.

Gravitational waves have a periodic effect on the apparent positions of stars on the sky. This effect can be quantified and hence ultra-precise astrometric measurements (like the ones from Gaia) can provide a new method to search for gravitational signals.