arXiv subjects

Michael Sekatchev

Publications and source records attributed to Michael Sekatchev.

6 recordsLinked to original sources

arXiv2026

Design of ALPHA Phase I: A Plasma Haloscope for 10--20 GHz Post-Inflation Axions

The axion is a well-motivated hypothetical particle capable of resolving both the strong CP problem and the dark matter mystery, with recent post-inflationary cosmological simulations favoring masses above 40 {\mu}eV. Plasma haloscopes serve as a promising experimental approach to reach theoretically preferred sensitivities in this mass range. ALPHA, hosted at Yale Wright Laboratory, is an international collaboration developing plasma haloscopes to search for QCD dark matter axions. In this letter we present the detailed design and sensitivity projection for the first phase of the ALPHA experiment, which will search the mass range from 10 GHz to 20 GHz (~40 {\mu}eV to 80 {\mu}eV). This search will make use of wire-array plasma resonators to decouple the physical size from the resonant frequency, a limitation typically faced by traditional microwave cavities, allowing broadband sensitivity approaching KSVZ coupling strengths.

hep-ex↗

arXiv2025

The Glow of Axion Quark Nugget Dark Matter: (IV) CMB Spectral and Anisotropy Signatures

Axion quark nuggets (AQNs) are macroscopic dark-matter candidates, with masses of the order of a few grams to a kilogram and sub-micron radius, thought to form at the Quantum Chromo Dynamic era through axion-induced charge separation. This framework naturally links the dark and visible matter abundances ($\Omega_{\rm DM} \sim \Omega_{\rm visible}$) and provides a mechanism for generating the baryon-antibaryon asymmetry where dark matter is composed of matter AQNs and antimatter AQNs. Although behaving as cold dark matter on cosmological scales, baryons annihilate with antimatter AQNs, producing ionizing high-energy photons. The resulting energy injection may imprint spectral distortions on the cosmic microwave background (CMB) and modify the reionization history. Using a modified version of the \texttt{CLASS} Boltzmann code we compute the impact of this energy injection on the $\mu$ and $y$ spectral distortion parameters as well as on the optical depth. We find that (1) the CMB anisotropies remain essentially unaffected by baryon annihilation, and (2) the associated spectral distortion signatures lie within the sensitivity reach of proposed CMB spectral distortion missions. Finally, we discuss the similarities and differences between the AQN scenario and annihilating or decaying dark matter models.

astro-ph.CO↗

arXiv2025

The Glow of Axion Quark Nugget Dark Matter: (III) The Mysteries of the Milky Way UV Background

Axion quark nuggets (AQNs) are hypothetical objects with nuclear density that would have formed during the quark-hadron transition and could make up most of the dark matter today. These objects have a mass greater than a few grams and are sub-micrometer in size. They would also help explain the matter-antimatter asymmetry and the similarity between visible and dark components of the universe, i.e. $\Omega_{\text{DM}} \sim \Omega_{\text{visible}}$. These composite objects behave as cold dark matter, interacting with ordinary matter and producing pervasive electromagnetic radiation. This work aims to calculate the FUV electromagnetic signature in a 1 kpc region surrounding the solar system, resulting from the interaction between antimatter AQNs and baryons. To this end, we use the high-resolution hydrodynamic simulation of the Milky Way, FIRE-2 Latter suite, to select solar system-like regions. From the simulated gas and dark matter distributions in these regions, we calculate the FUV background radiation generated by the AQN model. We find that the results are consistent with the FUV excess recently confirmed by the Alice spectrograph aboard New Horizons, which corroborated the FUV excess initially discovered by GALEX a decade ago. We also discuss the potential cosmological implications of our work, which suggest the existence of a new source of FUV radiation in galaxies, linked to the interaction between dark matter and baryons.

astro-ph.CO↗

arXiv2024

Stochastic Approaches to Asset Price Analysis

In this project, we propose to explore the Kalman filter's performance for estimating asset prices. We begin by introducing a stochastic mean-reverting processes, the Ornstein-Uhlenbeck (OU) model. After this we discuss the Kalman filter in detail, and its application with this model. After a demonstration of the Kalman filter on a simulated OU process and a discussion of maximum likelihood estimation (MLE) for estimating model parameters, we apply the Kalman filter with the OU process and trailing parameter estimation to real stock market data. We finish by proposing a simple day-trading algorithm using the Kalman filter with the OU process and backtest its performance using Apple's stock price. We then move to the Heston model, a combination of Geometric Brownian Motion and the OU process. Maximum likelihood estimation is commonly used for Heston model parameter estimation, which results in very complex forms. Here we propose an alternative but easier way of parameter estimation, called the method of moments (MOM). After the derivation of these estimators, we again apply this method to real stock data to assess its performance.

q-fin.ST↗

arXiv2024

The Glow of Axion Quark Nugget Dark Matter: (I) Large Scale Structures

Axion quark nuggets (AQNs) are hypothetical objects with a mass greater than a few grams and sub-micrometer size, formed during the quark-hadron transition. Originating from the axion field, they offer a possible resolution of the similarity between visible and dark components of the Universe. These composite objects behave as cold dark matter, interacting with ordinary matter and resulting in pervasive electromagnetic radiation throughout the Universe. This work aims to predict the electromagnetic signature in large-scale structures from the AQN-baryon interaction, accounting for thermal and non-thermal radiations. We use Magneticum hydrodynamical simulations to describe the distribution and dynamics of gas and dark matter at cosmological scales. We calculate the electromagnetic signature from radio, starting at $\nu \sim$ 1 GHz, up to a few keV X-ray energies. We find that the AQNs signature is characterized by monopole and fluctuation signals. The amplitude of both signals strongly depends on the average AQN mass and the ionization level of the baryonic environment. We identify a most optimistic scenario with a signal often near the sensitivity limit of existing instruments, such as FIRAS and the South Pole Telescope for high-resolution. Fluctuations in the Extra-galactic Background Light caused by the AQN can be tested with space-based imagers Euclid and James Webb Space Telescope. We also identify a minimal configuration, still out of reach of existing instruments, but future experiments might be able to pose constraints on the AQN model. We conclude that this is a viable dark matter model, which does not violate the canons of cosmology, nor existing observations. The best chances for testing this model reside in 1) ultra-deep IR and optical surveys, 2) spectral distorsions of the CMB and 3) low-frequency (1 GHz < $\nu $ < 100 GHz) and high-resolution ($\ell > 10^4$) observations.

astro-ph.CO↗

arXiv2023

Chaotic Dynamics of a Dripping Water Faucet

An experimental approach is taken to study the dynamics of the dripping water faucet, a simple deterministic system. The time interval between successive drops may be affected by the many drops preceding it. The time interval is predicted by numerical simulations to exhibit increasingly chaotic behavior with increasing flow rate, showing transitions from single period to period-m ($m=2,4,8,16,...$) dripping, followed by a purely chaotic regime. Deterministic regimes are identified through plots of the time interval against drop number and against successive time interval, and through a bifurcation diagram, but the dripping faucet does not traverse them sequentially as anticipated numerically. Understanding the chaotic dynamics of the dripping faucet will aid in the study of more complex chaotic systems, of which there are a plethora across many disciplines.

physics.flu-dyn↗