Workshop on Very Light Dark Matter 2021

Session

Wednesday PM

Sep 29, 2021, 2:00 PM

Online

Conveners

Wednesday PM

• Ippei Obata

35. Revisiting the core-halo structure of Fuzzy Dark Matter Halo

Hei Yin Jowett Chan

9/29/21, 2:00 PM

In simulations of Fuzzy Dark Matter (FDM) model, we always found gravitationally collapsed object composed of a solitonic core locating within a virialized halo. Although a measured relation between the core and halo mass, from simulation, is often adopted to make observational constraints on the particle mass, there is still a disagreement on the relation between different groups. To fully...

36. DMRadio: Searching for Axion Dark Matter Below 1 ueV

Jonathan Ouellet

9/29/21, 2:25 PM

The particle nature of Dark Matter (DM) is one of the most important open questions in particle physics today. Axions, and axion like particles (ALPs), more generally, have emerged as one of the leading candidates to to explain the DM abundance of the universe. Experimental searches for axion DM (aDM) have traditionally searched in a narrow mass band between 1~100 ueV using microwave cavity...

37. Cosmic birefringence and its implications for axion phenomenology

Silvia Gasparotto

9/29/21, 2:50 PM

Invited

A recent measurement of the non-zero isotropic birefringence angle with a 2.4 sigma level in Planck 2018 polarization data opens a tantalizing window for testing the parity-violating extension of the Standard Model. In this talk, I will explain the measurement of cosmic birefringence and discuss its implications for dark matter and dark energy models in the context of axion physics.

39. Axion Dark Matter in the Time of Primordial Black Holes

Yong Xu

9/29/21, 4:05 PM

In this talk, we present the phenomenology of QCD axion dark matter in a nonstandard cosmological era triggered by PBHs that fully evaporate before the onset of BBN. We show that PBHs have a strong impact on the dark matter produced via the misalignment mechanism. First, the oscillation temperature of axions reduces if there is a PBH dominated era, and second, PBH evaporation injects entropy,...

41. PyUltraLight 2: Simulating Interactions Between Ultra-Light Dark Matter and Massive Particles

Yourong Wang

9/29/21, 4:20 PM

I will discuss simulations a massive objects interacting with ULDM, using an extension of the PyUltraLight code. Simulations of a point mass moving in a uniform background and a SMBH moving within a ULDM soliton broadly confirm simple estimates of dynamical friction timescales. However, in addition to generating complex inhomogeneities, SMHB-ULDM interactions excite coherent ``breathing...

40. Search for DM self-annihilation to neutrino production in KamLAND

Kazumi Hata

9/29/21, 4:35 PM

KamLAND is an ultra-low BG detector with 1000 tons of liquid scintillator.

Taking advantage of this characteristic, we have made great achievements in the neutrino detection, and it can be fully utilized for dark matter search.

In this talk, the result of searching MeV-scale DM self-annihilation to neutrino production in KamLAND. No significant excess was found over the background...

45. Cosmic Birefringence Triggered by Dark Matter Domination

Shota Nakagawa

9/29/21, 4:50 PM

Recently, the Planck 2018 polarization data of cosmic microwave background (CMB) radiation suggested the non-zero rotation angle of CMB polarization plane, which is called cosmic birefringence. Cosmic birefringence is predicted if an axion-like particle (ALP) moves after the recombination. We show that this naturally happens if the ALP is coupled to the dark matter density because it then...

34. On the quantum origin of a small positive cosmological constant

Saurya Das

9/29/21, 5:05 PM

We show that Dark Matter consisting of ultralight bosons in a Bose-Einstein condensate induces, via its quantum potential, a small positive cosmological constant which is close to the observed value. This explains why the densities of Dark Matter and Dark Energy are approximately equal.

38. A Catalogue of Hadronic Axion Models

Sebastian Hoof

I will report on or recent results on creating catalogues of hadronic, aka KSVZ, axion models. In particular, when phenomenological selection criteria are taken into account, we find a finite number of possible anomaly ratios E/N, and hence a finite number of hadronic axion models at any given mass. The number of different E/N values is between 12 and 820, depending on the amount of freedom...