arXiv subjects

Zurab Kepuladze

Publications and source records attributed to Zurab Kepuladze.

8 recordsLinked to original sources

arXiv2026

Overlapping resonance branches of a gauge-invariant Lorentz-violating massive vector

We investigate the propagation and resonance behavior of an Abelian massive vector field in the presence of a gauge-invariant, CPT-even, dimension-four Lorentz-violating kinetic operator constructed from a single preferred four-vector. In the massless theory, the propagator contains an additional algebraic pole that decouples from conserved currents, leaving two physical degrees of freedom. After spontaneous breaking of the internal U(1) symmetry, all three vector polarizations become physical but separate into two orthogonal dispersion branches carrying two and one physical polarization states, respectively. We show that this decomposition is preserved under Dyson resummation for a transverse matter vacuum polarization and calculate the corresponding decay rates and fermion-annihilation amplitude. The split-pole structure and associated double resonance behavior cannot be understood through a finite number of perturbative Lorentz-violating insertions. The contribution of the second branch in physical processes is strongly dependent on the initial momentum geometry: it vanishes for massless head-on fermions in a timelike background, whereas boosted nearly parallel configurations can generate an energy-enhanced correction. Spacelike and lightlike backgrounds additionally lead to directional and potentially sidereal variations of the resonance signal.

hep-ph↗

arXiv2026

Lorentz-Violating Photon Decay into Neutrinos and Constraints from PeV Photon Stability

We study the vacuum decay of a Lorentz-violating photon into a neutrino-antineutrino pair. Lorentz-violating corrections to the photon dispersion relation are parametrized through an effective invariant mass $m_{\mathrm{eff}}^{2}=k_αk^α$. This makes the otherwise forbidden decay $γ\toν\barν$ kinematically allowed. The process proceeds through the Standard Model one-loop neutrino electromagnetic vertex and is therefore strongly suppressed. Using the low-$q^{2}$ anapole form factor, we derive the decay rate and apply it to TeV and PeV photons. We find that below the electron-positron threshold the neutrino channel is open but generally too slow to provide stronger constraints than existing bounds. Above the threshold, $γ\to e^{+}e^{-}$ dominates unless the relative photon-electron LIV parameter closes this channel. In that case, the neutrino decay gives an independent constraint on photon-neutrino relative LIV parameters.

hep-ph↗

arXiv2026

Unavoidable Loop-Induced Quintessence -- Higgs Mixing and Its Phenomenological Consequences

We investigate a class of quintessence models in which the dark-energy scalar field interacts with sterile neutrinos responsible for neutrino mass generation through the seesaw mechanism. Radiative corrections involving sterile neutrinos induce Higgs-quintessence mixing and provide an effective portal between quintessence and Standard Model particles. We calculate the corresponding one-loop mixing amplitude and show that its structure depends on the relation between the characteristic momentum transfer and the sterile-neutrino mass. In the low-momentum regime the mixing is effectively kinetic, while at high energies it acquires a mass-mixing form. A notable result is that the overall suppression of the induced mixing is governed by the physical neutrino mass scale, leading to a predictive relation between neutrino properties and Higgs-quintessence interactions. The resulting loop-induced effects are found to be suppressed by factors comparable to those controlling the tree-level quintessence-neutrino interaction. The induced mixing generates effective couplings of quintessence to Standard Model fermions and gauge bosons, leading to modified Higgs, W and Z boson processes and opening decay channels for the quintessence field, which may prove to be cosmologically important. While the corresponding effects remain well below current experimental sensitivities in the minimal heavy-seesaw scenario, the framework establishes a direct connection between dark-energy dynamics, neutrino mass generation and Higgs-sector phenomenology and provides a basis for studying scenarios with lighter sterile neutrino states where observable effects may be enhanced.

hep-ph↗

arXiv2026

Lorentz Violation: Loop-Induced Effects in QED and Observational Constraints

Lorentz invariance is a cornerstone of modern physics, yet its possible violation remains both theoretically intriguing and experimentally significant. In this work, using quantum electrodynamics as an example, we explore how Lorentz invariance violation, introduced into a specific sector of the theory, spreads through loop corrections, modifying the propagation and dispersion relations of other particles. Self-energy and vacuum polarization graphs reveal how LIV effects transfer across sectors, influencing particle kinematics. Due to these loop effects, constraints from cosmic-ray observations and other Earth-based experiments impose limits on induced LIV parameters that would otherwise be less constrained. We show that while interaction-based LIV effects require unrealistically large parameters for detection, modifications to dispersion relations can be probed down to $δ\sim 10^{-8} \text{ to } 10^{-9}$ at the LHC. This suggests that accelerator-based resonance studies provide a promising avenue for stringent LIV constraints, potentially rivaling astrophysical observations.

hep-ph↗

arXiv2025

Probing Lorentz Invariance Violation in Z Boson Mass Measurements at High-Energy Colliders

We propose a minimal extension to the Standard Model by introducing a Lorentz Invariance Violation (LIV) term into the Z boson's dispersion relation, expressed as $p_μp^μ= M_Z^2 + δ_{LIV} (p_μn^μ)^2$, where $δ_{LIV}$ defines the violation scale and $n^μ$ is a unit Lorentz vector specifying the direction. This modification alters the Z boson propagator and decay rate, impacting the Drell-Yan process cross-section at high-energy colliders. Observable effects are most pronounced near the resonance region at high rapidities ($|Y| > 4$), potentially shifting the perceived Z boson mass and inducing sidereal-time modulations for spacelike and lightlike LIV due to Earth's rotation. We outline a targeted search strategy for ATLAS and CMS, achieving sensitivity to LIV signatures down to $|δ_{LIV}| \approx 10^{-8}$ (or $10^{-9}$ optimistically), offering new insights into historical and future collider data. Our model predicts systematic shifts in weak boson masses at higher collision energies, relevant to past Tevatron and LHC discrepancies, though current data are now consistent.

hep-ph↗

arXiv2021

A new take on the inflationary quintessence

The quintessence field coupled to the cosmic neutrino background (CNB) has been widely discussed as an alternative mechanism to address the coincidence problem. As it is well known, it is possible to extend such models to obtain quintessential inflation, that is, to incorporate inflationary stage as well. Taking an alternative route, one can start from the well established inflationary models and obtain successful quintessence models at the expense of coupling with the CNB. To Follow this route, we use a slightly reformulated model addressed in PRD95, 123521 (2017). This particular model assumes $\mathcal{Z}_2$ symmetry for both scalar field potential and coupling term, which then breaks down in course of the cosmological evolution. For our discussion, however, the $\mathcal{Z}_2$ symmetry of the potential is not mandatory the model to work. The conventional mechanism of particle production by the oscillating inflaton field (and their subsequent thermalization) remains operative. It is plain to see that the proposed construction can be easily applied for many successful models of inflation to incorporate dark energy at the expense of coupling with the CNB. We address the issue of neutrino nuggets from the quantum field theory point of view. Namely, these nuggets are considered as bound states caused basically by the Yukawa force, which arises in the framework of linear perturbation theory due to exchange of virtual quanta of quintessence field between the neutrinos.

astro-ph.CO↗

arXiv2012

Quantization of AdS x S particle in static gauge

We quantize the particle dynamics in AdS_{N+1} x S^M spacetime in static gauge, which leads to the coordinate representation with wave functions depending only on spatial coordinates. The energy square operator is quadratic in canonical momenta and contains a scalar curvature term. We analyze the self-adjointness of this operator and calculate its spectrum. We then construct unitary representations of the isometry group SO(2,N) x SO(M+1) and calculate the quantum relation between the Casimir numbers.

hep-th↗

arXiv2012

On particle type string solutions in AdS_3 x S^3

The AdS_3 x S^3 string dynamics is described in a conformal gauge using the SL(2,R) and SU(2) group variables as the target space coordinates. A subclass of string surfaces with constant induced metric tensor on both AdS_3 and S^3 projections is considered. The general solution of string equations on this subclass is presented and the corresponding conserved charges related to the isometry transformations are calculated. The subclass of solutions is characterized by a finite number of parameters. The Poisson bracket structure on the space of parameters is calculated, its connection to the particle dynamics in SL(2,R) x SU(2) is analyzed and a possible way of quantization is discussed.

math-ph↗