In this paper, we investigate the thermodynamic properties of spherically symmetric, static black hole solutions within the framework of Conformal Killing Gravity (CKG). This is a modified theory of gravity that retains all solutions of General Relativity, while addressing some of its theoretical shortcomings and enriching gravitational phenomenology at large distances. We derive key thermodynamic quantities, including mass, temperature, heat capacity and Gibbs free energy, to examine the stability and phase structure of extended Schwarzschild–AdS and charged AdS black holes. Furthermore, employing the formalism of geometrothermodynamics, we analyze the behavior of the thermodynamic curvature scalar to identify critical points and characterize phase transitions. Our results demonstrate that the parameter $$ \lambda ,$$ which quantifies deviations from Einstein’s theory, plays a pivotal role in shaping the thermodynamic behavior, resulting in new stability conditions and distinct phase transition patterns compared to those predicted by standard General Relativity.

Iran

S. Ghaffari

Spain

G. Luciano

Black hole thermodynamics in Harada’s inspired theory of gravity: stability, phase structure and geometrothermodynamics

We demonstrate that the polaron theory from solid state physics can serve as an interesting analogue model for non-perturbative QCD, at least in the description of nucleons and related low-energy physics of strong interactions. By drawing explicit analogies between polaron physics, arising for an electron moving in an ionic crystal, and physics of pion-nucleon interactions, certain rules for the “polaron/QCD correspondence” are proposed. In polaron theory, the effective fermion mass as a function of the coupling constant is known both in the weak and strong coupling limits. The conjectured “polaron/QCD correspondence” translates these results into strong interactions. It is then shown how application of these rules leads to unexpectedly good quantitative predictions for the nucleon mass and pion-nucleon sigma term. The polaron approach also predicts that the quark degrees of freedom in the form of the constituent quark account for onethird of the nucleon mass, consistent with lattice predictions. We discuss possible physical reasons underlying the observed quantitative similarity between polaron physics and non-perturbative QCD.

Russia

S. Afonin

A. Tulub

Quark model of nucleon based on an analogy with polaron

We study the thermal behavior of quarkonia and fully-heavy tetraquark states associated to the charmonium, bottomonium and bottom-charmonium mass spectra. The starting point is the Schrödinger formalism with a vacuum Cornell-like potential. The spin-spin, spin-orbit and tensor contributions are also considered to describe the structure of the vacuum quarkonia $$Q\bar{Q}$$ spectra ($\textit{Q}$ denoting $\textit{c}$, $\textit{b}$ quarks). The parameters of the model are fixed using the experimental data of the $$Q\bar{Q}$$ states. After that, this formalism is extended to the fully-heavy tetraquark states within the $$1^3 S_1$$ axial diquark– $$1^3 S_1$$ axial antidiquark configuration $$[QQ] [\bar{Q} \bar{Q}]$$ , and their vacuum mass spectra are obtained and compared to the experimental data recently obtained. Our predictions support the interpretation of the $\textit{X}$(6600) (or $\textit{X}$(6552)), $\textit{X}$(6900) and $\textit{X}$(7200) states as the radially-excited $$T_{4c}(n^1S_0)$$ configurations with $$n=2,3,4$$ . In the sequence, we evaluate the mass spectra behavior in a thermal medium, by introducing a modified temperature-dependent Cornell potential. As a consequence, this formalism enables us to get some insight into the dissociation mechanism of $$[QQ] [\bar{Q} \bar{Q}]$$ states caused by a thermal medium, and into the temperature range at which the tetraquark states might be formed. We find that these structures cannot be formed in the thermal medium when the system has a temperature higher than about twice the critical temperature. These findings may be useful to better understand the features of the exotics in heavy-ion collisions.

Brazil

Vinícius Silva

Cássio Pigozzo

Luciano Abreu

Fully-heavy tetraquarks in the vacuum and in a hot environment

The late-time cosmological expansion within a flat Friedmann–Lemaître–Robertson–Walker (FLRW) spacetime is studied using a model characterized by bulk viscous dark matter (bulk viscosity $$\zeta = \zeta _0 \rho _m H^{-1}+\zeta _1 H $$ , $$\zeta _0$$ & $$\zeta _1$$ are constants, and $\textit{H}$, the Hubble parameter) interacting with a decaying vacuum density $$\rho _{\Lambda } = \mathcal {C}_0 + 3\nu H^2$$ , where $$\mathcal {C}_0$$ and $$\nu $$ are constants. The bulk viscous pressure is described by Eckart’s theory. The interaction term is defined as $$ Q=3H\alpha (\rho _m+\rho _\Lambda )$$ , where $$\alpha $$ , the interaction parameter. Analytical solutions for the Hubble parameter and the scale factor have been derived. The validity of the models is evaluated by constraining their free parameters using observational data from $\textit{Cosmic Chronometer}$, the $\textit{Pantheon}$, and a combination of both datasets. The goodness of fit is assessed by minimizing the $$\chi ^2$$ function utilizing the Markov Chain Monte Carlo (MCMC) method. Selection information criteria, namely AIC and BIC, have been obtained to analyze the models’ stability. Additionally, several essential cosmological parameters characterizing the evolution dynamics are estimated and discussed analytically, and compared with the $$\Lambda $$ CDM model. The proposed model suggests a transition from the deceleration to the acceleration phase, indicating thermodynamic equilibrium in the distant future, aligning with the $$\Lambda $$ CDM model. The model shows a slight deviation from $$\Lambda $$ CDM model and effectively reduces the $$H_0$$ tension between local measurements by $\textit{R}$21 and global measurements by Planck 2018. The model is consistent with thermodynamic laws and upholds the second law of thermodynamics. Finally, Phase-space analysis supports the same evolutionary transitional phases.

India

Tanmay Nandi

Amitava Choudhuri

Bulk viscous matter interacting with decaying vacuum energy density: a model for late-time evolution of the Universe

In this paper, we investigate the dynamics of a non-Hermitian Su-Schrieffer-Heeger model that arises out of the no-click limit of a monitored SSH model in the Krylov space. We find that the saturation timescale of the complexity associated with the spread of the state in the Krylov subspace increases with the measurement rate, and late time behaviour differs across the PT symmetry transition point. Furthermore, extending the notion of this complexity for subsystems in Krylov space, we find that the scaling of its late time value with subsystem size shows a discontinuous jump across the PT transition point, indicating that it can be used as a suitable order parameter for such transition but not for the measurement-induced transition. Finally, we show that a generalized measure in the Krylov subspace, which contains information about the correlation landscape, such as Quantum Fisher information, which also possesses some structural similarity with the complexity functional, can be a promising probe of the measurement-induced phase.

Nilachal Chakrabarti

Neha Nirbhan

Arpan Bhattacharyya

Dynamics of monitored SSH model in Krylov space: from complexity to quantum Fisher information

Scalar singlets under the Standard Model gauge group appear naturally in many well-motivated New Physics scenarios, such as the composite Higgs models. Unlike the Higgs boson in the Standard Model, they can induce large flavour-changing neutral currents (FCNCs) in the top sector. We investigate systematically the effects of a light scalar singlet $\textit{S}$ with top-quark FCNC couplings, by including the low-energy constraints from the $\textit{B}$ → $\textit{μ}$ decay, the muon anomalous magnetic moment ($\textit{g}$ − 2) and the neutron Electric Dipole Moment (EDM). We also perform a detailed Monte-Carlo simulation of the channel $\textit{pp}$ → $\textit{tS}$ + $\textit{j}$ with $\textit{S}$ → $\textit{μ}$ and $\textit{S}$ → $$ b\overline{b} $$ , and investigate the LHC sensitivity to the $\textit{tcS}$ couplings. It is found that the scalar singlet $\textit{S}$ can induce scalar-type contributions to the $\textit{B}$ $\textit{→ μ}$ decay, which do not suffer from the helicity suppression and contain a large CKM factor $$ {V}_{cs}^{\ast }{V}_{tb} $$ . As a result, constraints on the $\textit{tcS}$ couplings from the measured branching ratio $$ \mathcal{B} $$ ($\textit{B}$ → $\textit{μ}$ ) are quite stringent, being even stronger than the expected LHC sensitivity in some parameter spaces. Besides the CP-conserving $\textit{tcS}$ couplings, we have also considered the case of CP-violating $\textit{tcS}$ couplings, with $$ {y}_{R,L}^{ct}=\left|{y}_{R,L}^{ct}\right|{e}^{i{\theta}_{R,L}} $$ . It is found that the CP observables $$ {\mathcal{A}}_{\Delta {\varGamma}_s}^{\mu \mu} $$ and $$ {\mathcal{S}}_{\mu \mu} $$ of the $\textit{B}$ $\textit{→ μ}$ decay are sensitive to the phase $\textit{θ}$ , while the neutron EDM can provide bounds on the phase difference $\textit{θ}$ − $\textit{θ}$ . Therefore, they are complementary to each other in probing the CP phases of the $\textit{tcS}$ couplings.

China

Biao-Feng Hou

Xin-Qiang Li

Ya-Dong Yang

Xing-Bo Yuan

Ming-Wang Zhang

Phenomenological anatomy of top-quark FCNCs induced by a light scalar singlet

Quasi-Periodic Oscillations (QPOs) are an important phenomenon commonly observed in the X-ray radiation of black holes (BH) and neutron stars, closely related to the dynamics of accretion disks around Compact Objects (CO) and general relativistic effects. The objective of this study is to use the QPO phenomenon to distinguish between Dark Matter (DM)-BH systems and Naked Singularities (NS), as well as to investigate the effects of different dark matter models (Cold Dark Matter, CDM, and Scalar Field Dark Matter, SFDM) on the accretion disk dynamics. By introducing a DM correction model within the framework of general relativity, we systematically investigate the differences in dragging effects, characteristic frequency distribution, and the Innermost Stable Circular Orbit (ISCO) radius between DM-BH systems and NS, while analyzing the potential coupling between QPO frequencies and DM distribution. The main results of this study are as follows: In BH cases, the radial precession frequency $$\nu _r$$ is consistent with the High-Frequency QPO range only in the low-spin region ( $$a = 0.1 \sim 0.2$$ ); the vertical precession frequency $$\nu _\theta $$ matches the Low-Frequency QPO range around $$a = 0.5$$ , while the nodal precession frequency $$\nu _{\text {nod}}$$ agrees with the Low-Frequency QPO range around $$a = 0.7$$ , and exhibits frequency reversal in the high-spin region ( $$0.7< a < 1$$ ). NS cases, however, display markedly different characteristics: both radial and vertical precession frequencies show monotonic decrease with significant amplification, with $$\nu _r$$ reaching kHz levels at $$a = 1 \sim 1.2$$ , and $$\nu _\theta $$ reaching 700+ Hz at $$a = 1$$ , both far exceeding the QPO observational range; while the nodal precession frequency $$\nu _{\text {nod}}$$ remains consistently in the reverse state but with values falling within the High-Frequency QPO observational range. CDM and SFDM modulate the accretion disk dynamics at the order of $$10^{-6}$$ .

Zheng Ma

Zhaoyi Xu

Meirong Tang

Distinguishing between dark matter-black hole systems and naked singularities via quasi-periodic oscillations

We develop the pole-skipping structure in de Sitter (dS) spacetime and find that their leading frequencies satisfy the relation <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ω</mi><mrow><mi>d</mi><mi>S</mi></mrow></msub><mo>=</mo><mi>i</mi><mn>2</mn><mi>π</mi><msub><mi>T</mi><mrow><mi>d</mi><mi>S</mi></mrow></msub><mo stretchy="false">(</mo><mn>1</mn><mo>−</mo><mi>s</mi><mo stretchy="false">)</mo></math>, where <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>T</mi><mrow><mi>d</mi><mi>S</mi></mrow></msub><mo>=</mo><mn>1</mn><mo>/</mo><mn>2</mn><mi>π</mi><mi>L</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>s</mi></math> denotes spin. In the two-dimensional dS spacetime, the pole-skipping points near the cosmic horizon <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi><mo>=</mo><mi>L</mi></math> for the scalar field of spin 0 and the fermionic field of spin <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mfrac><mn>1</mn><mn>2</mn></mfrac></math> correspond one to one with those in the classical limit as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>λ</mi><mo stretchy="false">→</mo><mn>0</mn></math> in double-scaled Sachdev-Ye-Kitaev model when the temperature is infinite (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mrow><mi>DSSYK</mi></mrow><mi>∞</mi></msub></math>). This provides a numerical correspondence between quantum gravity in the static patch of two-dimensional dS spacetime and a one-dimensional quantum system, which we consider as a realization of the DS/dS correspondence.

Haiming Yuan

Xian-Hui Ge

South Korea

Keun-Young Kim

Pole skipping in two-dimensional de Sitter spacetime and double-scaled SYK model

Helicity selection rules can suppress the leading contributions from dimension-6 operators in the Standard Model effective field theory (SMEFT), reducing sensitivity to potential new physics. This paper explores how the interference contributions from the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>τ</mi></math> lepton’s anomalous dipole moment is restored in different observables, in particular comparing the sensitivity to SMEFT operators of quantum information observable and more traditional spin correlations. We compute the sensitivity of various observables—including entanglement measures, Bell inequality violations, and quantum uncertainties—to new physics effects using Monte Carlo simulations. Spin correlation observables are found to outperform both the integrated cross section and quantum information observables in sensitivity to both <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-conserving and -violating effects, improving the sensitivity to the scale of new physics by up to a factor of 3. Our results suggest that quantum information observables are suboptimal probes for resurrecting the interference, and more in general to disentangle the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> properties of new physics.

Germany

Prisco Lo Chiatto

Interference resurrection of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>τ</mi></mrow></math> dipole through quantum tomography

In this article, we probe the trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating (RPV) supersymmetric (SUSY) scenarios with specific nonzero interactions in the light of neutrino oscillation, Higgs, and flavor observables. We attempt to fit the set of observables using a state-of-the-art Markov Chain Monte Carlo (MCMC) setup and study its impact on the model parameter space. Our main objective is to constrain the trilinear couplings individually, along with some other SUSY parameters relevant to the observables. We present the constrained parameter regions in the form of marginalized posterior distributions on different two-dimensional parameter planes. We perform our analyses with two different scenarios characterized by our choices for the lightest SUSY particle (LSP), bino, and stop. Our results indicate that the lepton number violating trilinear couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>λ</mi><mrow><mi>i</mi><mn>33</mn></mrow></msub></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>i</mi><mo>=</mo><mn>1</mn></math>, 2) and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>λ</mi><mrow><mi>j</mi><mn>33</mn></mrow><mo>′</mo></msubsup></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>j</mi><mo>=</mo><mn>1</mn></math>, 2, 3) can be at most of the order of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math> or even smaller while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>tan</mi><mi>β</mi></math> is restricted to below 15 even when <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> allowed regions are considered. We further comment on the possible LHC signatures of these LSPs focusing on and around the best-fit regions.

Arghya Choudhury

Sourav Mitra

Arpita Mondal

Subhadeep Mondal

Markov chain Monte Carlo analysis to probe trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violating SUSY scenarios and possible LHC signatures