Multiple lattice evidences support the existence of a confining but chirally symmetric stringy fluid regime of QCD above the chiral symmetry restoration temperature at <italic>T<inf>ch</inf></italic>&#8239;&#8771;&#8239;155 MeV. This regime is characterized by an approximate chiral spin symmetry and its extensions which means that the propagating excitations represent the chirally symmetric quarks connected into color singlets by the chromoelectric string. Clear <italic>&#960;, &#960;</italic>&#8242; peaks above <italic>T<inf>ch</inf></italic> were extracted on the lattice from the spatial and temporal correlators, which become broader with temperature and disappear roughly at 3 <italic>T<inf>ch</inf></italic>. The meson-like excitations above <italic>T<inf>ch</inf></italic> were studied within the manifestly confining and chirally symmetric model. It has been demonstrated that the chiral symmetry restoration in the confining regime happens because of Pauli blocking of the levels, required for the existence of the quark condensate, by the thermal quark excitation. The same Pauli blocking leads to a huge swelling of the low-spin mesons above <italic>T<inf>ch</inf></italic> which become infinitely large in the chiral limit. This property should be crucial for the explanation of the high collectivity and a very small mean-free path of the constituents above <italic>T<inf>ch</inf></italic> seen experimentally. Here we demonstrate that the swelling of pions above <italic>T<inf>ch</inf></italic> is a model-independent effect required by current algebra.

Austria

L. Ya. Glozman

A large size of the pion-like excitations in the stringy fluid above <italic>T<inf>ch</inf></italic> is model independent and required by current algebra

We construct and analyze static multipolar black holes in Einstein-vector-Gauss-Bonnet theory with a quadratic coupling function. The vectorized solutions bifurcate from the Schwarzschild black hole at discrete values of the Gauss-Bonnet coupling, obtained from a perturbative eigenvalue problem on the Schwarzschild background and labelled by the angular multipole number ℓ. We restrict to the fundamental radial branches. The electric sector contains the known spherically symmetric <math altimg='si3.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><mn>0</mn></mrow></math> branch as well as axisymmetric branches with &#8467;&#8239;&gt;&#8239;0. These electric branches extend to larger values of the coupling. The magnetic sector features a sequence of axisymmetric branches, including the previously found magnetic dipole branch at <math altimg='si3.svg'><mrow><mi>&#8467;</mi><mo linebreak='goodbreak'>=</mo><mn>0</mn></mrow></math>. The magnetic branches instead exist only on finite intervals of the coupling, ending at critical solutions. Away from the bifurcation point, nonlinearities generate additional multipoles, but even-&#8467; and odd-&#8467; moments remain separated.

Germany

Burkhard Kleihaus

Jutta Kunz

Static multipolar Einstein-vector-Gauss-Bonnet black holes

The QCD trace anomaly is a well-established textbook result in quantum field theory with several prominent features: (1) it arises from the quantum breaking of scale symmetry at ultraviolet (UV) scales, yet its full renormalized expression is independent of the particular UV regulator used, whether lattice or dimensional regularization; (2) although nominally of order <italic>&#945;<inf>s</inf></italic>, it is free of renormalization-scheme ambiguity; and (3) it is free of UV divergences and therefore scale independent. We show that renormalization in a reducible operator basis introduces additional convention dependence in its separation into quark and gluon parts, which do not share the properties of the whole anomaly itself. An irreducible decomposition instead keeps the trace anomaly as a single, convention-free component, and gives transparent physical meanings to anomaly-related nucleon physics, including the nucleon mass structure and internal forces.

United States

Chen Yang

Physics of the QCD trace anomaly and renormalization in a reducible basis

No-boundary instantons and Euclidean “wineglass” wormholes have both been proposed as providing suitable initial conditions for the current expanding phase of our universe, and in particular for providing conditions that are favorable to an inflationary phase. These finite action solutions have generally been regarded as unrelated, and enacting different scenarios – in one case the creation of spacetime from nothing, and in the other up-tunneling from an Anti-de Sitter vacuum. By studying explicit solutions of both axionic and magnetic wineglass wormholes, we find that in the zero-charge limit the throat of the wormholes pinches off, leaving a no-boundary instanton that disconnects from the asymptotic Anti-de Sitter region. Thus wormholes and no-boundary instantons are part of a common family of Euclidean solutions. Along the way, we resolve the long-known puzzle that the action of wineglass wormholes can become negative. Moreover, small-charge wormholes lead to a longer inflationary phase than large-charge solutions, while no-boundary instantons dominate the probability distribution overall.

Georgia

George Lavrelashvili

Jean-Luc Lehners

Nucleating an inflationary universe: Euclidean wormholes and their no-boundary limit

We study kinematical properties of the process <math altimg='si14.svg'><mrow><msup><mi>l</mi><mo>&#8722;</mo></msup><msup><mi>l</mi><mo>+</mo></msup><mo>&#8594;</mo><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>Z</mi><mi>h</mi></mrow></math> at future TeV-scale lepton colliders. We classify the Feynman amplitudes into three main topological categories: vector-boson scattering, <math altimg='si15.svg'><mrow><msup><mi>l</mi><mo>&#8722;</mo></msup><msup><mi>W</mi><mo>+</mo></msup></mrow></math> scattering, and <math altimg='si16.svg'><mrow><msup><mi>W</mi><mo>&#8722;</mo></msup><msup><mi>l</mi><mo>+</mo></msup></mrow></math> scattering contributions, and analyze the interference patterns among these amplitudes in both the recently proposed Feynman-diagram (FD) gauge and the conventional unitary gauge. We demonstrate that the rapidity distributions of the <italic>Z</italic> boson closely resemble those in <math altimg='si17.svg'><mrow><msup><mi>l</mi><mo>&#8722;</mo></msup><msup><mi>l</mi><mo>+</mo></msup><mo>&#8594;</mo><mi>&#957;</mi><mover accent='true'><mi>&#957;</mi><mo>&#175;</mo></mover><mi>Z</mi></mrow></math>, while the Higgs-boson rapidity distribution is significantly different: Higgs bosons are produced nearly isotropically, whereas longitudinally polarized <italic>Z</italic> bosons are enhanced in the forward and backward regions. We find that this difference is traced to the topology-dependent structure of the FD-gauge amplitudes. We also demonstrate that suitable kinematical cuts can isolate specific subamplitudes, enabling partial FD-gauge amplitudes to effectively describe physical distributions.

Japan

Hiroyuki Furusato

Satsuki Hosoya

Kentarou Mawatari

Shouta Suzuki

Higgs production in association with a Z boson at TeV-scale lepton colliders

We investigate the Dynamical Casimir Effect (DCE) for a relativistic scalar field confined within a cavity possessing moving boundaries in the (1+1)-dimensional near-horizon geometry of a black hole. By applying a coordinate transformation, we map the moving-boundary problem to an equivalent acoustic metric with static boundaries, allowing for an exact canonical Hamiltonian formulation. We find that the local gravitational redshift fundamentally alters the vacuum structure, and the dynamical boundary motion induces time-dependent mode-mixing. When a boundary moves, it scatters the fluctuations of the ambient Hartle-Hawking state, generating excitations within the cavity. For sinusoidal motion, we choose a small fixed fractional amplitude and impose the timelike-wall condition. When the drive tracks the resonant sum of fixed mode numbers, the effective Mach number approaches zero as the optical length increases. At leading perturbative order and over a fixed Killing-time interval of the specified drive, the vacuum transition probability for a fixed pair scales as <math altimg='si1.svg'><msubsup><mi>D</mi><mn>0</mn><mrow><mo>&#8722;</mo><mn>4</mn></mrow></msubsup></math>, where <math altimg='si2.svg'><mrow><msub><mi>D</mi><mn>0</mn></msub><mo linebreak='goodbreak'>=</mo><mi>ln</mi><mrow><mo>(</mo><mi>g</mi><mo linebreak='badbreak'>/</mo><msub><mi>f</mi><mn>0</mn></msub><mo>)</mo></mrow></mrow></math>. Furthermore, we account for the Bose-enhancement caused by the thermal Hawking bath. The net mean pair yield, after subtracting inverse absorption, scales as <math altimg='si3.svg'><msubsup><mi>D</mi><mn>0</mn><mrow><mo>&#8722;</mo><mn>3</mn></mrow></msubsup></math> for the same fixed pair and driving interval. These scalings depend on the driving protocol and do not establish a universal suppression of particle creation for arbitrary timelike trajectories or for the full three-dimensional field.

Iran

H. Hadi

Türkiye

Amin Rezaei Akbarieh

Göksel Daylan Esmer

Dynamical Casimir Effect and vacuum friction in the near-horizon geometry of a black hole

The pair transverse momentum ( <italic>k<inf>T</inf></italic>) and collision-energy ( <math altimg='si7.svg'><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math>) dependent difference between <math altimg='si3.svg'><mrow><msup><mi>&#960;</mi><mo>+</mo></msup><msup><mi>&#960;</mi><mo>+</mo></msup></mrow></math> and <math altimg='si4.svg'><mrow><msup><mi>&#960;</mi><mo>&#8722;</mo></msup><msup><mi>&#960;</mi><mo>&#8722;</mo></msup></mrow></math> femtoscopic correlations was observed by the HADES and STAR Collaborations. We investigate how much of the observed splitting can be accounted for by Coulomb dynamics in 0&#8211;10% central Au+Au collisions at <math altimg='si2.svg'><mrow><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt><mo linebreak='goodbreak'>=</mo><mn>2.42</mn></mrow></math>&#8211;5.2&#8239;GeV. Using the UrQMD model and the CRAB programme, three transport scenarios that successively include baryon&#8211;baryon, baryon&#8211;meson, and meson&#8211;meson Coulomb interactions are considered. In a separate calculation based on the baryon&#8211;baryon reference, we reconstruct the time-dependent effective charge <italic>Z</italic> <inf>eff</inf>( <italic>t</italic>) and radius <italic>R</italic> <inf>eff</inf>( <italic>t</italic>) of the residual charged source and propagate each pion from its individual last strong-interaction point through the evolving field. The calculations reproduce the main <italic>k<inf>T</inf></italic> and <math altimg='si7.svg'><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math> dependences of the radii. Baryon&#8211;meson Coulomb interactions generate most of the additional charge splitting in the microscopic calculation. The residual-source treatment also enhances the longitudinal and sideward radius ratios relative to the reference, whereas the outward ratio changes little, and the enhancement generally decreases with increasing <math altimg='si7.svg'><msqrt><msub><mi>s</mi><mrow><mi>N</mi><mi>N</mi></mrow></msub></msqrt></math>. Within the present framework, this contribution does not fully account for the data, motivating further investigation of the charged-source geometry and its interplay with strong-interaction dynamics.

China

Russia

Pengcheng Li

Yongjia Wang

Qingfeng Li

Dynamical Coulomb effects on charged-pion HBT-radius splitting in central Au+Au collisions at few-GeV energies

Wigner- and mirror-correlated kernel ridge regression (WKRR) and its odd-even extension WKRRoe are developed to improve nuclear mass predictions. The Wigner and mirror correlations are encoded entirely in the kernel functions without introducing more weight parameters. For experimentally known nuclear masses, WKRRoe achieves a leave-one-out root-mean-square deviation of 98.0 keV, which falls below the often-quoted 100-keV scale discussed in connection with chaos-related limits. The gain is mainly concentrated in light nuclei near <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mi>Z</mi></mrow></math> and is especially large for mirror pairs. Further tests show that WKRRoe can potentially improve predictions for experimentally unknown nuclei near <math altimg='si2.svg'><mrow><mi>N</mi><mo linebreak='goodbreak'>=</mo><mi>Z</mi></mrow></math>, particularly when their mirror partners have already been measured.

X.H. Wu

Wigner and mirror correlations in nuclear mass predictions with kernel ridge regression

Einstein-cluster dark matter halos have zero radial pressure in the ideal static model. I test whether this property survives the exact finite-spin ACKN/KSZ rotating continuation, whose geodesic and scalar-wave equations are separable. Using the full metric, I require <math altimg='si12.svg'><mrow><msub><mi>p</mi><mi>r</mi></msub><mo linebreak='goodbreak'>=</mo><mn>0</mn></mrow></math> at every polar angle. The condition factorizes and leaves only flat or Schwarzschild seeds. Their rotating members are flat space or Kerr. Thus, a nonvacuum Einstein-cluster seed cannot remain radially pressureless in this class. If the same nonvacuum seed is kept, the rotating metric instead generates a negative radial principal stress, with leading behavior <italic>O</italic>( <italic>a</italic> <sup>2</sup>). For a relativistic Hernquist halo, I evaluate the ratio | <italic>p<inf>r</inf></italic>|/ <italic>&#961;<inf>h</inf></italic> exactly at <math altimg='si3.svg'><mrow><mi>r</mi><mo linebreak='goodbreak'>=</mo><mn>10</mn><mi>M</mi></mrow></math> and <math altimg='si1.svg'><mrow><mi>a</mi><mo linebreak='goodbreak'>/</mo><mi>M</mi><mo linebreak='goodbreak'>=</mo><mn>0.3</mn></mrow></math>. The three published benchmarks give <math altimg='si13.svg'><mrow><mn>2.36</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>3</mn></mrow></msup></mrow></math>, <math altimg='si14.svg'><mrow><mn>2.27</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>2</mn></mrow></msup></mrow></math>, and <math altimg='si15.svg'><mrow><mn>1.23</mn><mo linebreak='goodbreak'>&#215;</mo><msup><mn>10</mn><mrow><mo>&#8722;</mo><mn>1</mn></mrow></msup></mrow></math>. The weak-halo estimate underpredicts the first two values by about 50%. Therefore, in the ACKN/KSZ class, preserving separability does not preserve the ideal Einstein-cluster matter source.

Chile

Mohsen Fathi

Radial stress in rotating ACKN/KSZ continuations of Einstein-cluster dark matter halos

We study the closed-to-open transition of bosonic strings in the tensionless regime in the presence of a constant Kalb-Ramond field. The intrinsically tensionless action yields a mixed boundary condition which, in the closed-string channel, becomes a universal gluing relation between the two oscillator sectors. The associated mode-independent gluing matrix deforms Neumann gluing, and the induced vacuum is an explicit squeezed boundary state. A background-dependent Bogoliubov transformation shows how this state is reached from the tensile closed-string vacuum. For toroidal compactification the Kalb-Ramond field shifts the momentum-winding lattice but leaves the level-matched Bose-Einstein-like condensation channel unchanged. We also give a boundary symplectic derivation of endpoint noncommutativity. In the tensile theory it reproduces the Seiberg-Witten tensor, whereas in the tensionless theory the first-order Kalb-Ramond coupling is the sole surviving contribution to the boundary symplectic structure. Its inverse therefore determines the intrinsic endpoint noncommutativity of the tensionless open string.

Sarthak Duary

India

Sourav Maji

From closed to open strings: The tensionless route in Kalb-Ramond background and noncommutativity