A5028103105- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Particle physics theoretical and experimental studies
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Particle Detector Development and Performance
- Solar and Space Plasma Dynamics
- Astronomy and Astrophysical Research
- Geophysics and Gravity Measurements
- Radiation Detection and Scintillator Technologies
- CCD and CMOS Imaging Sensors
- Quantum Electrodynamics and Casimir Effect
- Advanced Thermodynamics and Statistical Mechanics
- Chemical Reactions and Isotopes
- Gamma-ray bursts and supernovae
- Black Holes and Theoretical Physics
- Nuclear Physics and Applications
- Space Science and Extraterrestrial Life
Johns Hopkins University
2020-2025
Stanford University
2024-2025
Sofia University
2024
École Polytechnique Fédérale de Lausanne
2019
Korea Advanced Institute of Science and Technology
2017
Institute for Basic Science
2017
Dark matter may exist today in the form of ultraheavy composite bound states. Collisions between such dark states can release intense bursts radiation that include <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>γ</a:mi></a:math>-rays among final products. Thus, indirect detection signals unconventional <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:mi>γ</c:mi></c:math>-ray bursts. Such have been missed not necessarily because their low...
From a model-building perspective, the inflationary sector might very well have no direct couplings to other species, apart from inevitable gravitational interactions. Within context of General Relativity, thermal universe can still emerge after inflation if: i) some radiation is excited towards end inflation, and ii) post-inflationary equation state becomes sufficiently stiff w ⩾ wRD≳ 0.57, with wRD threshold depending on scale H* initial radiation-to-inflaton energy ratio Δ*. Furthermore,...
The expansion history of the Universe between end inflation and onset radiation-domination (RD) is currently unknown. If equation state during this period stiffer than that radiation, w > 1/3, gravitational wave (GW) background from acquires a blue-tilt d log ρGW/ f = 2(w−1/3)/ (w+1/3) 0 at frequencies ≫ fRD corresponding to modes re-entering horizon stiff-domination (SD), where frequency today scale SD-to-RD transition. We characterized in detail transfer function GW energy density...
Abstract We compute the detailed energy spectra of axions with two-photon coupling produced in stellar cores over a wide range masses. focus on main sequence stars and base our calculations interior profiles from MESA, for which we provide simple fits an appendix. The obtained axion spectra, combined recent models star formation history initial mass function, enable us to estimate properties diffuse background sourced by all universe. fluxes this its decay photons are subdominant but can...
The tentative identification of approximately ten relativistic anti-helium cosmic-ray events at AMS-02 would, if confirmed, challenge our understanding the astrophysical synthesis heavy anti-nuclei. We propose a novel scenario for enhanced production such anti-nuclei that is triggered by isolated, catastrophic injections large quantities energetic Standard Model (SM) anti-quarks in galaxy physics beyond (BSM). demonstrate SM anti-nucleosynthetic processes occur resulting rapidly expanding,...
The superradiant instability of black hole space-times has been used to place limits on ultra-light bosonic particles. We show that these are model dependent. While the initial growth mode is gravitational and thus independent, ability a limit new particles requires grow unhindered large number density. Non-linear interactions between particle other light degrees freedom mediated through higher dimension operators can damp this growth, eliminating limit. However, non-linearities may also...
Self-interactions within the dark sector could clump matter into heavy composite states with low number density, leading to a highly suppressed event rate in existing direct detection experiments. However, large interaction cross section between such ultraheavy (UHDM) and standard model results distinctive compelling signature; long, straight damage tracks as they pass through scatter matter. In this work, we propose using geologically old quartz samples large-exposure detectors for UHDM. We...
Gravitational waves (GW) produced in the early Universe contribute to number of relativistic degrees freedom, Neff, during Big Bang Nucleosynthesis (BBN) . By using constraints on we present a new bound how much could have expanded between horizon exit largest observable scales today and end inflation. We discuss implications inflationary models show affect model selection. also sensitivities current planned GW observatories such as LIGO LISA, that they impose are always less stringent than...
Recent studies reveal that more than a dozen of white dwarfs displaying near-perfect blackbody spectra in the optical range have been lurking Sloan Digital Sky Survey catalog. We point out that, way analogous to cosmic microwave background, these stars serve as excellent test beds for new physics. Specifically, we show how their observed lack spectral distortions translates into limits on parameter space axions with electromagnetic coupling. The prospects future improvements are also discussed.
We probe the cosmological consequences of a recently proposed class solutions to constant problem. In these models, universe undergoes long period inflation followed by contraction and bounce that sets stage for hot big bang era. A requirement any successful early model is it must reproduce observed scale-invariant density perturbations at cosmic microwave background (CMB) scales. While models involve inflation, inflationary Hubble scale during their observationally relevant stages or below...
Finite temperature effects in the Standard Model tend to restore electroweak symmetry early universe, but new fields coupled higgs field may as well reverse this tendency, leading so-called non-restoration (EW SNR) scenario. Previous works on EW SNR often assume that reversal is due thermal fluctuations of with negative quartic couplings higgs, and they find a large number are required. We observe can be minimally realized if field(s) develop(s) stable condensate. show one complex scalar...
We study the solar emission of light dark sector particles that self-interact strongly enough to self-thermalize. The resulting outflow behaves like a fluid which accelerates under its own thermal pressure highly relativistic bulk velocities in system. Compared ordinary noninteracting scenario, local has at least ∼10^{3} higher number density and correspondingly lower average energy per particle. show how this generic phenomenon arises composed millicharged self-interacting via photon....
The damping process of a homogeneous oscillating scalar field that indirectly interacts with thermal bath through mediator is investigated over wide range model parameters. We consider two types fields, those can decay to the and are individually stable but pair annihilate. former case has been extensively studied in literature by treating as local effect after integrating out assumed close-to-equilibrium field. same approach does not apply if freezes equilibrium. To account for latter case,...
Galactic double white dwarf (DWD) binaries are among the guaranteed sources for Laser Interferometer Space Antenna (LISA), an upcoming space-based gravitational wave (GW) detector. Most DWDs in LISA band far from merging and emit quasimonochromatic GWs. As these distributed throughout Milky Way, they experience different accelerations potential, therefore each DWD exhibits apparent GW frequency chirp due to differential acceleration between source LISA. We examine how influences parameter...
The tentative identification of approximately ten relativistic antihelium (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mover accent="true"><a:mi>He</a:mi><a:mo stretchy="true">¯</a:mo></a:mover></a:math>) cosmic-ray events at AMS-02 would, if confirmed, challenge our understanding the astrophysical synthesis heavy antinuclei. We propose a novel scenario for enhanced production such antinuclei that is triggered by isolated, catastrophic injections large quantities...
Dark matter may exist today in the form of ultraheavy composite bound states. Collisions between such dark states can release intense bursts radiation that includes gamma-rays among final products. Thus, indirect-detection signals include unconventional gamma-ray bursts. Such have been missed not necessarily because their low arriving fluxes, but rather briefness and rareness. We point out whose non-detection thus far are due to latter be detected near future with existing planned...
Minerals are solid state nuclear track detectors - recoils in a mineral leave latent damage to the crystal structure. Depending on and its temperature, features retained material from minutes (in low-melting point materials such as salts at few hundred degrees C) timescales much larger than 4.5 Gyr-age of Solar System refractory room temperature). The $O(50)$ MeV fission fragments left by spontaneous $^{238}$U other heavy unstable isotopes have long been used for dating geological samples....
Recent studies reveal that more than a dozen of white dwarfs displaying near-perfect blackbody spectra in the optical range have been lurking Sloan Digital Sky Survey catalog. We point out that, way analogous to Cosmic Microwave Background, these stars serve as excellent testbeds for new physics. Specifically, we show how their observed lack spectral distortions translates into limits on parameter space axions with electromagnetic coupling. The prospects future improvements are also discussed.
We compute the detailed energy spectra of axions with two-photon coupling produced in stellar cores over a wide range masses. focus on main sequence stars and base our calculations interior profiles from MESA, for which we provide simple fits an appendix. The obtained axion spectra, combined recent models star formation history initial mass function, enable us to estimate properties diffuse background sourced by all universe. fluxes this its decay photons are subdominant but can principle be...
We study the solar emission of light dark sector particles that self-interact strongly enough to self-thermalize. The resulting outflow behaves like a fluid which accelerates under its own thermal pressure highly relativistic bulk velocities in system. Compared ordinary non-interacting scenario, local has at least $\sim 10^3$ higher number density and correspondingly lower average energy per particle. show how this generic phenomenon arises comprised millicharged self-interacting via photon....