Théorie

Stueckelberg massive electromagnetism in de Sitter and anti-de Sitter spacetimes: Two-point functions and renormalized stress-energy tensors

 We discuss Stueckelberg massive electromagnetism on an arbitrary four-dimensional curved spacetime. By considering Hadamard vacuum states, we construct the two-point functions associated with Stueckelberg massive electromagnetism in de Sitter and anti-de Sitter spacetimes. We present the Hadamard renormalization of the expectation value of the stress-energy-tensor operator, and we provide its explicit expression for the Stueckelberg theory.

Chiral electrodynamics in astrophysics and cosmology

An asymmetry between left- and right-chiral lepton states can induce

additional contributions to the electromagnetic current in the presence

of magnetic fields or vortical fluid flows. In contrast to the usual Ohmic

current these chiral currents are dissipationless. They can lead to instabilities

such as the chiral magnetic effect in which magnetic fields can undergo an

exponential growth phase, similar to the dynamo effect. We discuss astrophysical

and cosmological contexts in which such effects may play a role, such as

New Directions in Dark Matter Direct Detection

Sub-GeV dark matter is a theoretically motivated but largely unexplored paradigm of dark matter. In this talk, I will discuss recent work on the direct detection of sub-GeV dark matter through dark matter-electron scattering. I will present some motivated models that can be probed with these techniques as well as projections for current and near-term noble liquid, semiconductor, and scintillator experiments. Finally, I will discuss some new techniques that may allow us to more robustly discriminate between dark matter signatures and background.

Late time cosmology with LISA: probing the cosmic expansion with massive black hole binary mergers as standard sirens

I will summarize the potential of the LISA mission to constrain the expansion history of the universe using massive black hole binary mergers as gravitational wave standard sirens. After briefly reviewing the concept of standard siren, I will outline the analysis and methodologies to use LISA as a cosmological probe, and present estimates for the power of LISA in constraining cosmological parameters for both standard and alternative cosmological models.

Galactic sources: update information from gamma-rays experiments and implications for IceCube

Air-Cherenkov telescopes have mapped the Galactic plane at TeV
energies. Here we evaluate the prospects for detecting the neutrino
emission from sources in the Galactic plane assuming that the highest
energy photons originate from the decay of pions. Four promising
sources are identified based on having a large flux and a flat
spectrum. We subsequently evaluate the probability of their
identification above the atmospheric neutrino background in IceCube
data as a function of time. We show that observing them over the

Intricacies of the dark universe

Most of the matter in our universe is in the form of dark matter. The research of the past decades led to the development of two canonical paradigms for its properties: the collisionless cold dark matter paradigm, supported by the observed gravitational clustering, and the WIMP paradigm, which provides a well-motivated particle physics framework for collisionless cold dark matter. However, current observational and experimental results motivate looking beyond these scenarios.

Highly Excited Strings

Highly excited strings and their interactions are likely to play a fundamental role in string black hole physics, cosmic superstrings and associated string phenomenology such as gravitational wave detection.  I will discuss a novel and efficient approach to computing such observables directly from worldsheet string path integrals.

Recent results about vector- and multi-Galileon theories

   Galileon models follow the Horndeski systematic construction to couple additional fields to gravity in order to modify the Einstein equations. There were first investigated from 2009 in the case of a single scalar field. Thus, there have been an increasing interest in similar models involving either a vector field or several scalar or vector fields. During this talk, I will present results from these different topics.

Exotic RG flows from holography

The AdS/CFT correspondence, a useful tool in the study of strongly coupled physics, relates fields, including gravity, in a d+1 dimensional asymptotically AdS space-time to operators in a d-dimensional Conformal Field Theory (CFT), in a one-to-one correspondence. The extra spatial dimension appearing in the gravitational side of the duality, the holographic dimension, is in correspondence with an energy scale on the QFT side: fields evolving along the holographic dimension are dual to renormalization group flows of couplings to the dual QFT operators.

Helicity coherence in binary neutron star mergers and non-linear feedback

Neutrino flavor conversion studies based on astrophysical environments usually implement neutrino mixings, neutrino interactions with matter and neutrino self-interactions. In anisotropic media, the most general mean-field treatment includes neutrino mass contributions as well, that introduce a coupling between neutrinos and antineutrinos termed helicity or spin coherence. We discuss resonance conditions for helicity coherence for Majorana neutrinos. We explore the role of these mean-field contributions on flavor evolution in the context of a binary neutron star merger remnant.

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