arXiv subjects

Dominik Szczęśniak

Publications and source records attributed to Dominik Szczęśniak.

8 recordsLinked to original sources

arXiv2024

Thermodynamics of the Van der Waals black hole within nonextensive Kaniadiakis entropy

In this work, we have studied the thermodynamic properties of the Van der Waals black hole in the framework of the nonextensive Kaniadakis entropy. We have shown that the black hole properties, such as the mass and temperature, differ from those obtained by using the the Boltzmann-Gibbs approach. Moreover, the nonextensivity \k{appa}-parameter changes behavior of the Gibbs free energy via introduced thermodynamic instabilities, whereas the emission rate is influenced by \k{appa} only at low frequencies. Nonetheless, the pressure-volume (P(V)) characteristics are found independent of \k{appa} and the entropy form, unlike in other anti-de Sitter (AdS) black hole models. In summary, presented findings partially support previous arguments of Gohar and Salzano that under certain circumstances all entropic models are equivalent and indistinguishable [1].

gr-qc↗

arXiv2024

Novel properties of two-dimensional Janus transition metal hydrosulfides: electride states, charge density waves and superconductivity

Inspired by recent experimental synthesis of the two-dimensional Janus material MoSH, we have performed extensive first-principles calculations to investigate the characteristics of all possible Janus two-dimensional transition metal hydrosulfides (JTMSHs), in both the 2H and 1T phases. Our investigations revealed that the JTMSHs can form a unique family of two-dimensional materials with intriguing physical and chemical properties. In details, we have found that JTMSHs can exist in various states, exhibiting metallic, semiconducting, and magnetic character. One particularly intriguing finding considered identification of electride states with distinct bonding characteristics in the 2H-JTMSHs for TM=V, Nb, Ta, Mo, W and Tc. Additionally, we have observed evidence of charge density wave scenario in 1T-JTMSH with TM=Tc, Re, and W and 2H-JTMSH with TM = Tc. Importantly, by applying compressive strain to these materials, the charge density wave can be completely suppressed, eventually leading to the superconducting phase. In particular, we have shown that when subjected to a compressive strain within 10%, the superconducting transition temperature (TC) of 1T-WSH, 1T-TcSH and 2H-TcSH can reach values of 13.8, 16.2 and 24.2 K respectively. Moreover, our investigation also unveiled two intrinsic phonon-mediated superconductors, namely 2H-WSH and 1T-RuSH with TC of 17.0 and 8 K, respectively.

cond-mat.mtrl-sci↗

arXiv2024

Coherence of multipartite quantum states in the black hole quantum atmosphere

According to the recently introduced concept of quantum atmosphere, the black hole radiation is suggested to originate from the quantum excitations at the effective distance ($r$) near the event horizon ($r_H$). Here, this concept is explored from the quantum resource perspective by analysing the coherence of multipartite quantum systems located near a black hole. For the Greenberger-Horne-Zeilinger state, it is found that signatures of the atmosphere are apparent. This is to say, the coherence exhibits peak close to the event horizon and next decreases, recovering conventional behavior at $r/r_H \rightarrow\infty$. Interestingly, it is shown that as the quantum state gets more complex and the number of parties increases, the role of quantum atmosphere diminishes and the standard behaviour expected for the $N$-partite coherence quantifiers can be observed. That means, in case of complex setups the quantum atmosphere signatures may not be detectable. Hence, our findings show that care should be taken, regarding size of a system, when quantum atmosphere argument is considered.

gr-qc↗

arXiv2023

The hybrid cosmology in the scalar-tensor representation of $f(\mathcal{G},T)$ gravity

In this work, the $f(\mathcal{G},T)$ theory of gravity is recast in terms of the $ϕ$ and $ψ$ fields within the scalar-tensor formulation, where $\mathcal{G}$ is the Gauss-Bonnet term and $T$ denotes the trace of the energy-momentum tensor. The general aspects of the introduced reformulation are discussed and the reconstruction of the cosmological scenarios is presented, focusing on the so-called hybrid evolution. As a result, the scalar-tensor $f(\mathcal{G},T)$ theory is successfully reconstructed for the early and late time approximations with the corresponding potentials. The procedure of recovering the $f(\mathcal{G},T)$ theory in the original formulation is performed for the late time evolution and a specific quadratic potential. The scalar-tensor formulation introduced herein not only facilitates the description of various cosmic phases but also serves as a viable alternative portrayal of the $f(\mathcal{G},T)$ gravity which can be viewed as an extension of the well-established scalar Einstein-Gauss-Bonnet gravity.

gr-qc↗

arXiv2023

Cosmological aspects of the unimodular-mimetic $f(\mathcal{G})$ gravity

In this work we introduce and study the unimodular-mimetic $f(\mathcal{G})$ gravity, where unimodular and mimetic constraints are incorporated through corresponding Lagrange multipliers. We present field equations governing this theory and discuss their main properties. By using the reconstruction scheme, we obtain quadratic unimodular-mimetic $f(\mathcal{G})=A\mathcal{G}^2$ gravity capable of describing hybrid expansion law and the power law evolution. Furthermore, we employ an inverted reconstruction technique in order to derive specific $f(\mathcal{G})$ function that reproduces the Hubble rate of symmetric bounce. The unimodular-mimetic $f(\mathcal{G})=A\mathcal{G}^2$ is also shown to be compatible with the BICEP2/Keck and Planck data. To this end, we incorporate updated constraints on the scalar-to-tensor ratio and spectral index, utilizing a perfect fluid approach to the slow-roll parameters. Through an analysis of that kind, we demonstrate that the theoretical framework presented here can indeed characterize inflation that agrees with the observational findings. Consequently, the introduced extension appears to have potential to describe and encompass a wide spectrum of cosmological models.

gr-qc↗

arXiv2023

Signatures of the black hole quantum atmosphere in nonlocal correlations

Recently, it was suggested that the Hawking radiation may originate not at the event horizon but in the quantum region outside of it, known as the quantum atmosphere. The present study attempts to explore this argument further by assessing its role in shaping quantum correlations near a black hole. Herein, these are conveniently captured within the geometric measure of nonlocality, termed as the measurement-induced nonlocality, and found to exhibit signatures of the atmosphere. In particular, a notable loss of correlations is observed well outside the event horizon, coinciding with the peak of particles radiation in the atmosphere region. Still, the correlations are shown to be always finite therein and to continuously scale with not only the radiation temperature but also with the horizon size. Hence, some characteristics of the atmosphere appears to be detectable at the quantum correlations level, providing novel insight and means to help verify the concept of interest.

gr-qc↗

arXiv2021

Cosmology in the mimetic higher-curvature $f(R, R_{μν}R^{μν})$ gravity

In the framework of the mimetic approach, we study the $f(R,R_{μν}R^{μν})$ gravity with the Lagrange multiplier constraint and the scalar potential. We introduce field equations for the discussed theory and overview their properties. By using the general reconstruction scheme we obtain the power law cosmology model for the $f(R,R_{μν}R^{μν})=R+d(R_{μν}R^{μν})^p$ case as well as the model that describes symmetric bounce. Moreover, we reconstruct model, unifying both matter dominated and accelerated phases, where ordinary matter is neglected. Using inverted reconstruction scheme we recover specific $f(R,R_{μν}R^{μν})$ function which give rise to the de-Sitter evolution. Finally, by employing the perfect fluid approach, we demonstrate that this model can realize inflation consistent with the bounds coming from the BICEP2/Keck array and the Planck data. Thus, it is suggested that the introduced extension of the mimetic regime may describe any given cosmological model.

gr-qc↗

arXiv2018

Unexpected Xe cations and superconductivity in Y-Xe compounds under pressure

The metal-based noble gas compounds exhibit interesting behavior of electronic valence states under pressure. For example, Xe upon compression can gain electrons from the alkali metal, or lose electrons unexpectedly to Fe and Ni, toward formation of stable metal compounds. In addition, the Na2He is not even stabilized by the local chemical bonds but via the long-range Coulomb interactions. Herein, by using the first-principles calculations and the unbiased structure searching techniques, we uncover that the transition metal Y is able to react with Xe above 60 GPa within various Y-Xe stochiometries, namely the YXe, YXe2, YXe3 and Y3Xe structures. Surprisingly, it is found that all the resulting compounds are intermetallic and Xe atoms are positively charged. We also argue that the pressure-induced changes of the energy orbital filling are responsible for the electron transfer from Xe to Y. Meanwhile, the Peierls-like mechanism is found to stabilize the energetically most favorable YXe-Pbam phase. Furthermore, the predicted YXe-Pbam, YXe-Pnnm, and YXe3-I4/mcm phases are discovered to be phonon-mediated superconductors under pressure, with the critical superconducting temperatures in the range of approximately 3-4K, 7-10K, and 5-6K, respectively. In summary, our work promotes further understanding of the crystal structures and electronic properties of the metal-based noble gas compounds.

cond-mat.mtrl-sci↗