Conveners
Cosmology
- ZACHARY PICKER
Cosmology
- Jan Hamann (The University of New South Wales)
Cosmology
- Jia Liu (IPMU)
We analytically calculate the spectrum of stochastic gravitational waves (GWs) emitted by expanding string loops on domain walls in the scenario where domain walls decay by nucleation of string loops. By introducing macroscopic parameters characterizing the nucleation of the loops, the stochastic GW spectrum is derived in a way that is independent of the details of particle physics models. In...
We study gravitational wave (GW) signatures from dark sector phase transitions as an explanation of the stochastic GW signal in the nHz range reported by the NANOGrav, Parkes and European Pulsar Timing Array (PTA) experiments. In contrast to earlier works, which have focused on fitting the PTA results with phenomenological phase transition parameters, we perform a detailed analysis of the GW...
Several Pulsar Timing Array (PTA) collaboratiosn have recently announced strong evidence for a stochastic gravitational background (SGWB) at nanohertz frequencies. In the same frequency range, high precision astrometry with surveys like Gaia can offer complimentary constraints on SGWB by tracking the positions of a large number of distant sources. We review the astrometric response to SGWB...
The question that what constitutes Dark Matter (DM) is one of the most pressing ones in contemporary physics, and one that has not been answered to any degree so far. Primordial Black Holes (PBHs) are one of the most well-motivated dark matter candidates. PBHs which are light enough that the Hawking radiation is substantial have been constrained by either the non-detection of the radiation...
Post-recombination cosmological probes offer some of the most stringent constraints on the properties of Dark Matter. The Cosmic Microwave Background (CMB), within the ΛCDM framework, has provided precise measurements of the Dark Matter density and its properties. Similarly, with upcoming 21cm experiments, the 21cm signal is a promising late-time cosmological probe, particularly sensitive to...
Several unified models that embed the SM elegantly have the possibility of domain wall formation according to Kibble mechanism. In models based on supersymmetric and non-supersymmetric left-right symmetric models, we discuss the emergence of such walls in the early universe and their signature in gravitational waves and the links to leptogenesis and EDM searches.
References...
Metastable cosmic strings are gathering attention as potential progenitors of stochastic gravitational wave background. They result from a two-step symmetry breaking $G\to H\to 1$ with $\pi_1(G)=0$ and $\pi_1(H)\ne 0$, and decay via internal monopole-antimonopole pair creation.
Conventionally, the breaking rate has been estimated by an infinitely thin string approximation, which requires a...
One of the exciting mysteries uncovered by the James Webb Space Telescope is the discovery of very high redshift supermassive black holes (SMBH). Such early formation of SMBH challenges conventional formation mechanisms---one possible explanation is that these black holes formed from the direct collapse of massive dust clouds. However, it has long been understood that the onset of cooling from...
Long-lived configurations of massive scalar fields around black holes may form if the coupling between the mass of the scalar field and the mass of the black hole is very small. In this work, we analyse the effect of self-interaction in the distribution of the long-lived cloud surrounding a stationary black hole. We consider both attractive and repulsive self-interactions.
From the perspective of Particle Physics, Dark Energy is a low energy phenomenon. Thus, our expectation is that field theory in curved space time should be sufficient to understand the physics of Dark Energy. However, in the context of the Standard Model of Particle Physics obtaining fields with sufficiently low masses that can be protected technically and be relevant for Dark Energy physics...
We propose a novel and comprehensive particle physics framework that addresses multiple cosmological tensions observed in recent measurements of the Hubble parameter, $S_8$, and Lyman-$\alpha$ forest data. Our model, termed `{\bf SIDR$+{z_t}$}' (Self Interacting Dark Radiation with transition redshift), is based on an inelastic dark matter (IDM) scenario coupled with dark radiation, governed...
