arXiv subjects

Bilguun Bayarsaikhan

Publications and source records attributed to Bilguun Bayarsaikhan.

5 recordsLinked to original sources

arXiv2026

Oscillon Floquet Modes and the Operators that Excite Them

We present the scattering modes of the oscillon, to the first three orders in the Fodor expansion, in terms of elementary functions. In the case of relativistic modes, these results are new. We use them to fully decompose the field and also to analytically invert the decomposition. In quantum field theory, this allows us to show that the corresponding creation and annihilation operators satisfy the usual oscillator algebra, extending to relativistic modes the demonstration that, at a fixed order in the Fodor expansion, a periodic oscillon state exists.

hep-th↗

arXiv2026

A Resonance in Elastic Kink-Meson Scattering

We analytically sum the leading bubble diagrams that contribute to the elastic scattering amplitude of a kink and a meson in the $ϕ^4$ double-well model. We find a single peak, corresponding to the unstable kink state in which the shape mode is excited twice. The peak has the usual Breit-Wigner form, and its imaginary part agrees with the shape mode decay rate found by Manton and Merabet.

hep-th↗

arXiv2026

Elastic Kink-Meson Scattering in the $Φ^4$ Double-Well Model

We calculate the leading order amplitude and probability for the elastic scattering of an elementary meson and a kink in the $ϕ^4$ double-well model. Classically, the kink is reflectionless, and so the leading contribution arises at one loop. At this order, the scattering amplitude exhibits a pole when the incoming meson energy is twice the shape mode energy, corresponding to the excitation of an unstable resonance with the twice excited shape mode. We expect that higher order corrections will give this resonance a width equal to the inverse of the known lifetime of this unstable excitation.

hep-th↗

arXiv2022

Dynamical analysis in regularized $4D$ Einstein-Gauss-Bonnet gravity with non-minimal coupling

We investigate the regularized four-dimensional Einstein-Gauss-Bonnet ($4D$ EGB) gravity with a non-minimal scalar coupling function, which is an extension of the regularized $4D$ EGB theory. By introducing non-minimal coupling to the Gauss-Bonnet term, we demonstrate the additional contribution to the dynamical equations which is otherwise absent in the dimensionally-regularized theory. Furthermore, we analyze the stability of the system by using the dynamical system approach based on fixed points. Then, we consider the time evolution to investigate the history of the universe and constraint with observational data to obtain the cosmological parameters of the model.

gr-qc↗

arXiv2020

Constraints on dark energy models from the Horndeski theory

In light of the cosmological observations, we investigate dark energy models from the Horndeski theory of gravity. In particular, we consider cosmological models with the derivative self-interaction of the scalar field and the derivative coupling between the scalar field and gravity. We choose the self-interaction term to have an exponential function of the scalar field with both positive and negative exponents. For the function that has a positive exponent, our result shows that the derivative self-interaction term plays an important role in the late-time universe. On the other hand, to reproduce the right cosmic history, the derivative coupling between the scalar field and gravity must dominate during the radiation-dominated phase. However, the importance of such a coupling in the present universe found to be negligible due to its drastic decrease over time. Moreover, the propagation speed of gravitational waves estimated for our model is within the observational bounds, and our model satisfies the observational constraints on the dark energy equation of state.

gr-qc↗