arXiv subjects

M. M. Chaichian

Publications and source records attributed to M. M. Chaichian.

4 recordsLinked to original sources

arXiv2026

Photon Propagation through Axion Clouds around Magnetized Compact Objects: Time Delays and Polarimetric Signatures

Temporal offsets between Gamma-Ray Bursts (GRBs) and high-energy neutrinos probe propagation effects in extreme astrophysical environments. We investigate whether such offsets can be generated by photon propagation through dense axion clouds gravitationally bound to strongly magnetized compact objects, such as canonical pulsars. Working within the Euler--Heisenberg effective theory extended by the axion sector, we derive the photon dispersion relations in a strong magnetic background permeated by an oscillating axion field. The magnetized vacuum is birefringent already at the Euler--Heisenberg level and the axion cloud superimposes density-dependent, time-dependent, and parity-odd structure on this baseline. The resulting geometry-dependent deviations from luminal propagation yield kinematic time delays reaching $Δt_{\perp} \simeq 9.3 \times 10^{-12}$ s for $\mathbf{k} \perp \mathbf{B}$, far too small to account for macroscopic multimessenger offsets, so that propagation through such environments cannot, by itself, rule out Lorentz-invariance violation as an explanation for GRB offsets. In the polarization sector, we show that the axion-induced circular birefringence is an endpoint effect and therefore does not produce a leading net rotation for a complete vacuum-to-vacuum transit through a localized cloud. For configurations with a nonzero axion-field endpoint contrast, the same parity-odd phase defines a conditional environmental sensitivity benchmark. We find that this mechanism is optimally sensitive in the ultralight regime, yielding a benchmark reach of $g_{aγγ} \lesssim 2.5 \times 10^{-10}\,\mathrm{GeV}^{-1}$ for canonical pulsar fields and axion masses near $m_a \sim 10^{-9}$ eV, and we identify the parity-odd (chiral) birefringence induced by the oscillating cloud as the signature that distinguishes the axion contribution from the calculable QED baseline.

hep-ph↗

arXiv2026

CPT Violation, Mirror World and Implications for Baryon Asymmetry

We propose a novel model in which the Universe is created as a pair of coordinate-reversed counterparts, forming a globally CPT-symmetric system that permits local CPT violations within each sector. This framework naturally introduces a mirror universe with opposite chiralities and reversed microscopic time coordinates, providing a geometric interpretation of time reversal without relying on initial-final state interchange. We investigate the consequences of local CPT violation in each universe, which induces a mass difference between the real inflaton and anti-inflaton fields. Such an asymmetry can modify reheating temperatures and naturally generate the observed matter-antimatter asymmetry in both universes.

hep-ph↗

arXiv2025

Very Special Relativity: Cherenkov Effect and an Analogy with Minkowski's Electrodynamics of Continuous Media

In this work, we explore the implications of the Cohen and Glashow Very Special Relativity (VSR) theory, a framework that introduces Lorentz invariance violation through the presence of a preferred direction. Our analysis focuses on the impact of VSR on the Cherenkov angle, revealing modifications to the dispersion relation of particles, particularly the photon and the electron, which acquire an effective inertial mass. This modification also implies a deviation in the speed of light, which can be constrained through precise experimental measurements. Using data from the RICH system of the LHCb experiment, we take advantage of its capability to reconstruct Cherenkov angles within the momentum range of the particles of 2.6-100 GeV/c. These measurements, combined with the most stringent laboratory tests of the isotropy of the speed of light ($Δc / c \sim 10^{-17}$), allow us to impose new upper bounds on the parameter $Ω$, which quantifies a deviation from the standard Special Relativity. Furthermore, we establish an analogy between VSR and Minkowski's electrodynamics in a dielectric medium for particles with very high velocity, offering a physically intuitive interpretation of the parameter $Ω$.

hep-ph↗

arXiv2022

Spin-1/2 "bosons'' with mass dimension 3/2 and fermions with mass dimension 1 cannot represent physical particle states

We delve into the first principles of quantum field theory to prove that the so-called spin-1/2 ''bosons'' and the fermions with mass dimension 1, including ELKO, cannot represent physical particle states with spin $1/2$. Specifically, we first demonstrate that both aforementioned fields are not invariant under rotational symmetry, which implies that the particles created for these fields are not eigenstates of the spin operator in the $(\frac{1}{2},0)\oplus(0,\frac{1}{2})$ representation of the Lorentz group, nor is it possible to construct a Hamiltonian density scalar under the rotational group from them. Furthermore, following Weinberg's approach to local causal fields, we prove that regardless of any discrete symmetry or adjoint structure, the relativistic fields in the $(\frac{1}{2}, 0) \oplus (0,\frac{1}{2})$ representation satisfy the Fermi-Dirac statistics in complete agreement with the well-established spin-statistics theorem and experimental results.

hep-th↗