Our recent result on the construction of perfect fluid equations with <math altimg='si1.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn><mo>,</mo><mn>2</mn></mrow></math> Schr&#246;dinger supersymmetry [Mod. Phys. Lett. A 41 (2026) 2550214] is extended to accommodate nonrelativistic conformal supersymmetries of other types. Two cases are considered in detail, which include the <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math> conformal Newton-Hooke superalgebra and <math altimg='si3.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn></mrow></math> &#8467;-conformal Galilei superalgebra with arbitrary half-integer parameter &#8467;. Supersymmetric fluid models are built within the Hamiltonian framework by introducing real (for <math altimg='si3.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>1</mn></mrow></math>) or complex (for <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math>) anticommuting field variables as superpartners for the density and velocity. For both the cases the full set of conserved charges associated with the superalgebras is constructed and the Lagrangian description is given. Subtleties with the construction of perfect fluid equations with <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mn>2</mn></mrow></math> &#8467;-conformal Galilei supersymmetry are discussed as well.

Russia

Timofei Snegirev

Perfect fluid equations with nonrelativistic conformal supersymmetries

We investigate the structure of strange quark stars (SQSs) in the color–flavor–locked (CFL) phase in the presence of scalar bosonic dark matter within a two–fluid formalism. The quark matter equation of state (EOS) is obtained from perturbative QCD, incorporating the latest Particle Data Group values for the running coupling and strange quark mass, while the dark matter component is modeled as a self-interacting Bose–Einstein condensate. By considering different dark matter masses and varying the pairing gap Δ and the central dark matter pressure fraction <italic>f<inf>r</inf></italic>, we analyze the impact of dark matter on the structural properties of SQSs, including the maximum gravitational mass <italic>M</italic> <inf>TOV</inf>, the ratio of dark matter to strange-quark-matter radii <italic>R</italic> <inf>DM</inf>/ <italic>R</italic> <inf>SQM</inf>, and the dimensionless tidal deformability &#923;. We further examine the compatibility of the resulting mass&#8211;radius relations with the recent NICER measurements of compact stars. Within the parameter space considered in this study, we find that <italic>M</italic> <inf>TOV</inf> exhibits a non-monotonic dependence on the dark matter mass, with a critical value beyond which <italic>M</italic> <inf>TOV</inf> decreases. We also show that some pure CFL strange quark star configurations, particularly those associated with very stiff EOSs and larger maximum masses, may not simultaneously remain compatible with the &#923; range inferred from GW170817 while occupying the lower mass&#8211;gap region. In contrast, the inclusion of dark matter allows two-fluid CFL strange quark star configurations to reproduce the observed properties of massive compact objects in the lower mass&#8211;gap region, such as the secondary component of GW190814, while remaining qualitatively compatible with the &#923; range inferred from GW170817. We note, however, that the GW170817 constraints were originally inferred within single-fluid compact-star frameworks and therefore provide only qualitative guidance for the present two-fluid halo configurations. Our results suggest that exotic compact-star configurations may populate part of the conventionally defined lower mass&#8211;gap region.

Iran

J. Sedaghat

G.H. Bordbar

M. Haghighat

S.M. Zebarjad

Two–fluid CFL strange quark stars with scalar dark matter: Critical mass and mass–gap implications

We establish a new PBW basis for <math altimg='si1.svg'><msub><mi mathvariant='script'>A</mi><mi>q</mi></msub></math>, the alternating central extension of the <italic>q</italic>-Onsager algebra. Terwilliger showed that the alternating generators form a PBW basis in the block order <math altimg='si2.svg'><mrow><mi mathvariant='script'>G</mi><mo linebreak='goodbreak'>&lt;</mo><msup><mi mathvariant='script'>W</mi><mo>&#8722;</mo></msup><mo linebreak='goodbreak'>&lt;</mo><msup><mi mathvariant='script'>W</mi><mo>+</mo></msup><mo linebreak='goodbreak'>&lt;</mo><mover accent='true'><mrow><mi mathvariant='script'>G</mi></mrow><mo stretchy='true'>&#732;</mo></mover></mrow></math>. We prove that they also form a PBW basis in the different block order <math altimg='si3.svg'><mrow><msup><mi mathvariant='script'>W</mi><mo>&#8722;</mo></msup><mo linebreak='goodbreak'>&lt;</mo><mi mathvariant='script'>G</mi><mo linebreak='goodbreak'>&lt;</mo><mover accent='true'><mrow><mi mathvariant='script'>G</mi></mrow><mo stretchy='true'>&#732;</mo></mover><mo linebreak='goodbreak'>&lt;</mo><msup><mi mathvariant='script'>W</mi><mo>+</mo></msup></mrow></math>. Consequently, multiplication induces a vector-space isomorphism <display><formula id='ueq0001'><math altimg='si4.svg'><mrow><msup><mi mathvariant='script'>W</mi><mo>&#8722;</mo></msup><mi>&#8855;</mi><mi mathvariant='script'>G</mi><mi>&#8855;</mi><mover accent='true'><mrow><mi mathvariant='script'>G</mi></mrow><mo stretchy='true'>&#732;</mo></mover><mi>&#8855;</mi><msup><mi mathvariant='script'>W</mi><mo>+</mo></msup><mo>&#10230;</mo><msub><mi mathvariant='script'>A</mi><mi>q</mi></msub><mo>,</mo></mrow></math></formula></display>thereby confirming a conjecture of Terwilliger.

Singapore

Haoran Zhu

A new PBW basis for the alternating central extension of the <italic>q</italic>-Onsager algebra

Homogeneous and isotropic equilibrium states of strongly coupled <math altimg='si2.svg'><mrow><mi mathvariant='script'>N</mi><mo linebreak='goodbreak'>=</mo><mn>4</mn></mrow></math> supersymmetric Yang-Mills charged plasma in <math altimg='si3.svg'><msup><mrow><mi mathvariant='double-struck'>R</mi></mrow><mn>3</mn></msup></math> with equal chemical potentials for the maximal Abelian subgroup of the <italic>R</italic>-symmetry group become dynamically unstable below some critical temperature. The instabilities arise in the <italic>R</italic>-symmetry charge transport, precisely when the equilibrium state becomes thermodynamically unstable. We study the fate these correlated instabilities when the theory is placed on <italic>S</italic> 3. The curvature of the three-sphere affects the onset of the dynamical and the thermodynamic instabilities differently: increasing the curvature at low temperatures can stabilize its transport, but leave the plasma thermodynamically unstable. Thermodynamic stability is never recovered provided the <italic>S</italic> 3 volume is allowed to fluctuate. <math altimg='si2.svg'><mrow><mi mathvariant='script'>N</mi><mo linebreak='goodbreak'>=</mo><mn>4</mn></mrow></math> SYM is always thermodynamically unstable in the fixed-pressure ensemble on <italic>S</italic> 3 as well.

Canada

Alex Buchel

Instability in <math altimg='si2.svg'><mrow><mi mathvariant='script'>N</mi><mo linebreak='goodbreak'>=</mo><mn>4</mn></mrow></math> supersymmetric Yang-Mills theory on <italic>S</italic> 3 at finite density

In this work, two analytical solutions are proposed to characterize compact star configurations containing an effective negative-pressure fluid in the <italic>f</italic>( <italic>R, T</italic>) gravity paradigm that admit spherically symmetric geometry. We derive a system of modified field equations by taking into account a static interior spacetime, which consists of both negative-pressure fluid and ordinary matter sources. In order to investigate the interactions between the fluid components, we solve the field equations using two different equations of state. As the gravitational equations still contain more unknowns, we further use the Finch-Skea and Tolman IV spacetimes which lead us to two distinct models. The junction conditions are also applied to compute the constants associated with these solutions. Afterwards, our developed models&#8217; feasibility is explored by contrasting them with the observed characteristics of two particular stars, SAX J1808.4&#8211;3658 and Her X-1. Under certain parametric values, our results demonstrate that both the developed fluid configurations are physically realistic in this minimally coupled gravity framework.

Azerbaijan

Pakistan

M. Sharif

Tayyab Naseer

Aqsa Bashir

Examining the behavior of exotic compact stars within the <italic>f</italic>( <italic>R, T</italic>) gravity under Finch-Skea and Tolman IV spacetimes

We investigate an extended 3-4-1 model consisting of a new singly charged Higgs boson, implementing the minimal inverse seesaw mechanism to account for the current <math altimg='si61.svg'><msub><mrow><mo>(</mo><mi>g</mi><mo>&#8722;</mo><mn>2</mn><mo>)</mo></mrow><mrow><mi>e</mi><mo>,</mo><mi>&#956;</mi></mrow></msub></math> constraints as well as the lepton-flavor-violating decay rates of charged leptons, the Standard Model-like Higgs boson, and the <italic>Z</italic> boson, all consistent with current experimental data. Unlike the previously studied 3-4-1 realization, the model considered here predicts strong correlations among these observables that can be tested in future experiments. In particular, the current upper bound on Br( <italic>&#964;</italic>&#8239;&#8594;&#8239; <italic>&#956;&#947;</italic>) imposes a stringent constraint compatible with the 1 <italic>&#963;</italic> experimental range of <math altimg='si62.svg'><msub><mrow><mo>(</mo><mi>g</mi><mo>&#8722;</mo><mn>2</mn><mo>)</mo></mrow><mi>&#956;</mi></msub></math>, corresponding to an allowed deviation of order <math altimg='si30.svg'><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>9</mn></mrow></msup></math> from the SM prediction. The forthcoming experimental sensitivity to Br( <italic>&#964;</italic>&#8239;&#8594;&#8239; <italic>&#956;&#947;</italic>) will reduce this deviation to <math altimg='si63.svg'><mrow><mn>5</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>10</mn></mrow></msup></mrow></math>.

Vietnam

N.H.T. Nha

L.T. Hue

L.T.T. Phuong

T.T. Hong

LFV decays in a 3-4-1 model with minimal inverse seesaw neutrinos

In this study, the process <italic>&#947;&#947;</italic>&#8239;&#8594;&#8239; <italic>&#947;&#947;</italic> is investigated to establish constraints on anomalous Higgs boson couplings at <italic>H&#947;&#947;</italic> vertex within the framework of the Standard Model Effective Field Theory (SMEFT). The study is performed for a future muon collider operating at CoM energies of 10 and 30 TeV with integrated luminosities of 10 and 90 ab <math altimg='si9.svg'><msup><mrow /><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></math>, respectively, where the incoming photons are modeled using the Weizs&#228;cker-Williams approximation. Signal and background events are simulated using MadGraph, with the SMEFT Lagrangian implemented via FeynRules and UFO frameworks. Parton showering is evaluated with PYTHIA 8, and detector effects are accounted for using Delphes. Limits on the Wilson coefficients <math altimg='si5.svg'><msub><mover accent='true'><mi>c</mi><mo>&#175;</mo></mover><mi>&#947;</mi></msub></math> and <math altimg='si1.svg'><msub><mover accent='true'><mi>c</mi><mo>&#732;</mo></mover><mi>&#947;</mi></msub></math> of the dim-6 operators without and with systematic uncertainties of 5% and 10% are reported at the 95% confidence level, demonstrating the potential of a high-energy muon collider to provide precise constraints on these couplings and presenting a significant improvement over experimental and related phenomenological results.

Türkiye

Serdar Spor

Emre Gurkanli

Analysis of anomalous <italic>H&#947;&#947;</italic> coupling in light-by-light collision at future muon collider

We investigate the vacuum expectation value of the bosonic current induced by a magnetic flux in a <math altimg='si12.svg'><mrow><mo>(</mo><mn>2</mn><mo linebreak='goodbreak'>+</mo><mn>1</mn><mo>)</mo></mrow></math>-dimensional conical spacetime in the presence of a circular boundary within a Ho&#345;ava-Lifshitz Lorentz-violating scenario. The circular boundary is assumed to be concentric with the magnetic flux, and the massive scalar field is taken to satisfy Robin boundary conditions on it. To carry out the analysis, we construct the positive-frequency Wightman functions in both regions, namely, inside and outside the circular boundary. Using these functions, we derive analytical expressions for the corresponding vacuum currents. We show that the Wightman functions, as well as the induced currents, can be naturally decomposed into boundary-free and boundary-induced contributions. For the boundary-induced current, several asymptotic behaviors are examined in relevant limiting cases. In addition, numerical results are presented in order to provide a clearer understanding of the dependence of the induced currents on the parameters of the model.

Brazil

E.R. Bezerra de Mello

H.F. Santana Mota

Induced current by a magnetic flux in <math altimg='si11.svg'><mrow><mo>(</mo><mn>1</mn><mo linebreak='goodbreak'>+</mo><mn>2</mn><mo>)</mo><mo>&#8722;</mo></mrow></math>dimensional conical spacetime in a Ho&#345;ava-Lifshitz Lorentz-violating scenario

We study equatorial timelike geodesics and high-frequency quasi-periodic oscillations (HF QPOs) in the spacetime of a non-minimally coupled Horndeski black hole belonging to the quartic square-root sector of the theory. Starting from the geodesic equations, we derive the specific energy, specific angular momentum, effective potential, and the characteristic frequencies governing circular motion. We then determine the innermost stable circular orbit (ISCO) together with the Keplerian, radial, and vertical epicyclic frequencies, and we quantify their dependence on the Horndeski parameters <italic>&#951;</italic> and <italic>&#946;</italic>. We show that the non-minimal coupling shifts the binding properties of circular orbits, displaces the ISCO, and modifies the epicyclic-frequency structure relevant to QPO phenomenology. Owing to spherical symmetry, the vertical epicyclic frequency coincides with the orbital one, whereas the radial epicyclic mode vanishes at the ISCO and develops a maximum at larger radii. Using the ER, ER1, ER3, and ER4 resonance prescriptions, we map these frequency shifts into the observable HF QPO plane and compare the model phenomenologically with the microquasar sources GRO J1655&#8211;40, XTE J1550&#8211;564, XTE J1859+226, GRS 1915+105, and H1743&#8211;322. In addition, for GRS 1915+105 and XTE J1550&#8211;564&#8212;the two systems for which full posterior results are presented in this manuscript&#8212;we perform a Markov Chain Monte Carlo analysis to constrain the parameter combinations ( <italic>M, &#951;, &#946;, r</italic>) favored by the observed QPO pairs. Our results show that HF QPO measurements can place nontrivial constraints on non-minimally coupled Horndeski black holes and provide a useful probe of strong-field deviations from general relativity.

Uzbekistan

China

Ziyodulla Turakhonov

Husanboy Hoshimov

Akbar Davlataliev

Farruh Atamurotov

Ahmadjon Abdujabbarov

Chengxun Yuan

Particle dynamics and quasi-periodic oscillations in the non-minimally coupled Horndeski black hole

String axiverse provides a fascinating and complex landscape for axion physics. The requirement in type IIB string axiverse models necessitates at least two axions to ensure the presence of both a QCD axion candidate and an additional axion-like particle (ALP). In this work, we study axion mass mixing and adopt a bottom-up perspective to investigate what conditions an axion model must satisfy in order to exhibit maximal mixing — the scenario where the degree of effective mixing is maximized. We find that maximal mixing occurs when the masses of all ALPs are smaller than the zero-temperature mass of the QCD axion, with no two ALP masses being equal, and when the decay constants of all ALPs are uniformly either smaller or larger than the decay constant of the QCD axion. Additionally, the transfer of axion energy density ultimately takes place only between the two axions with the closest masses. These findings provide critical insights into axion dynamics not only within type IIB string axiverse models but also in broader multi-axion mixing frameworks. The potential cosmological implications of axion mass mixing are also addressed at the end.

Hai-Jun Li

Yu-Feng Zhou

Axion mixing in the string axiverse