Hyperon-antihyperon pairs produced in high-energy electron-positron annihilation constitute a naturally spin-entangled system in the high-energy regime. Recently, a probabilistic amplification of entanglement, termed autodistillation, has been found in the daughter baryon-antibaryon pairs from hyperon decay and is constrained by an upper boundary. This work demonstrates that the quantum entanglement in this process may be accompanied by a decrease, constrained by a lower boundary, but it will not be completely lost. Thus, the entanglement of these systems undergoes redistribution within the phase space during the sequential decays of hyperons, highlighting the important role of hyperon polarization. By using the explicit spin density matrix of baryon pairs, it is also found that the quantumness of the system, characterized by quantum discord, always has the possibility to increase during decay processes, even when entanglement evaluated by concurrence and negativity does not increase.

China

Cong Li

Xu Cao

Ai-Qiang Guo

Chun-Xu Yu

Hong-Wei Zhang

Zhe Zhang

Entanglement redistribution of hyperon-antihyperon pair via sequential decay * Supported by the National Natural Science Foundation of China (12547111, 12447132, 12575089) and the National Key R&D Program of China (2023YFA1606703)

A search for the decay $ B^+\to D_s^+ K^+K^- $ has been reported by the LHCb Collaboration using $ pp $ collision data corresponding to an integrated luminosity of $4.8\;{\rm{fb}}^{-1}$ , collected at center-of-mass energies of 7, 8, and 13 TeV, in which no amplitude analysis of the $ K^+K^- $ subsystem was performed. In this work, we study the resonant contributions to the decay $ B^+\to D_s^+ K^+K^- $ within the perturbative QCD (PQCD) factorization framework. Contributions from the $\textit{S}$-wave resonances $ f_0(980) $ , $ f_0(1370) $ , and $ f_0(1500) $ , the $\textit{P}$-wave resonance $ \phi(1020) $ , and the $\textit{D}$-wave resonances $ f_2(1270) $ and $ f_2(1525) $ are taken into account. By introducing the corresponding two-meson distribution amplitudes for the $ K^+K^- $ system, we perform a complete perturbative analysis of the quasi-two-body decays $ B^+\to D_s^+(R\to)K^+K^- $ , where $\textit{R}$ denotes an intermediate resonance, and present the first PQCD predictions for the associated branching fractions. Using the narrow-width approximation, we further extract the branching fractions of the corresponding two-body decays $ B^+\to D_s^+R $ . Our results are consistent with the available experimental measurements and previous theoretical studies. Finally, we find that direct CP asymmetries vanish for these quasi-two-body decays within the Standard Model, so that any experimentally observed nonzero CP asymmetry would constitute a clear signal of physics beyond the Standard Model.

Zhi-Tian Zou

Jun-Peng Wang

Rui Zhou

Ying Li

Quasi-two-body decays $ {B^+\to D_s^+ (R\to) K^+K^-} $ in the perturbative QCD approach * Supported in part by the National Science Foundation of China (12375089, 12435004, 12075086), and the Natural Science Foundation of Shandong province (ZR2022ZD26, ZR2022MA035)

In this paper we analyze the optical appearance of black holes embedded in a cosmological background in some popular <italic>f</italic>( <italic>R</italic>) models which are often considered as viable alternatives to the &#923;CDM model in General Relativity. After obtaining analytical approximations for the Hubble rate <italic>H</italic>( <italic>z</italic>) and angular diameter distance <italic>d<inf>A</inf></italic>( <italic>z</italic>), we compute the approximate shadow size for a spherically symmetric black hole embedded in these <italic>f</italic>( <italic>R</italic>) models as viewed by a comoving observer located very far from the black hole. This is then compared with the shadow size of a black hole embedded in the &#923;CDM model as obtained recently in Bisnovatyi-Kogan &amp; Tsupko (PRD <bold>98</bold>, 084,020 (2018)). Differences in the shadow size for cosmological black holes between <italic>f</italic>( <italic>R</italic>) gravity and General Relativity are discussed in light of the recent observations by the EHT collaboration.

Malta

Joseph Sultana

Optical appearance of cosmological black holes in <italic>f</italic>( <italic>R</italic>) gravity

We numerically investigate the time evolution of several physical observables for the so-called 2 R-Charge Black Hole (2RCBH) model undergoing Bjorken flow. The 2RCBH model corresponds to a top-down holographic construction describing a strongly interacting conformal fluid defined at finite temperature and R-charge density. Taken together with previous findings for the purely thermal $$\mathcal {N}=4$$ Supersymmetric Yang–Mills (SYM) plasma, and the 1 R-Charge Black Hole (1RCBH) model, our results for the 2RCBH model provide strong numerical evidence for the existence of far-from-equilibrium correlations between the non-equilibrium holographic entropy defined through the area of the apparent horizon of dynamical bulk black holes, and the expectation value of the energy–momentum tensor of the dual boundary quantum field theory. Such correlations are relevant in the pre-hydrodynamic stages of some initial data evolved in time, and seem to hold at least for strongly interacting conformal fluids, be they charged or neutral.

Brazil

Gustavo Oliveira

Venezuela

Willians Barreto

Romulo Rougemont

Bjorken flow of holographic R-charged plasmas

An intermediate scale R-axion faces an immediate obstruction from the Dine-Festuccia-Komargodski (DFK) bound on the superpotential, 2|⟨$\textit{W}$⟩| ≤ $\textit{f}$ $\textit{F}$, since for a nearly Minkowski vacuum it typically follows that $\textit{f}$ ≳ $\textit{M}$ . We show that this lower bound on $\textit{f}$ can be relaxed in an effective construction with the scalar potential tuned near zero via a mixed $\textit{F}$- and $\textit{D}$-term uplift, leading to a metastable vacuum in which the usual Planckian-$\textit{f}$ inference from the DFK argument is avoided locally. Validity of the effective field theory and metastability of the small $\textit{f}$ vacuum generically both imply a relaxed bound: $$ {f}_R\gtrsim \sqrt{m_{3/2}{M}_{\mathrm{Pl}}} $$ . We also highlight that if the R-symmetry has a QCD anomaly, this potentially permits the R-axion to play the role of the QCD axion. TeV-scale supersymmetry permits $\textit{f}$ ~ 10 GeV, this not only evades certain astrophysical and cosmological axion constraints, but notably lies in the window for which the observed dark matter abundance can be reproduced by the R-axion via the misalignment mechanism.

United States

James Unwin

An intermediate scale R-axion & the QCD axion

The persistent 4–6 <italic>&#963;</italic> Hubble tension between Planck and SH0ES measurements challenges the standard &#923;CDM framework. We propose a solution combining generalized inhomogeneous spacetime geometry with Hu-Sawicki <italic>F</italic>( <italic>R</italic>) gravity. Using a spherically symmetric metric with independent functions <italic>A</italic>( <italic>t, r</italic>) and <italic>B</italic>( <italic>t, r</italic>), we show that local underdensities with modified gravity produce a &#8220;Hubble bubble&#8221; effect while maintaining global CMB consistency. Bayesian analysis incorporating SH0ES, Pantheon+, BAO, and cosmic chronometers yields <math altimg='si1.svg'><mrow><msubsup><mi>H</mi><mn>0</mn><mtext>local</mtext></msubsup><mo linebreak='goodbreak'>=</mo><mn>72.76</mn><mo>&#177;</mo><mn>1.18</mn></mrow></math> km/s/Mpc and <math altimg='si2.svg'><mrow><msubsup><mi>H</mi><mn>0</mn><mtext>global</mtext></msubsup><mo linebreak='goodbreak'>=</mo><mn>68.18</mn><mo>&#177;</mo><mn>0.76</mn></mrow></math> km/s/Mpc, reconciling the tension. The model achieves this through enhanced gravitational forces in underdense regions, chameleon screening preserving Solar System tests, and consistent structure formation. With <math altimg='si25.svg'><mrow><mi>ln</mi><mi>B</mi><mo linebreak='goodbreak'>=</mo><mn>2.28</mn><mo>&#177;</mo><mn>0.39</mn></mrow></math> favoring our model over &#923;CDM, we present compelling evidence for the interplay between local inhomogeneities and modified gravity as the origin of the Hubble tension.

Pakistan

 Mehnaz

Azerbaijan

Jordan

Adnan Malik

Jamshed Khan

Saudi Arabia

Ahdab K. Althukair

Resolving the hubble tension: A unified approach using inhomogeneous Hu-Sawicki <italic>F</italic>( <italic>R</italic>) gravity

We study the local horizon residue and minimally coupled massless-scalar quasinormal modes of the logarithmic connection-hair background obtained perturbatively in the quadratic model $$f(Q)=Q+\alpha Q^2$$ . After mass renormalization the displayed order- $$\alpha ^2$$ blackening function is $$F(r)=1-[2M+\eta \ln (r/r_\star )]/r$$ , with $$\eta =\alpha ^2\mu $$ . Euclidean regularity and the simple pole of 1/$\textit{F}$ give the same Hawking temperature, while the same residue multiplies the near-horizon logarithm of the scalar tortoise coordinate. We derive the massless-scalar master equation, its effective potential, the photon-sphere equation, and the controlled first-order shifts of the eikonal scalar frequency and damping rate. We do not identify the integration parameter $\textit{M}$ with a Hamiltonian or Noether mass: the logarithmic tail leaves the perturbative regime at large radius and does not satisfy the standard falloff required for a finite ADM charge. Consequently no physical entropy, heat capacity, Ruppeiner metric, or gravitational quasinormal-mode spectrum is claimed. For comparison only, we retain an explicitly labelled auxiliary Hessian construction and an algebraic evaluation of the resummed truncated metric at $$r_h=2\eta $$ . That point has $$|\eta |/r_h=1/2$$ and is therefore outside perturbative control; its finite scalar null-orbit and WKB frequencies are properties of the truncated function, not predictions of quadratic $\textit{f}$($\textit{Q}$) gravity. The controlled result is the local temperature–scalar-monodromy residue identity and the distinct small-hair shifts sampled at the horizon and photon sphere.

Wen-Xiang Chen

Horizon residues and test-scalar quasinormal modes of a perturbative Schwarzschild-type black hole in quadratic $\textit{f}$($\textit{Q}$) gravity

In holography, the complexity-momentum correspondence relates the increasing momentum of a point particle falling into an eternal black hole to the rate of growth of the Krylov complexity of the dual boundary state, a conjecture established exactly for the BTZ black hole in AdS at the semiclassical level. We examine possible extensions of the correspondence by considering boundary higher Krylov complexities and Krylov correlators encoding fluctuations and temporal correlations of the spreading quantum state. To this end, we derive exact results for Krylov correlators in quantum systems with $$ \mathfrak{sl}\left(2,\mathbb{R}\right) $$ or Heisenberg-Weyl symmetry and apply them to the complexity-momentum correspondence. We show that certain out-of-time-ordered correlators of two or more Krylov speed operators at different times are proportional to combinations of the proper radial momenta of a particle falling into the BTZ black hole in AdS , evaluated at those times. This represents a first step in the generalization of the original complexity-momentum relation.

Italy

E. Alfinito

M. Beccaria

Krylov correlators in $$ \mathfrak{sl}\left(2,\mathbb{R}\right) $$ models: exact results and holographic complexity

We consider $$R^2$$ gravity cosmological models with radiation. We find the general solution to the trace equation $$\Box R=0$$ in the spatially flat Friedmann–Lemaitre–Robertson–Walker (FLRW) metric. We analyze possible evolution of the Hubble parameter depending on the sign of the radiation energy density and find conditions for the existence of a bounce solution. A scalar field Lagrangian with the induced gravity term and the fourth-order monomial potential can play a role of radiation. In this case, we also obtain the general solution to the field equation. Therefore, the resulting $$R^2$$ gravity model with a scalar field is integrable in the spatially flat FLRW metric. Using a conformal metric transformation, we obtain a two-field chiral cosmological model that is also integrable in the spatially flat FLRW metric.

Russia

Vsevolod Ivanov

Sergey Vernov

Integrability of $$R^2$$ gravity cosmological models with radiation

The <italic>f</italic>( <italic>R, T, Y</italic>) gravity is a modified theory that involves the Ricci scalar <italic>R</italic>, the trace of the energy-momentum tensor <italic>T</italic>, and the non-minimal matter geometry coupling term <math altimg='si3.svg'><mrow><mi>Y</mi><mo linebreak='goodbreak'>=</mo><msub><mi>R</mi><mrow><mi>a</mi><mi>b</mi></mrow></msub><msup><mi>T</mi><mrow><mi>a</mi><mi>b</mi></mrow></msup></mrow></math>. In this article, we are eager to explore the imprints of <italic>f</italic>( <italic>R, T, Y</italic>) cosmology on the early universe through the observational constraints of Big Bang nucleosynthesis. To analyze the early universe scenario, we investigate the deviation of freeze-out temperature through the ratio <math altimg='si1.svg'><mrow><mrow><mo>|</mo><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle></mrow><msub><mi mathvariant='script'>T</mi><mi>f</mi></msub><mo linebreak='goodbreak'>/</mo><msub><mi mathvariant='script'>T</mi><mi>f</mi></msub><mrow><mo>|</mo></mrow></mrow></math> that has observation limits <math altimg='si4.svg'><mrow><mrow><mo>|</mo><mstyle mathvariant='normal'><mi>&#916;</mi></mstyle></mrow><msub><mi mathvariant='script'>T</mi><mi>f</mi></msub><mo linebreak='goodbreak'>/</mo><msub><mi mathvariant='script'>T</mi><mi>f</mi></msub><mrow><mo>|</mo><mo>&#8804;</mo><mn>4.7</mn><mo linebreak='badbreak'>&#215;</mo></mrow><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msup></mrow></math> and the primordial helium mass fraction <italic>Y<inf>p</inf></italic> of the light nuclear species having observational limits <math altimg='si5.svg'><mrow><msub><mi>Y</mi><mi>p</mi></msub><mo linebreak='goodbreak'>=</mo><mn>0.245</mn><mo>&#177;</mo><mn>0.003</mn></mrow></math>. For instance, we consider two models <math altimg='si6.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>,</mo><mi>Y</mi><mo>)</mo><mo>=</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><mi>&#945;</mi><mi>Y</mi></mrow></math> and <math altimg='si7.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo>,</mo><mi>Y</mi><mo>)</mo><mo>=</mo><mi>R</mi><mo linebreak='goodbreak'>+</mo><mi>&#945;</mi><mi>Y</mi><mo linebreak='goodbreak'>+</mo><mi>&#947;</mi><mi>T</mi></mrow></math> to evaluate the viability of observational limits. We analyzed these models for the radiation-dominated era ( <math altimg='si8.svg'><mrow><mi>&#961;</mi><mo linebreak='goodbreak'>=</mo><mn>3</mn><mi>p</mi></mrow></math>) in the early universe. Our findings indicate that <italic>f</italic>( <italic>R, T, Y</italic>) gravity can agree with recent observational bounds on big bang nucleosynthesis via deviations in freeze-out temperature and primordial helium abundances, leading to a viable cosmology in the early cosmic epoch.

Abdul Malik Sultan

Ibrahim Aldayel

Kainat Naseer

Manahil Ali

Meraj Ali Khan

Abdul Jawad

Observational signatures of <italic>f</italic>( <italic>R, T, Y</italic>) gravity on early universe evolution