| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Tanmay Vachaspati (Arizona State University, Tempe, USA) |
Introduction to Topological Defects I will introduce some aspects of topological defects in three lectures with a focus on their role in cosmology. In sequence the lectures will be on domain walls, strings, and monopoles. |
||
| 11:30 to 13:00 | Ashoke Sen (International Centre for Theoretical Sciences, Bengaluru, India) |
Gravitational Wave Tails from Soft Theorem If a set of massive objects collide in space and the fragments disperse, possibly forming black holes, then this process will emit gravitational waves. Computing the detailed gravitational wave-form associated with this process is a complicated problem, not only due to the non-linearity of gravity but also due to the fact that during the collision and subsequent fragmentation the objects could undergo complicated non-gravitational interactions. Nevertheless the classical soft graviton theorem determines the power law fall-off of the wave-form at late and early times, including logarithmic corrections, in terms of only the momenta of the incoming and outgoing objects without any reference to what transpired during the collision. In this short review I shall explain the results and very briefly outline the derivation of these results. |
||
| 14:30 to 15:15 | Andrew Long (Rice University, Houston, USA) |
Gravitational Waves from Chiral Plasma Instability in Standard Cosmology In the primordial plasma, at temperatures above the scale of electroweak symmetry breaking, the presence of chiral asymmetries is expected to induce the development of helical hypermagnetic fields through the phenomenon of chiral plasma instability. It results in magnetohydrodynamic turbulence due to the high conductivity and low viscosity and sources gravitational waves that survive in the universe today as a stochastic polarized gravitational wave background. In this article, we show that this scenario only relies on Standard Model physics, and therefore the observable signatures, namely the relic magnetic field and gravitational background, are linked to a single parameter controlling the initial chiral asymmetry. We estimate the magnetic field and gravitational wave spectra, and validate these estimates with 3D numerical simulations. |
||
| 15:15 to 16:00 | Raghuveer Garani (Indian Institute of Technology, Madras, India) | Cosmological particle production | ||
| 16:30 to 17:15 | Hu-aike Guo (ICTP-AP Beijing, China) |
Hearing the Sound from Cosmic Phase Transitions In this talk I will discuss gravitational waves from the sound generated during the cosmic first order phase transitions. I will discuss some of the recent developments in the determination of the spectrum from this source. I will also discuss how to detect such gravitational waves with ground and space based detectors. |
||
| 17:15 to 18:00 | Yann Gouttenoire (Tel Aviv, Israel) | Baby Universe from Domain Wall Networks |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Tanmay Vachaspati (Arizona State University, Tempe, USA) |
Introduction to Topological Defects I will introduce some aspects of topological defects in three lectures with a focus on their role in cosmology. In sequence the lectures will be on domain walls, strings, and monopoles. |
||
| 11:30 to 13:00 | Ashoke Sen (ICTS - TIFR, Bengaluru, India) |
Gravitational Wave Tails from Soft Theorem If a set of massive objects collide in space and the fragments disperse, possibly forming black holes, then this process will emit gravitational waves. Computing the detailed gravitational wave-form associated with this process is a complicated problem, not only due to the non-linearity of gravity but also due to the fact that during the collision and subsequent fragmentation the objects could undergo complicated non-gravitational interactions. Nevertheless the classical soft graviton theorem determines the power law fall-off of the wave-form at late and early times, including logarithmic corrections, in terms of only the momenta of the incoming and outgoing objects without any reference to what transpired during the collision. In this short review I shall explain the results and very briefly outline the derivation of these results. |
||
| 14:30 to 15:15 | Andrew Long (Rice University, Houston, USA) | Electroweak bubble wall velocity | ||
| 15:15 to 16:00 | Sulagna Bhattacharya (Tata Institute of Fundamental Research, Mumbai, India) |
Gravitational Waves as a Probe of particle Dark Matter Galactic Dark Matter (DM) particles can get captured inside celestial bodies if they have some non-zero but weak interaction with the nucleons. Due to their significant size and lifetime, these celestial bodies can capture huge amounts of DM particles, and eventually, an overly dense dark core is created. This core can further collapse and form a minuscule Balck Hole (BH) that can eat up the entire celestial body over time and form a similar mass BH. Depending on the DM- nucleon interaction cross-section, this theory can be studied in non-compact stars like the Sun, and Jupiter, and compact objects like Neutron stars (NS). We show constraints on DM parameter space using gravitational wave detectors like LIGO (ground-based) and LISA (space-based), by studying low-mass (1-2.5 M_{solar}) compact object mergers and close stellar binaries in their inspiral phase respectively. We will argue how these gravitational wave experiments can work as a direct detection experiment for DM searches. |
||
| 16:30 to 17:00 | Nilanjandev Bhaumik (International Centre for Theoretical Physics Asia-Pacific, Beijing, China) |
Induced Gravitational Waves and Primordial Black Holes The recent detection of very low-frequency stochastic gravitational wave background (SGWB) by Pulsar Timing Array collaborations like NANOGrav and IPTA has initiated many studies to understand the possible cosmological origin of such a signal. Amongst other candidates, the existence of primordial black holes (PBHs) in the early universe has also been pointed out as a very promising channel to generate such a signal. The most studied mechanism in this context is the formation of near-solar mass primordial black holes which leads to an amplification of SGWB in the relevant frequency range. This particular mechanism suffers from the overproduction of PBHs which can be overcome if we consider the PBHs to form during an extended non-standard reheating phase, instead of the standard radiation era. On the other hand, the resonant amplification of SGWB due to the domination of very low mass PBHs (10-10^5 g) before BBN can also effectively explain the NANOGrav data. We compare these different channels of SGWB generation with Bayesian analysis and find both these scenarios are statistically favored when individually compared with the astrophysical supermassive black hole binary merger model. |
||
| 17:00 to 17:15 | Subhasis Maiti (Indian Institute of Technology, Guwahati, India) |
Constraining Inflationary Magnetogenesis and Reheating via GWs By utilizing constraints on primordial magnetic fields (PMFs), their contributions to secondary gravitational waves (GWs), and recent results from pulsar timing arrays (PTAs), we establish bounds on the reheating epoch. Our analysis reveals that the combined spectral density of both primary and secondary GWs (generated by PMFs) can generally be characterized as a broken power law with five distinct indices. The spectral behavior of the GWs varies significantly based on the equation of state (EoS), resulting in unique shapes that can readily distinguish different scenarios. Furthermore, we demonstrate that the GWs produced are sufficient to account for the recently observed signals in PTAs under specific reheating scenarios. Importantly, these signals are also likely to be detected by future GW observatories, enhancing our ability to decode the early universe and shed light on inflationary magnetogenesis mechanisms. |
||
| 17:15 to 17:30 | Dhruv Ringe (IIT Indore , India) | Domain wall constraints on the doublet left-right symmetric model from pulsar timing array data | ||
| 17:30 to 17:45 | Koustav Mukherjee (Indian Association for the Cultivation of Science, Kolkata, India) | GW and N singlet leptogennesis |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Subhendra Mohanty (Indian Institute of Technology, Kanpur, India) |
Introduction to Gravitational Waves I will give an introduction to Gravitational Waves from the perspective of Field Theory. I will then go on to discuss soft-graviton theorems and memory effect. I will also cover the theory of Stochastic Gravitational Waves and derive the Dellings-Down relation. |
||
| 11:30 to 12:15 | Francesco Rescigno (National Institute for Nuclear Physics, Rome, Italy) |
Primordial Black Holes from the Supercooled Phase Transitions with Radiative Symmetry breaking First-order phase transitions, which take place when the symmetries are predominantly broken (and masses are then generated) through radiative corrections, produce observable gravitational waves and primordial black holes. I illustrate a model-independent approach that is valid for large-enough supercooling to quantitatively describe these phenomena in terms of few parameters, which are computable once the model is specified. In particular, in this talk, I describe the abundance, mass and spin of the produced primordial black holes in terms of the above-mentioned parameters. I identify regions of that parameter space allowed by the observational constrains where primordial black holes can account for a fraction of the (or the entire) dark matter abundance. |
||
| 12:15 to 13:00 | Erica Ivonne Zavala Carrasco (Swansea University, Swansea, UK) |
Probing String Cosmology with Gravitational Waves In this talk, I will discuss a couple of string theory-inspired models that predict an enhancement of the primordial gravitational wave spectrum during and after inflation. These models offer unique opportunities to probe the physics of the early universe and quantum gravity through potentially detectable signatures in current and future experiments. |
||
| 14:30 to 15:15 | Priyotosh Bandyopadhyay (Indian Institute of Technology, Hyderabad, India) |
Perturbativity, Higgs mass FOPT and Gravitational wave with inert models We discuss the possibility of attaining the SM Higgs mass along with the perturbativity of the dimensionless couplings for inert models The possibility of first order phase transition demands a lower bare mass to the extended scalars. The possibility of dark matter in these models often demands the SM higgs portal coupling or combinations to be low. The possibility of having a charged Higgs boson also puts more collider bounds. We show the allowed region of parameters for the inert models. |
||
| 15:15 to 16:00 | Graham White (Southampton University, UK) |
Why quantum gravity made me fall in love with domain walls Domain walls are a defect that arises when a vacuum manifold is discontinuous. They are often regarded as a problem - literally the "domain wall problem" - but if you can get rid of them, they could be an interesting source of gravitational waves. If the domain walls result from a breaking a global symmetry, the most common way of doing so always struck me as contrived - having an unnaturally small bias term. Quantum gravity is expected to violate all global symmetries - but the process is generally a non-perturbative process like an instanton/wormhole. This means the effective scale of explicit global symmetry breaking is many orders of magnitude above the Planck scale. This makes gravitational waves from domain walls natural. Moreover, if dark matter is protected by a global symmetry which is violated by the same mechanism, one can acquire an independent measurement of a qualitative feature of quantum gravity. Finally, the domain walls themselves can catalyze primordial black hole production, making quantum gravity the indirect source of dark matter. |
||
| 16:30 to 18:00 | Achamveedu Gopakumar (Tata Institute of Fundamental Research, Mumbai, India) | Introduction to Gravitational Waves |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Achamveedu Gopakumar (Tata Institute of Fundamental Research, Mumbai, India) | Detection Principles of Gravitational Wave Observatories | ||
| 11:30 to 13:00 | Thomas Konstandin (Deutsches Elektronen-Synchrotron, Hamburg, Germany) |
GW from phase transitions In these lectures, I discuss how GWs are produced by cosmological phase transitions. We start by a short recap of gravitational waves and then move to early attempts using pairs of bubbles and the envelope approximation. Next we cover the energy budget of phase transitions and the impact of sound waves. Finally I comment on recent developments. |
||
| 14:30 to 15:15 | Suvodip Mukherjee (Tata Institute of Fundamental Research, Mumbai, India) | Detecting gravitational waves using CMB | ||
| 15:15 to 16:00 | Marcin Badziak (University of Warsaw, Warszawa, Poland) |
First-order phase transitions and darkogenesis in Twin Higgs models I will discuss phase transitions in Twin Higgs (TH) models. Previous studies found that phase transitions cannot be first-order. We show that strong first-order phase transitions (FOPTs) can occur provided that appropriate source of Z_2 symmetry breaking between the twin and Standard Model (SM) sectors is present. I will discuss explicit models in which this can be realised. The strongest FOPTs are found in scenarios with large twin fermion Yukawa couplings and light twin sfermions in the framework of supersymmetric TH models. I will present predictions for gravitational waves. I will also discuss the EW symmetry non-restoration scenario in which the EW symmetry breaking occurs at temperatures much above the EW scale and implications for darkogenesis (baryogenesis from dark sector). |
||
| 16:30 to 17:00 | Achamveedu Gopakumar (TIFR, Mumbai, India) | Ultralight Dark Matter at PTA | ||
| 17:00 to 17:30 | Swagat Mishra (University of Nottingham, Nottingham, UK) | Inflationary Gravitational Waves as a Probe of the Unknown Expansion History of the early Universe | ||
| 17:30 to 18:00 | Indra Kumar Banerjee (Indian Institute of Science Education and Research, Berhampur, India) |
Seeing the invisible with black hole superradiance sourced gravitational waves In this talk I explain a few our works which revolve around the direct an indirect signals of first order cosmological phase transitions. The former consists of the primary gravitational waves created directly from the phase transitions, whereas the later consists of the secondary gravitational waves from the primordial black holes which can originate from the phase transition. These secondary gravitational waves can arise from the primordial black holes from a few different mechanisms such as gravitational interactions, superradiant instability, etc. Furthermore, these primordial black holes can also acquire small initial spin and we focus on their dependence on the phase transition properties. |
||
| 18:00 to 18:30 | Pratyusava Baral (University of Wisconsin–Milwaukee, Milwaukee, USA) |
Measuring Speed of Gravity and Dispersion using GW370817 in Cosmic Explorer Compact binary sources detected during the present observing run would last around a few hours in the band of next-generation ground-based gravitational wave detectors. This source observed from an Earth-centered and Earth-rotating frame, will move on the sky. In this talk, we’ll describe a way to use this apparent motion on the sky to measure the speed of gravity and test a wide array of beyond-standard model theories using a phenomenological dispersion relation. We do a full Bayesian parameter estimation on a typical GW170817-like system with higher modes (which should be detectable in future detectors) to measure the speed of gravity and the dispersion relation. I shall also describe how we do this run in a reasonable timeframe and the constraints that we get using one source with signal-to-noise around 1000 and one 40km Cosmic Explorer. The methods developed are fully general and can be used easily for both multiple detectors and detections. |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Gianmassimo Tasinato (Swansea University, Swansea, UK) | Induced GW and Primordial Black holes | ||
| 11:30 to 13:00 | Thomas Konstandin (Deutsches Elektronen-Synchrotron, Hamburg, Germany) |
GW from phase transitions In these lectures, I discuss how GWs are produced by cosmological phase transitions. We start by a short recap of gravitational waves and then move to early attempts using pairs of bubbles and the envelope approximation. Next we cover the energy budget of phase transitions and the impact of sound waves. Finally I comment on recent developments. |
||
| 14:30 to 15:15 | Suvodip Mukherjee (Tata Institute of Fundamental Research, Mumbai, India) | Learning the high redshift Universe using nano-hertz and hecto-hertz GW background | ||
| 15:15 to 16:00 | Wan il Park (JeonBuk National University, Jeonju, South Korea) | Gravitational waves from thick cosmic strings of a SUSY flat direction | ||
| 16:30 to 18:00 | Mairi Sakellariadou (Kings College London, UK) | Gravitational Waves: the theorist’s Swiss knife | ||
| 18:00 to 18:30 | Sonia Paban (Harvard University, Cambridge, USA) |
Primordial Stochastic Gravitational-Wave Background from a Sharp Small Scale Feature in Multi-field Inflation. Inflation is among the cosmological sources of SGWB. Single-field slow-roll inflation, without features, predicts an $\Omega_{\rm GW}$ that is almost constant in frequency and whose magnitude is well below the sensitivity level of future detectors. However, single-field models with periods of ultra-slow rolling or rapid-turning multi-field models of inflation can source detectable gravitational waves to second order in perturbation theory. For example, a brief, rapid turn in field space is a departure from single-field behavior and sources both a feature in ${\cal P}_{\zeta}$ (at shorter scales than observed by CMB and LSS) and the Stochastic Gravitational-Wave Background (SGWB). We will present evidence that the shape of this SGWB signal is mostly independent of the number of dynamical fields and has an enhanced amplitude sourced by the large isocurvature transient, opening a new window of detectable parameter space with small adiabatic enhancement. |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Parameswaran Ajith (International Centre for Theoretical Sciences, Bengaluru, India) | Astrophysical sources of GW | ||
| 11:30 to 13:00 | Gianmassimo Tasinato (Swansea University, Swansea, UK) | Induced GW and Primordial Black holes | ||
| 14:30 to 15:15 | Thomas Konstandin (Deutsches Elektronen-Synchrotron, Hamburg, Germany) |
GW from phase transitions In these lectures, I discuss how GWs are produced by cosmological phase transitions. We start by a short recap of gravitational waves and then move to early attempts using pairs of bubbles and the envelope approximation. Next we cover the energy budget of phase transitions and the impact of sound waves. Finally I comment on recent developments. |
||
| 15:15 to 16:00 | Ricardo Ferreira (University of Coimbra, Coimbra, Portugal) |
Signatures of domain wall networks: from gravitational waves and primordial black holes to cosmic birefringence In this talk, I will present recent progress in the study of domain wall networks. First, in terms of their gravitational relics - gravitational waves (GWs) and primordial black holes - that might be behind the recent signals observed at Pulsar Timing Arrays. Second, I will discuss the isotropic birefringence effect that domain wall networks coupled to photons cause on the polarization of the CMB, with striking connections to the recent evidence found in the CMB data. |
||
| 16:30 to 17:00 | Ramkishor Sharma (Institute of Physics Czech Academy of Science, Prague, Czech Republic) |
Probing Axion-U(1) Inflation: Gravitational Waves and Primordial Black Hole Formation Axion inflation models are particularly interesting due to their shift symmetry, which protects the axion potential from large quantum corrections. In models where the axion couples to a gauge field, this coupling gives rise to a rich phenomenology, including the production of gravitational waves (GWs), primordial black holes, and primordial magnetic fields. In this talk, I will discuss our ongoing work that numerically explores axion inflation in the regime where a strong coupling between axions and gauge fields induces significant backreaction from amplified gauge fields during inflation. These amplified fields produce high-frequency GWs, which serve as a probe for constraining the coupling strength between axions and gauge fields. Our findings indicate that when backreaction is significant during inflation, constraints on coupling strength due to GW overproduction are relaxed compared to previous studies where backreaction occurs only after inflation. I will also discuss the generation of magnetic fields of astrophysical interest in this model. |
||
| 17:00 to 17:30 | Dibya Chakraborty (Indian Institute of Technology, Madras, India) |
Inflationary Models in Perturbative Large Volume Scenario In this talk, I will discuss a phenomenon called cosmic inflation in which the Universe went through accelerated exponential expansion to solve the horizon problem of Cosmological Microwave Background within a billionth of a trillionth of a trillionth of a second, in the very early Universe. This accelerated expansion, in its minimal form, is driven by a scalar field (inflaton) and it takes place when this scalar field slowly rolls down a potential well. However, the origin of this scalar field and the correct form of the scalar potential remains an open question in cosmology. I will present a string theory motivated model where the inflaton is connected to the geometry of the internal space -- the overall volume of it drives the inflation. In particular, I will present a construction where the overall volume modulus (scalar field) is dynamically stabilized to an exponentially large value only via perturbative corrections, also known as perturbative large volume scenario (LVS). In this framework, the robustness of the single-field inflationary model is checked against possible sub-leading corrections. In the later part of my talk, I will focus on the global embedding of the fibre inflation in perturbative LVS and show how our constructions pose less challenge in realizing a successful period of inflation. |
||
| 17:30 to 17:45 | Indranil Chakraborty (Indian Institute of Technology, Bombay, India) |
Can self-interaction in supernova neutrinos cause changes in gravitational memory signals? Gravitational wave memory is a persistent non-oscillatory shift in the gravitational wave amplitude. Such effects are ubiquitous in astrophysical and cosmological cataclysmic events involving gravitational radiation. In this talk, we turn our attention to the case of a supernova neutrino burst generating gravitational radiation. Previous studies along this line have demonstrated that a neutrino burst in such scenarios gives rise to a gravitational memory signal. Here, we specifically inquire about the alterations to the memory signal when neutrinos emitted from a supernova undergo self-interaction, presenting an avenue for indirectly detecting neutrino self-interaction. |
||
| 17:45 to 18:00 | Kousik Loho (Harish-Chandra Research Institute, Allahabad, India) |
Constraining burdened primordial black holes with gravitational waves We investigate the implications of memory burden on the gravitational wave (GW) spectrum arising from the Hawking evaporation of light primordial black holes (PBHs). By considering both rotating (Kerr) and non-rotating (Schwarzschild) PBHs, we demonstrate that the overproduction of primordial GWs from burdened PBHs could impose stringent constraints on the parameters governing backreaction effects. These constraints, derived from ∆Neff measurements by Planck and prospective experiments such as CMB-S4 and CMB-HD, offer novel insights into the impact of memory burden on PBH dynamics. |
||
| 18:00 to 18:15 | Khursid Alam (Indian Institute of Science Education and Research, Kolkata, India) | CMB Constraints on Natural Inflation with Gauge Field Production | ||
| 18:15 to 18:30 | Debarun Paul (Indian Statistical Institute, Kolkata, India) | Primordial gravitational waves as probe of dark matter and leptogenesis |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 11:00 | Parameswaran Ajith (ICTS - TIFR, Bengaluru, India) | Astrophysical sources of GW | ||
| 11:30 to 12:15 | Bala Iyer (ICTS - TIFR, Bengaluru, India) | History of GW research in india | ||
| 12:15 to 13:00 | Thomas Konstandin (Deutsches Elektronen-Synchrotron, Hamburg, Germany) |
GW from phase transitions In these lectures, I discuss how GWs are produced by cosmological phase transitions. We start by a short recap of gravitational waves and then move to early attempts using pairs of bubbles and the envelope approximation. Next we cover the energy budget of phase transitions and the impact of sound waves. Finally I comment on recent developments. |
||
| 14:30 to 15:15 | Alberto Roper Pol (University of Geneva, Switzerland) | Turbulence GW and magnetic fields | ||
| 15:15 to 16:00 | Gianmassimo Tasinato (Swansea University, Swansea, UK) | Kinematic anisotropies of the stochastic gravitational wave background | ||
| 16:30 to 18:00 | Mairi Sakellariadou (Kings College London, UK) | Gravitational Waves and Fundamental Physics | ||
| 18:00 to 18:30 | Mudit Rai (Texas A&M University, USA) | Imprints of Early Universe Cosmology on Gravitational Waves |
| Time | Speaker | Title | Resources | |
|---|---|---|---|---|
| 09:30 to 10:15 | Mar Bastero-gil (Grenada University, Spain) |
Warm inflation and Gravitational Waves In this talk we will review the dynamics of warm inflation and the effect of dissipation on the primordial spectrum. When inflation occurs in the so-called strong dissipative regime, this effect will lead to the enhancement of the spectrum over all scales. An in particular to large enough fluctuations over the last 10-20 efolds of inflation which on re-entry may form Primordial Black Holes and act as a source for the tensors at second order. We will discuss different realisations consistent with CMB observations, i.e., different combinations of potentials and dissipative coefficients. Typically the enhancement is maximal near the end of inflation, which result in a spectral density of Gravitational Waves (GW) peaked at large frequencies today, in the range of MHz. Although the frequency range is outside the reach of present and planned GW detectors, it might be reached in future high-frequency gravitational waves detectors, designed to search for cosmological stochastic GW backgrounds above MHz frequencies. |
||
| 10:15 to 11:00 | Rajeev Jain (Indian Institute of Science, Bengaluru, India) | Primordial black holes from inflation: dark matter, secondary gravitational waves and imprints from Hawking evaporation | ||
| 11:30 to 12:15 | Debaprasad Maity (Indian Institute of Technology, Guwahati, India) | Minimal magnetogenesis, primordial black holes and secondary gravitational waves | ||
| 12:15 to 13:00 | Yu Hamada (DESY, Hamburg, Germany) | Gravitational waves from charge-carrying domain walls | ||
| 14:30 to 15:15 | Ranjan Laha (Indian Institute of Science, Bengaluru, India) | Searching for dark matter and dark sector particles using gravitational waves | ||
| 15:15 to 16:00 | Fabrizio Rompineve (Universitat de Barcelona, Catalunya, Spain) | Pulsar Timing Arrays and early Universe sources with an outlook for 3G detectors | ||
| 16:30 to 17:00 | Arushi Bodas (University of Chicago, Illinois, USA) |
Seeing highly anisotropic gravitational wave backgrounds from the early universe A stochastic gravitational wave background (GWB) produced in the early universe would necessarily exhibit anisotropies analogous to the CMB. In multi-field inflationary scenarios, anisotropies in GWB could differ significantly from those of the CMB if sourced by a quantum field different from the one sourcing CMB. In these scenarios, however, the more interesting case of highly anisotropic GWB typically comes at the cost of suppressed isotropic GWB signal. In this talk, I will present models of modified post-inflationary cosmology in which this tradeoff is made less severe. Such models significantly improve the detection prospects of these highly anisotropic GWBs at future GW experiments. |
||
| 17:00 to 17:15 | Rajesh Mondal (Indian Institute of Technology, Guwahati, India) |
Inflaton phenomenology via reheating in light of PGWs and the latest BICEP/Keck data Over the last decade, increasingly precise measurements of cosmic microwave background (CMB) have led to a new era of precision cosmology. Inflation is assumed to be a unique mechanism in the early universe, which, apart from solving the problems of the standard Big Bang, has very precise predictions of large-scale inhomogeneous fluctuations. During the course of subsequent evolution, those fluctuations are translated into CMB anisotropy. Therefore, accurate measurement of CMB anisotropy would be of fundamental importance for establishing the early inflationary phase. Two fundamental observables of interest are the scalar spectral index $n_s$ and tensor to scalar ratio $r$, which are directly connected to inflation. In our work, we have constrained the different inflationary models (like alpha-attractor model, minimal model) using the latest Plack-BICEP/KECK data. Primordial gravitational waves (PGWs) are one of the profound predictions of inflation. We consider high-frequency PGWs to obtain further constraints on the inflation model. Further, we also constrained the reheating parameters called reheating temperature and inflaton coupling. |
||
| 17:15 to 17:30 | Ayan Chakraborty (Indian Institute of Technology, Guwahati, India) |
Probing non-minimal coupling through super-horizon instability and secondary gravitational waves we investigate the impact of scalar fluctuations ($\chi$) non-minimally coupled to gravity, $\xi\chi^2 R$, as a potential source of secondary gravitational waves (SGWs). |
||
| 17:30 to 17:45 | Mainak Baidya (IISER Kolkata, India) |
Complementary signatures of α−attractor inflation in CMB and cosmic string Gravitational Waves When cosmic strings are formed during inflation, they regrow to reach a scaling regime, leaving distinct imprints on the stochastic gravitational wave background (SGWB). Such signatures, associated with specific primordial features, could be detectable by upcoming gravitational wave observatories like LISA, Einstein Telescope (ET), and others. Our analysis explores scenarios where cosmic strings form either before or during inflation. We examine how the number of e-folds experienced by the cosmic strings during inflation correlates with the predictions of inflationary models observable in CMB measurements. This correlation provides a testable link between inflationary physics and associated gravitational wave signals in a complementary manner. Focusing on α-attractor models of inflation,with the Polynomial α-attractor serving as an illustrative example, we find constraints, for instance, on the spectral index ns to 0.962 ≲ ns ≲ 0.972 for n = 1, 0.956 ≲ ns ≲ 0.968 for n = 2, 0.954 ≲ ns ≲ 0.965 for n = 3 and 0.963 ≲ ns ≲ 0.964 for n = 4 which along with the GW signals from LISA are capable of detecting local cosmic strings that have suffered ∼ 34 − 47 e-folds of inflation consistent with current Planck data and also testable in the upcoming CMB experiments like LiteBIRD and CMB-S4. |
||
| 17:45 to 18:00 | Nimmala Narendra (Indian Association for the Cultivation of Science, Kolkata, India) |
Gravitational waves from the first-order phase transition as a probe of high scale Leptogenesis We study the impact of Leptogenesis on Gravitational Waves from phase transition. We consider a heavy scalar field that decays into radiation and heavy right-handed neutrinos. These heavy right-handed neutrinos decay eventually and generate the lepton asymmetry. A part of the lepton asymmetry transfers into the baryon asymmetry of the Universe via the sphaleron transitions. We identify the parameter space of Leptogenesis where it maybe probed due to the Gravitational Wave spectral shapes. We show that a Gravitational Wave signal which can be detectable in the low-frequency range of future predictions of LISA that is consistent with Leptogenesis. |