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Displaying 29 contributions out of 29
Presented by Prof. John ELLIS on 2 Dec 2022 at 18:30
In the first part, I will present the most recent constraints on cosmic strings using the O3 LIGO/Virgo/KAGRA data. I will then briefly discuss gravitational memory and its consequences for the obtained constraints on the string tension. In the second part, I will address the question whether the LIGO/Virgo detected GWs from binary back hole coalescences are of PBH instead of astrophysical origin ... More
Presented by Dr. Mairi SAKELLARIADOU
Heavy particles can be produced on shell during inflation and leave distinct signals in the correlations of density fluctuations. These so-called cosmological collider signals can be searched for in the future CMB/LSS/21cm observations. In this talk I will introduce the basics of the cosmological collider program. I will then talk about our current understanding of the signal structure and the und ... More
Presented by Zhong-zhi XIANYU on 1 Dec 2022 at 15:30
Phase transitions can have a dramatic impact on physics in the early universe. We illustrate this by discussing novel mechanisms of dark matter production, baryogenesis and primordial black hole production which hinge on cosmological phase transitions.
Presented by Michael BAKER on 29 Nov 2022 at 15:30
Presented by David DUNSKY on 28 Nov 2022 at 17:00
Presented by Alexander VIKMAN on 28 Nov 2022 at 16:00
Domain wall (DW) networks are interesting probes of new physics. They arise from the spontaneous breaking of any discrete symmetry and they have a strong impact on cosmology, producing loud gravitational wave (GW) signals and even primordial black holes. An important example of new physics leading to a long DW epoch is given by a class of well-motivated axion models. I will discuss their GW phenom ... More
Presented by Oriol PUJOLAS on 28 Nov 2022 at 15:30
We study the gravitational radiation emission efficiency Γ of superconducting cosmic strings. We demonstrate, by using a solvable model of transonic strings, that the presence of a current leads to a suppression of the gravitational emission of cusps, kinks and different types of loops. We also show that, when a current is present, the spectrum of emission of loops with cusps is exponentially sup ... More
Presented by Dr. Lara SOUSA on 28 Nov 2022 at 17:30
Presented by Volodymyr TAKHISTOV on 2 Dec 2022 at 14:30
The symmetry breaking of grand unified gauge groups in the early universe often leaves behind relic topological defects such as cosmic strings, domain walls, or monopoles. For some symmetry breaking chains, hybrid defects can form where cosmic strings attach to domain walls or monopoles attach to strings. In general, such hybrid defects are unstable and can leave behind unique gravitational wave f ... More
Presented by David DUNSKY
In this talk, we will discuss a novel source of gravitational waves from first order phase transitions beyond the ones conventionally studied in the literature (scalar field and sound waves): feebly interacting particles. If such particles carry a significant fraction of the energy released in the transition, they can generate gravitational wave signals that have qualitatively distinct characteris ... More
Presented by Bibhushan SHAKYA on 29 Nov 2022 at 17:30
Gravitational waves have offered us a whole new way of looking at our Universe. So far, we have seen them in the ~10-100 Hz range, and there are hints that we might soon see them in the nanohertz regime. However, there are parts of the frequency space that are currently not covered by any future or planned observations. I will explain how we can use upcoming photometric surveys to bridge the gaps ... More
Presented by Kris PARDO on 2 Dec 2022 at 16:30
We demonstrate analytically and numerically that "optimized partial dressing" (OPD) thermal mass resummation, which uses gap equation solutions inserted into the tadpole, efficiently tames finite temperature perturbation theory calculations of the effective thermal potential, without necessitating use of the high-temperature approximation. An analytical estimate of the scale dependence for OPD res ... More
Presented by Graham WHITE on 29 Nov 2022 at 16:00
In this talk, I will talk about two topics on GWs induced by scalar perturbations. One is about the enhancement of induced GWs with a sudden reheating, named the “Poltergeist mechanism”. When the universe experiences an early matter-dominated era that ends with a sudden reheating, the induced GWs are much enhanced due to fast oscillations of the scalar perturbations after the reheating. I wi ... More
Presented by Keisuke INOMATA on 1 Dec 2022 at 16:00
In this talk, we discuss gravitation wave signals not from inflation itself, but from models that are built using inflationary ideas. In particular, a post-inflationary epoch of evolving scalar VEV(s) can generate the observed baryon asymmetry through the Affleck-Dine mechanism. As this involves high scale physics, it is difficult to test experimentally, but we argue that the poltergeist mechan ... More
Presented by Lauren PAERCE on 1 Dec 2022 at 17:30
We will introduce CosmoLattice, a modern code for simulating the non-linear dynamics of interactive fields in an expanding background. As an application we will solve two different problems of inflationary cosmology: i) the non-linear dynamics of axion-inflation, ii) the use of gravitational waves from preheating as a probe of particle interactions
Presented by Daniel FIGUEROA on 1 Dec 2022 at 14:30
I will discuss a recently proposed class of models where Dark Matter (DM) is produced via an inverse phase transition. The inverse phase transition can be caused by coupling to some cosmological field. For instance, this field can be a primordial magnetic field, as in e-Print: 2010.03383 or thermal fluctuations of other fields, as in e-Print: 2104.13722. In the latter work DM is modelled as a real ... More
Presented by Alexander VIKMAN
Presented by Prof. Jonathan ELLIS on 28 Nov 2022 at 14:15
Presented by Prof. Laura SAGUNSKI on 2 Dec 2022 at 17:30
Presented by Joachim KOPP on 29 Nov 2022 at 18:00
Presented by Dr. Marek LEWICKI on 28 Nov 2022 at 18:00
Presented by Prof. Ivonne ZAVALA on 1 Dec 2022 at 18:00
Gravitational waves are an important probe of physics beyond the Standard Model, especially in theories with a first order phase transitions in the early universe. I will review aspects of simulations and models of the generation of gravitational radiation, calculations of phase transition parameters, and prospects for their estimation at the future space-based gravitational wave detector LISA.
Presented by Mark HINDMARSH on 29 Nov 2022 at 14:30
The Peters formula, which tells how the coalescence time of a binary system emitting gravitational radiation is determined by the initial size and shape of the elliptic orbit, is often used in estimating the merger rate of primordial black holes and the gravitational wave background from the mergers. Valid as it is in some interesting scenarios, such as the analysis of the LIGO-Virgo events, the P ... More
Presented by Heling DENG on 2 Dec 2022 at 17:00
Gravitational waves (GWs) have the potential to probe the entirety of cosmological history due to their nearly perfect decoupling from the thermal bath and any intervening matter after emission. In this talk, we will review the basic physics of spectral distortions (SDs) of the cosmic microwave background (CMB), and highlight how they uniquely probe GWs over six decades in frequency, bridging the ... More
Presented by Subodh PATIL on 1 Dec 2022 at 17:00
I will discuss how specially designed SRF cavities can have enhanced sensitivity to axions and gravitational waves for frequencies below GHz. The projected sensitivity of a futuristic apparatus covers the QCD line over two decades of axion dark matter mass and new parameter space all the way down to the fuzzy dark matter limit. Additionally, the same concept with a different geometry has the poten ... More
Presented by Raffaele-Tito D'AGNOLO on 2 Dec 2022 at 15:00
The first seven years of direct gravitational wave detection have had a huge impact not only on astrophysics, but also on cosmology and fundamental physics. We’ll start by reviewing some ways cosmologically-motivated departures from GR can affect gravitational wave propagation. Then I’ll present some constraints from current data and forecasts for future detectors using these methods. In parti ... More
Presented by Tessa BAKER on 2 Dec 2022 at 15:30
When the universe was a fraction of nano-second old the electroweak phase transition (EWPT) took place in which elementary particles obtained masses via the Higgs mechanism. In extensions of the Standard Model this transition can be first order with possibly observable consequences. It would be great to have a simple and model-independent description of this process in terms of the Standard Model ... More
Presented by Marieke POSTMA on 29 Nov 2022 at 17:00
Presented by Mairi SAKELLARIADOU on 28 Nov 2022 at 14:30