Marco Gorghetto (Weizmann): “More Axions from Strings”
The axion solution to the strong CP problem also provides a natural dark matter candidate. If the Peccei-Quinn symmetry has ever been restored after inflation, topological defects of the axion field would have formed and produced relic axions, whose abundance is in principle calculable. We study the contribution to the abundance produced by string defects during the so-called scaling regime. … Read More
4D Seminar | Manibrata Sen (UC Berkeley) “Diffuse supernova background neutrinos: a possible contender for fundamental physics probes”
Abstract: The Universe is awash with tens-of-MeV neutrinos of all species coming from all past core-collapse supernovae, also known as the diffuse supernova neutrino background (DSNB). Detecting the DSNB would open up new avenues in multi-messenger astronomy. In particular, it offers the unique opportunity to probe properties of the cosmos using neutrinos, as opposed to photons. The Super-Kamiokande experiment, loaded with … Read More
4D Seminar | Zhengkang Kevin Zhang (Caltech) “Effective Field Theory of Dark Matter Direct Detection With Collective Excitations”
I will present a framework for computing dark matter direct detection rates via phonon and magnon excitations in crystal targets for general dark matter models. It consists of parameterizing dark matter interactions by a nonrelativistic EFT, and computing material responses to the EFT operators. Our work extends previous calculations that focused on simple models such as standard spin-independent interactions, and … Read More
4D Seminar | Tom Rudelius (UC Berkeley) “Generalized Global Symmetries and the Swampland”
Abstract: Standard lore holds that a consistent theory of quantum gravity cannot have exact global symmetries. In this talk, we will show how simple generalizations of this lore can be used to motivate a number of other well-supported “Swampland conjectures,” thereby highlighting the importance of global symmetries for understanding universal features of quantum gravity. We remark briefly on possible consequences … Read More
4D Seminar: Kyohei Mukaida (CERN) “Leptogenesis from axion inflation”
4D Seminar: Kyohei Mukaida (CERN) “Leptogenesis from Axion Inflation”Abstract: In inflation models driven by an axion-like particle, the inflaton may have a Chern-Simons coupling to the Standard Model (SM) U(1)_Y. During inflation, this Chern-Simons coupling sources dual production of B+L asymmetry and maximally helical U(1)_Y gauge fields, associated with the SM chiral anomaly equation. In this talk, we will show … Read More
Majid Ekhterachian (Maryland) “Cosmological phase transition of composite Higgs confinement and the fifth dimension”
Abstract: I will discuss the cosmological (de)confinement phase transition (PT) of nearly conformal, strongly coupled large N field theories, applicable to composite Higgs models, using their holographic dual 5D formulation. In this description, the PT is from the high temperature phase in which the IR of the warped extra dimension is covered by a black-brane horizon to the low temperature … Read More
4D Seminar | Josh Foster (UMich) “Astrophysical Searches for Axions”
The QCD axion, which may solve the Strong CP problem, and axion-like particles, which arise naturally in many models of high-scale physics, provide theoretically compelling dark-matter and dark-sector candidates. The extreme environments characterized by large magnetic fields, high densities, and high temperatures realized in astrophysical contexts provide natural laboratories to search for axions which couple to electromagnetism and matter. In … Read More
4D Seminar | Michael Wilson (Berkeley Center for Cosmological Physics) “Current & future large-scale structure constraints on Dark Energy & Inflation”
Abstract: DESI will measure the 3D position of 30 million galaxies during the next five years to precisely characterize the nature of Dark Energy with baryon acoustic oscillations & redshift-space distortions. Unique signatures present in the large-scale distribution ofgalaxies further limit the level of non-Gaussian fluctuations present in the early Universeand the mechanism of Inflation by extension. I will introduce the DESI experiment, summarise … Read More
4D Seminar | Simone Ferraro (LBNL) “Fundamental physics from the next generation of CMB and Large Scale Structure experiments: prospects and challenges”
Abstract: I will discuss how the next generation of CMB and Large Scale Structure (LSS) experiments can uncover information about the primordial Universe. I will review the observational signatures of the initial conditions and explain how they are connected to the physics of Inflation. I will then highlight recent techniques that combine CMB and LSS measurements to probe velocity fields … Read More
4D Seminar | Azadeh Maleknejad (CERN) “A new paradigm for particle cosmology”
Azadeh Maleknejad (CERN) “A new paradigm for particle cosmology” Abstract: Modern cosmology has been remarkably successful in describing the Universe from a second after the Big Bang until today. However, its physics before that time is still much less certain. It profoundly involves particle theory beyond the Standard Model to explain long-standing puzzles: the origin of the observed matter asymmetry, … Read More