Gravitational Wave Probes of Physics Beyond Standard Model 4

Contribution List

10. "Theoretical and Observational Bound on Scalar fields In Modified Symmetric Teleparallel Gravity"

In this presentation, I will provide an overview of our recent research contributions in the context of scalar field cosmology within the framework of symmetric teleparallel gravity. Specifically, I will discuss the findings from our three published papers, along with two additional manuscripts that are currently under review.

A significant portion of our work focuses on the...

2. Black holes and gravitational waves from phase transitions in realistic models

Among all the possible candidates for Dark Matter, one appealing example is a population of Primordial Black Holes, which could have been borne by various processes in the early stages of the Universe. In this talk, I will investigate the formation of such objects as the result of the collapse of energy density fluctuations originating from supercooled first-order phase transitions. I will...

7. Bubble Nucleation and Gravitational Waves from Strongly Coupled QFT's.

Gravitational waves (GWs) produced during first-order phase transitions (FOPTs) in strongly coupled quantum field theories (QFTs) pose a significant challenge for precise prediction due to the complexities of strong coupling. In this talk, we present a method for predicting the GW spectra of such theories by integrating holographic techniques with lattice data from pure SU(N) Yang-Mills...

21. Bubble wall dynamics from non equilibrium quantum field theory

Gravitational waves (GWs) produced during a first-order phase transition are a favourite candidate as a probe of beyond the standard model physics at future space-based experiments. The spectrum of produced GWs depends strongly on the terminal velocity at which bubbles of the broken phase expand in the plasma, and in particular on whether this velocity can become ultrarelativistic.
In this...

1. Bubble wall velocity from hydrodynamics

Terminal velocity reached by bubble walls in cosmological first-order phase transitions is an important parameter determining both primordial gravitational wave spectrum and the production of baryon asymmetry in models of electroweak baryogenesis. In this talk I discuss the recent results for local thermal equilibrium approximation for which, using hydrodynamic simulations, we have confirmed...

20. C-parity, magnetic monopoles and higher frequency gravitational waves

We will discuss the complementary signatures of gravitational waves and observable flux of the GUT monopoles when $SO(10)$ grand unified symmetry is spontaneously broken via the left-right symmetric model with C-parity also unbroken [$C$ converts $Q\to -Q$, where $Q$ is the electric charge operator in $SO(10)$.] This breaking produces the topologically stable GUT monopole as well as a GUT...

22. Dynamical nonlinear tails in black hole ringdown

Nonlinear tails in black hole perturbations, arising from second-order effects, present a distinct departure from the well-known Price tail of linear theory. We present an analytical derivation of the power law indices and amplitudes for nonlinear tails stemming from outgoing sources, and validate these predictions to percent-level accuracy with numerical simulations. We then perform a...

9. Gravitational Waves from a First-Order Phase Transition of the Inflaton

We explore the production of gravitational waves resulting from a first-order phase transition (FOPT) in a non-minimally coupled "Dark Higgs Inflation" model. Utilizing a single scalar field both as the inflaton and as the Dark Higgs breaking the gauge symmetry in the dark sector, we demonstrate the feasibility of a unified framework for inflation and observable gravitational waves from a FOPT.

12. Gravitational Waves from a Higgs-like spectator field

We study stochastic gravitational waves (GW) sourced by a Higgs-like spectator field via the modulated reheating mechanism. The curvature perturbations generated by the spectator in de Sitter vacuum are blue-tilted and strongly non-Gaussian. They must be suppressed on scales probed by the CMB anisotropies but can grow large on sub-Mpc scales, generating observationally testable stochastic GWs....

8. Gravitational waves from preheating in α-attractors

In multi-field inflationary models, couplings between fields are not limited to the potential of the model, but can also be present in kinetic terms. In such a case, they can be interpreted as a non-trivial structure of the space of fields. Non-vanishing curvature of this space can lead, if negative, to a new phenomenon called geometrical destabilization.

α-attractors are a very promising...

19. Gravitational waves from supermassive black holes at pulsar timing arrays

Inspiralling SMBH binaries constitute a natural explanation of the gravitational wave (GW) background discovered in pulsar timing array (PTA) data. In this talk, I will present a fast semianalytical computation of the expected GW background from SMBH binaries and discuss the SMBH fit to the PTA data that shows evidence of environmental effects or binary eccentricities. I will identify...

24. Memory Burden effects mimic the reheating signatures on SGWB from ultra low mass PBHs

Ultra-low mass primordial black holes (PBH), briefly dominating the expansion of the universe, would leave detectable imprints in the secondary stochastic gravitational wave background (SGWB). Such a scenario leads to a characteristic doubly peaked spectrum of SGWB and strongly depends on the Hawking evaporation of such light PBHs. However, these observable signatures are significantly altered...

15. Microlensing effect in the long-duration gravitational wave signals originating from Galactic sources

Detection of quasi-monochromatic, long-duration (continuous) gravitational wave radiation emitted by, e.g., asymmetric rotating neutron stars, planetary or asteroid mass - primordial BH (PBH) binaries during their in-spiral phase in our Galaxy requires a long observation time to distinguish it from the detector’s noise. If this signal is additionally microlensed by a lensing object located in...

16. Paths Through the Dark: Comparing Approaches to Cosmological FOPTs

We explore the dynamics of cosmological phase transitions in a dark sector model featuring a dark photon associated with a U(1)D gauge symmetry. Our analysis focuses on two complementary approaches to construct the effective potential: an  scale invariant model with the Coleman-Weinberg potential, both using the high-temperature approximation and a full numerical evaluation of the thermal...

14. Pre-thermalized Gravitational Waves

We investigate a novel gravitational wave (GW) production mechanism from gravitons generated during the pre-thermal phase of cosmic reheating, where the energy density is dominated by non-thermalized inflaton decay products, dubbed reheatons. We consider multiple production channels, including: $i)$ pure inflaton-inflaton annihilation, $ii)$ graviton Bremsstrahlung from inflaton decay, $iii)$...

4. Primordial Gravitational Waves from Phase Transitions during Reheating

We study primordial gravitational waves (GWs) generated from first-order phase transitions (PTs) during cosmic reheating. Using a minimal particle physics model, with a general parametrization of the inflation energy density and the evolution of the Standard Model temperature, we explore the conditions under which PTs occur and determine the corresponding PT parameters. We find that, in...

3. Primordial Graviton Production and Detection Prospects in the String Pre-Big Bang Scenario

We investigate the mechanism of primordial graviton production within the framework of string cosmology's pre-Big Bang scenario, focusing on the interpretation of the NANOGrav signal as a relic stochastic background of primordial gravitons.

Our analysis shows that the minimal version of the pre-Big Bang scenario encounters limitations in explaining the observed signal. However, generalized...

5. Probing leptogenesis with scalar induced gravitational waves

We demonstrate in this work that scalar-induced gravitational waves (SIGWs) can serve as a natural and powerful probe of thermal leptogenesis occurring at extremely high scales-beyond the reach of conventional particle physics experiments. As a proof of concept, we present a simple leptogenesis model in which an early matter-dominated phase, tracking the leptogenesis scale, is responsible for...

6. Probing SUSY at Gravitational Wave Observatories

Under the assumption that the recent pulsar timing array evidence for a stochastic gravitational wave (GW) background at nanohertz frequencies is generated by metastable cosmic strings, we analyze the potential of present and future GW observatories for probing the change of particle degrees of freedom caused, e.g., by a supersymmetric (SUSY) extension of the Standard Model (SM). We find that...

23. Prospecting a scalar Singlet-Triplet two component Dark Matter model with Gravitational Waves

We investigate gravitational wave (GW) production from a first-order electroweak phase transition (FOEWPT) in a two-component dark matter (DM) scenario. The Higgs sector of the Standard Model (SM) is extended by a complex scalar singlet and a hyperchargeless ($Y = 0$) scalar triplet. In this setup, the neutral component of the triplet serves as a DM candidate under a $\mathbb{Z}_2$ symmetry....

25. Pulsar Timing Array Evidence for Self–Interacting Dark Matter in Super-Massive Black-Hole Mergers

Pulsar timing arrays (PTAs) have now revealed a nano-hertz stochastic gravitational-wave background whose amplitude and spectral shape are consistent with a cosmic population of merging super-massive black-hole (SMBH) binaries. Explaining how such binaries bridge the ``final parsec’’ separation before gravitational radiation dominates remains a key challenge. Following the mechanism proposed...

18. Searches for Inflationary Gravitational Waves in the NANOGrav 15 yr data-set

In this talk, I will summarize some of our efforts to interpret the GWB-like signal observed by the NANOGrav collaboration as inflationary gravitational waves, by sampling reheating temperature, tensor spectral index, and the running of the tensor spectral index. I will show that there is available parameter space to describe the signal, even if we impose constraints from CMB, LVK, and do not...

11. Supercooled Audible Axions

We present the audible axion mechanism extended by a period of supercooling that delays the onset of axion oscillations. While the original setup relies on a large axion decay constant and coupling to a dark Abelian gauge field to produce sizable gravitational wave signals, in this talk we discuss how supercooling opens up the testable parameter space and reduces the required coupling to...

13. Supercooled Dark Scalar Phase Transitions explanation of NANOGrav data

The evidence of a Stochastic Gravitational Wave Background (SGWB) in the nHz frequency range is posed to open a new window on the Universe. A preferred explanation relies on a supercooled first order phase transition at the 100 MeV–GeV scale. We address address its feasibility going from the particle physics model to the production of the gravitational waves. We take a minimal approach for the...

17. Using graviational waves to look for dark matter (in)directly

Gravitational wave detectors offer promising probes to search for dark matter, both directly and indirectly. If dark matter originates from a background of ultralight gauge bosons, these bosons could exert forces on the test masses of gravitational wave detectors, inducing displacements with characteristic frequencies determined by the boson mass. On the indirect side, the Fermi satellite has...