I discuss how the origin of neutrino mass and baryon asymmetry may lead to gravitational wave signal from cosmic strings. In some cases of symmetry breaking patterns from GUT, cosmic strings may come with magnetic monopoles or domain walls, making the gravitational wave spectrum richer. We may learn how the GUT is broken if the gravitational wave signal can be mapped out for a wide range of...
In this talk we will review the different ingredients that go into the
calculation of the stochastic gravitational wave background from cosmic strings and explain how one can extract the relevant information by performing large scale cosmological simulations of Nambu-Goto strings. Finally, we will also discuss
how current efforts to take into account gravitational backreaction can impact on...
The nonlinear memory effect is a fascinating prediction of general relativity (GR), in which oscillatory gravitational-wave (GW) signals are generically accompanied by a monotonically-increasing strain which persists in the detector long after the signal has passed. This effect is directly accessible to GW observatories, and presents a unique opportunity to test GR in the dynamical and...
In this talk I will discuss two important aspects of cosmology and particle physics that can be probed with GW signals from cosmic strings: probing the pre-BBN primordial dark age and axion physics. Gravitational waves (GWs) originating from the dynamics of a cosmic string network have the ability to probe many otherwise inaccessible properties of the early universe. In particular, I will...
We present new results on the gravitational wave signal from kinetic turbulence in the aftermath of a first order phase transition in the early universe
In this talk, I discuss work where we calculate the velocity of the Higgs condensate bubble wall during a first-order electroweak phase transition in the early Universe. The interaction of particles with the bubble wall can be accompanied by the emission of multiple soft gauge bosons. When computed at fixed order in perturbation theory, this process exhibits large logarithmic enhancements...
In first-order cosmological phase transitions, the asymptotic velocity of expanding bubbles is of crucial relevance for predicting observables like the spectrum of stochastic gravitational waves, or for establishing the viability of mechanisms explaining fundamental properties of the universe such as the observed baryon asymmetry. In these dynamic phase transitions, it is generally accepted...
A first-order phase transition in the early universe would have given rise to a stochastic gravitational wave background which may be observable today. In this talk, I will focus on the crucial problem of making reliable predictions in the face of infrared Bose enhancements at high temperature. Such enhancements break the alignment between the loop and coupling expansions, and typically lead...
In many extensions of the Standard Model, the electroweak transition is first order - in some cases, strongly so. The ensuing phase transition would result in collisions of bubbles of the new Higgs phase. These collisions, and the associated interactions of sound waves in the plasma, are substantial sources of gravitational waves. For a phase transition at or around the electroweak scale,...
We will discuss energy budget of first order phase transitions and identify models capable of supporting extreme supercooling necessary to feature bubble collisions as the main source of gravitational waves. We will also review new semi-analytical calculation of the spectrum appropriate in such strong transitions.
Cosmological first-order phase transitions are predicted by many new physics models and could have facilitated the generation of the baryon asymmetry. Gravitational waves are a promising tool to study phase transitions in the early universe. In this talk, I focus on the energy budget of such phase transitions, which is an important factor in the prediction of the gravitational wave spectrum....
I will review the current status of inflation and discuss how
one can improve it using new observational probes.
New interactions of neutrinos with a subdominant component of dark matter can prevent them from free streaming. As a result, the inflationary gravitational waves escape the damping by neutrinos and, with respect to the standard LCDM cosmology, there is enhancement of primordial gravitational wave amplitude and CMB B-modes on small scales. The effect on the CMB scalar acoustic oscillations is...
The dynamics of axions after inflation can give rise to an observable stochastic gravitational wave background. I will present new results for the GW spectrum from a lattice simulation of an axion-dark photon system in a radiation dominated universe, and furthermore show that this signal could explain the recently observed excess in the NANOGrav data.
Gravity and matter are universally coupled, and this unique universality provides us with an intriguing way to quantifying quantum aspects of space-time in terms of the number of gravitons. In particular, I will provide a limit on the number of gravitons if we trace out the matter degrees of freedom. I will obtain the universal bound on the number of gravitons. Since the number of gravitons...
Inflation is an epoch in the very early universe, characterised by a nearly exponential expansion. It provides an explanation for the origin of cosmic structure and it is in excellent agreement with current observations. The particle physics description of inflation is, however, still largely unknown. Primordial gravitational waves have the potential to shed new light on this epoch. In this...
Heavy particles can be produced on shell during inflation and leave distinct signals in the correlations of density fluctuations. These signals can be searched for in the future CMB/LSS/21cm observations. In this talk I will introduce the basics of this cosmological collider program. I will then describe some recent works along this direction with fun physics and visibly large signals,...
I will begin by reviewing the possibility that primordial black holes may make up the dark matter. I will then describe an array of analyses that can be done with CMB data and galaxy surveys to look for the effects of Hubble-scale gravitational waves and also to seek chirality in the gravitational-wave background.
We will review recent results about the search for a cosmological imprint of quantum gravity in gravitational-wave physics.Tight constraints and a chance of detection for some models may come from modified dispersion relations, the luminosity distance of standard sirens and the stochastic gravitational-wave background.
My talk will be composed of two parts. During the first part, I will be talking about formation of transmuted black holes via particle dark matter accumulation in compact stars. Stellar objects catastrophically accrete non-annihilating dark matter, and the small dark core subsequently collapses, eating up the host star and transmuting it into a black hole. The wide range of allowed dark...
Many gravitational theories beyond general relativity have been proposed over the years as a physical explanation of the dark sector. All such theories affect the emission, propagation and detection of gravitational waves. In this talk, I will discuss some proposed scenarios and how the GW170817/GRB170817A simultaneous detection of gravitational and electromagnetic waves from the same source...
The science case for a broad program of gravitational wave (GW) detection across all frequency bands is exceptionally strong. At present, there is a dearth of coverage by existing and proposed searches in the GW frequency band lying between the peak sensitivities of PTAs and LISA, roughly 0.1-100 microhertz. In this talk, I will outline a conceptual mission proposal to access this band. I will...
When a burst of neutrinos from a core collapse supernova passes by the Earth, it causes a permanent change in the local space-time metric, called the gravitational memory. Long considered unobservable, this effect will be detectable in the future, for a galactic supernova, at upcoming deci-Hertz gravitational wave interferometers. I present a new phenomenological description of the memory and...
Low-frequency gravitational waves cannot be detected with ground-based detectors.
While GW observations at frequencies in the micro- to mHz regime are planned with
spaced-based detectors, even lower frequencies, such as at nHz frequencies, can be
detected with pulsar timing arrays (PTAs). The talk summarises the PTA experiments,
describes the current status and prospects, and also...
Advanced LIGO and Virgo have detected dozens of gravitational waves, emitted from binary neutron stars and binary black holes. Third-generation observatories - such as Cosmic Explorer and the Einstein Telescope - will provide a significant boost in sensitivity and detect thousands of binary mergers per month, both from the local universe and from cosmological distances. In this talk I will...
Observations of the temperature anisotropies of the cosmic microwave background radiation have been key to our understanding of the early universe. The cosmic microwave background also contains invaluable information about the early universe that can be revealed through precision observations of the polarization anisotropies. Perhaps most strikingly, measurements of the polarization...
