Boundary correlators of dS bulk fields are important theoretical data for QFT in dS, and are also observables of cosmological collider physics. We will present recent progress in understanding the analytic structure of these inflation correlators with massive exchanges at either tree or loop orders. We will explain why the nonanalyticity of Inflation Correlators is phenomenologically...
I will talk about dark matter in the eV mass range.
The topic includes experimental hints, dark matter theory, and future experimental prospects.
We extend the Standard Model quantum chromodynamics theory (QCD) theory and naturally realize a first-order phase transition at high temperatures above 1 GeV without running into current constraints from both heavy ion colliders and early cosmology. This phase transition is from a non-perturbative effect of the QCD and can have a great impact on the early universe, including gravitational wave...
We propose a UV completion model for pseudo-Nambu-Goldstone dark matter with a hidden U(1) gauge symmetry. Dark matter scattering off nucleons is highly suppressed by the UV scale and direct detection constraints can be easily evaded. The kinetic mixing between the hidden U(1) and the $\mathrm{U(1)_Y}$ gauge fields would lead to dark matter decays. The current bound on the dark matter lifetime...
In the present work, the connection between the smallness of the neutrino masses and the stability of the proton is studied. We analyze this connection from different perspectives: the smallness of neutrino mass and the proton stability originate from the same source, small neutrino masses lead to a long lived proton, and the smallness of the proton decay width as a cause of the naturally...
Dark matter (DM) constitutes 26.8% of the entire universe and is one of the most significant mysteries in modern physics. The study of its particle properties is a critical and forefront topic in particle physics and cosmology, unlocking a deeper understanding of the universe and establishing the inherent unity of science.Ultralight dark matter could address small-scale structure problems of...
High-frequency gravitational waves (HFGWs) carry a wealth of information on the early Universe with a tiny comoving horizon and astronomical objects of small scale but with dense energy. We demonstrate that the nearby planets, such as Earth and Jupiter, can be utilized as a laboratory for detecting the HFGWs. These GWs are then expected to convert to signal photons in the planetary...
Understanding the nature of dark matter and the first luminous objects of the universe is an indomitable urge of human beings. Various 21 cm signals from neutral hydrogen and various experiments have been proposed, or being used, to unveil the mysteries, but suffering from parameter degeneracies between particle physics and the unknown astrophysics at cosmic dawn. The 21-cm absorption lines...
We consider a two-step freeze-in mechanism of a singlet fermionic dark matter (DM) $\chi$ in a gauged $U(1)_{B-3L_i}$, $i \in \{e,\mu,\tau\}$, extension of the Standard model (SM). The DM communicates with the SM only through flavorful vector-portal $Z_{B3L}$ due to its non-trivial charge $x$ under $U(1)_{B-3L_i}$, which also guarantees the stability of the DM over the age of the Universe for...
Ultralight particles are well-motivated in many physical theories beyond Standard Model of particle physics. They can also be Dark Matter candidates. If these ultralight fields couple to standard model particles, they would show as additional signals with characteristic features. We show future space-based gravitational-wave interferometry can serve as a sensitive method to detect these light...
We will explore the possibility that the nano-Hz stochastic gravitational wave background recently reported by several Pulsar Timing Arrays is due to a first-order phase transition of a nearly conformal dark sector, using the dual radion effective potential formalism. The dark radiation from the secluded dark sector can alleviate the Hubble tension without violating the $\Delta N_{\rm eff}$...
The exotic Z decays to a QCD-like dark sector provide unexplored opportunities at colliders. In this talk, we explore the region where the Z portal is generated by a dark Z′. The phenomenological signatures of light Z' are studied, with both dark shower signals in Z decays and rare decays of B hadrons taken into account.
The often-considered dark matter (DM) candidates, e.g., WIMP and ALP, are in tension with observations, which motivates new proposals for DM. The recently proposed féeton dark matter, a B-L gauge boson with a small mass and feeble coupling to the standard sector, constitutes a well-motivated dark matter model consistent with cosmology, Seesaw mechanism, and leptogenesis. This model predicts...
Cosmic strings are line-like topological defects which can be formed in the early universe. In this talk, I first review basic concepts and general features of cosmic strings. Then I will explain how to evaluate interaction energies of two cosmic strings, and discuss our recent results. I also discuss phenomenological implications of our results such as the formation of the bound state of...
