arXiv subjects

Kirill Zatrimaylov

Publications and source records attributed to Kirill Zatrimaylov.

7 recordsLinked to original sources

arXiv2026

Yukawa modification of Traversable Wormholes supported by Holographic Dark Energy

Inspired by holographic dark energy models, we extend the analysis performed in Ref.\cite{RGPC} taking into account Yukawa deformations on the different energy density (HDE) profiles. The profiles we have explored are: the Bekenstein-Hawking HDE, the Moradpour energy density, the Standard Renyi HDE and the Mixed Energy Density. With the help of an inhomogeneous Equation of State of the form $p_{r}(r)=ω_{r}\left( r\right) ρ(r)$, we have considered Zero Tidal Forces. Differently from the original case, only a particular case of the family of the Bekenstein-Hawking HDE profiles distorted by the Yukawa term has developed a divergent $ω_{r}\left( r\right) $ for $r\rightarrow \infty $. To cure such a divergence we have introduced a modification at large distances in order to have a finite result. This means that the Zero Tidal Forces can be imposed in a very large but limited region of the spacetime. Such modification did not change the behavior of the Equation of State close to the throat. For every proposal we have computed the components of the Stress-Energy Tensor. What we have found is that the Yukawa-Bekenstein-Hawking HDE is the only positive profile, while the Yukawa-Moradpour and the Yukawa-Renyi have a limited region where the energy density is positive. The remaining Yukawa-Mixed Energy Density is always negative. This means that the Yukawa distortion introduces a kind of negative energy density.

gr-qc↗

arXiv2026

Traversable Wormholes induced by polytropic $n=1$ energy density

We investigate spherically symmetric and static traversable wormholes supported by exotic matter, focusing on solutions sourced by physically motivated dark matter energy density profiles. Considering the polytropic $n=1$ (Lane-Emden) distribution, we construct explicit forms of the shape function $b(r)$ and analyze the resulting radial and tangential pressures, carefully addressing the requirements of the flare-out condition at the throat and the absence of horizons. We explore zero-tidal-force configurations as well as inhomogeneous equations of state, demonstrating how appropriate choices of the radial pressure allow for finite and well-behaved redshift functions throughout the spacetime. Boundary conditions at a finite radius are implemented to ensure vanishing energy density and pressures, and asymptotic expansions are derived to characterize the behavior of the metric and matter content near the edge of the dark matter halo. Additionally, we reformulate the Einstein field equations entirely in terms of the energy density, radial and tangential pressures, and their derivatives, providing a framework to analyze the matter distribution independently of the explicit metric functions. Our results offer a systematic methodology to construct physically consistent wormhole geometries supported by realistic dark matter halos, highlighting the intricate interplay between matter profiles, equations of state, and geometric constraints.

gr-qc↗

arXiv2026

Warp Drive in a De Sitter Universe

Generalizing the result of H. Ellis who embedded a warp bubble in the background of a black hole, we introduce a warp bubble in a de Sitter universe. We show that under certain conditions (namely, that the bubble is moving in the radial direction at a velocity equal to the speed of the expansion of the universe), it is possible for the bubble to have strictly non--negative energy density, with the weak and null energy satisfied up to a total divergence term that averages to zero. We discuss the implications of this result and its possible applications to models of dark energy like "dark fluid" and quintessence, as well as to physical systems like Casimir cavities and analogue gravity setups.

gr-qc↗

arXiv2026

Macroscopic "Lola/Mola" Cat State

We present the first--ever example of a macroscopic system in a quantum superposition. The system in question is a Siamese cat known as Lola; however, on a time scale of about 12 hours it oscillates into a different state that we refer to as "Mola". In the "Lola" state, the system is sweet and friendly and allows to cuddle itself, but in the "Mola" state, it is malevolent and witchy. When the probability of the system being in the "Mola" state is high, decoherence is strongly discouraged!

physics.pop-ph↗

arXiv2024

Black Holes, Warp Drives, and Energy Conditions

Following the work of H. Ellis, we study warp drives in the gravitational field of a Schwarzschild black hole. We find that as long as the warp drive crosses the black hole horizon at a subluminal speed, the horizon would be effectively absent inside the warp bubble. Moreover, we discover that the black hole's gravitational field can alleviate the violations of the weak energy condition (WEC) and the null energy condition (NEC) and therefore decrease the amount of negative energy required to sustain a warp drive, which may be instrumental for creating microscopic warp drives in lab experiments. We also consider the thermodynamics of a warp bubble interacting with a black hole and point out some paradoxes that may indicate a gap in our understanding of them from the thermodynamic point of view.

gr-qc↗

arXiv2023

Black Holes and Warp Drive

We study the generalizations of the original Alcubierre warp drive metric to the case of curved spacetime background. We find that the presence of a horizon is essential when one moves from spherical coordinates to Cartesian coordinates in order to avoid additional singularities. For the specific case of Schwarzschild black hole, the horizon would be effectively absent for the observers inside the warp bubble, implying that warp drives may provide a safe route to cross horizons. Moreover, we discover that the black hole's gravitational field can decrease the amount of negative energy required to sustain a warp drive, which may be instrumental for creating microscopic warp drives in lab experiments. A BEC model is also introduced to propose possible test in the Analogue Gravity framework.

gr-qc↗

arXiv2021

Dark Matter, Rotation Curves, and the Morphology of Galaxies

In this thesis, we investigate some aspects of dark matter phenomenology and its predictive power in explaining the flattening of galaxy rotation curves at large distances. After outlining the Standard Model of particle physics, its symmetries and possible extensions in Chapter 2, we review key facts about dark matter and various types of dark matter models in Chapter 3. In Chapter 4 we discuss some alternatives to cold dark matter, which include modified Newtonian dynamics (MOND), superfluid dark matter and emergent gravity, and highlight the difficulties that are encountered in attempts to extend these frameworks to full-fledged relativistic settings. In Chapter 5 we turn to explore a completely different option, namely that flattened rotation curves reflect the presence of prolate dark-matter bulges or string-like objects around galaxies, without the need for any infrared modification of gravity. To test this model, we fit a number of galaxy rotation curves and find that the presence of a string-like filament yields improvement in fit quality of about 40-70 % in some cases, while the deformation of a dark halo yields only modest improvement by about 6-7 %. In Chapter 6 we collect some concluding remarks.

astro-ph.CO↗