We compute the causality/positivity bounds on the Wilson coefficients of scalar-tensor effective field theories. Two-sided bounds are obtained by extracting IR information from UV physics via dispersion relations of scattering amplitudes, making use of the full crossing symmetry. The graviton t-channel pole is carefully treated in the numerical optimization, taking into account the constraints...
Lattice simulation of QCD at small net baryon densities and high temperature have revealed that the transition to hadronic phase to the deconfined quark-gluon plasma is a crossover. Recently, the structure of neutron stars have been studied with a crossover equation of state by means of a switching function to model a smooth transition from a pure neutron matter to massless quarks. The switch...
The nature of dark energy is one of the most pressing open questions in physics. While the standard ΛCDM model assumes a static cosmological constant, alternative approaches suggest a dynamical scalar field as the source of cosmic acceleration. In this work, we propose a shockwave-driven model, where dark energy emerges as a high-energy vacuum excitation of a gravitationally coupled scalar...
A method of general applicability has been developed, whereby the null geodesic equations of the Einstein-Straus-de Sitter metric can be integrated simultaneously in terms of the curvature constant k. The purpose is to generalize the computation of light deflection and time delay by a spherical mass distribution. Assuming a flat Universe with most recent measurements of the Hubble constant H₀...
Domain walls are a type of topological defect that can arise in the early universe after the spontaneous breaking of a discrete symmetry. This occurs in several beyond Standard Model theories with an extended Higgs sector, such as the Next-to-Two-Higgs-Doublet model (N2HDM). In this talk, I will discuss the domain wall solution related to the singlet scalar of the N2HDM as well as demonstrate...
Gravitational and Structural Modifications of Compact Objects due to Quadrupole Moments in General Relativity
This study investigates the gravitational behavior of compact astrophysical objects, specifically white dwarfs and neutron stars, within Einstein’s General Relativity framework. We incorporate the quadrupole moment in a first-order approximation to analyze how deviations from...
X-ray polarimetry is an observational technique with the potential to enrich our understanding of high-energy astrophysics by enabling the measurement of the polarization of X-rays emitted by exotic cosmic phenomena such as black holes, neutron stars, Gamma-Ray Bursts and more. This technique provides crucial insights into the magnetic field geometries, intensities, and emission mechanisms of...