We ask whether two classical time-machine geometries, the Ori (2005) compact-vacuum-core metric and the Ahmed (2018) four-dimensional generalisation of Misner space, remain admissible exact solutions when the gravitational sector is enlarged to the recently proposed $$f(R,\mathcal {L}_{m},\Phi ,X)$$ class, an extension of $$f(R,\mathcal {L}_{m})$$ that couples curvature, the matter Lagrangian density, a scalar field $$\Phi $$ , and its kinetic invariant $$X = g^{\mu \nu }\nabla _{\mu }\Phi \nabla _{\nu }\Phi $$ . Working with the explicit model $$f = R + \mathcal {L}_{m} + (\lambda /2)\,X$$ and a vanishing scalar potential, we compute the curvature invariants, the modified field equations, and the effective stress-energy components produced by the harmonic scalar profile $$\Phi (x,y) = a(x^{2}-y^{2})/2$$ in both backgrounds. The Ricci scalar vanishes for the Ori metric and obeys $$R = e^{f}(f_{,xx}+f_{,yy})$$ for the Ahmed metric; the kinetic invariant takes the explicit forms $$X = a^{2}(x^{2}+y^{2})$$ and $$X = a^{2}e^{f}(x^{2}+y^{2})$$ , respectively. Both metrics solve the field equations of the modified theory with anisotropic matter sources, and the chronology-violating regions $$g_{zz}<0$$ (Ori) and $$g_{\psi \psi }<0$$ (Ahmed) survive the modification. Energy-density profiles measured by a closed-timelike-curve observer match those measured by a static observer outside the chronology horizon, so the additional scalar degree of freedom in $$f(R,\mathcal {L}_{m},\Phi ,X)$$ gravity does not enforce a chronology-protection mechanism in either background. The conclusion mirrors the parallel result for the Li time-machine and supplies a consistency test for scalar-extended modified gravity in non-globally-hyperbolic settings.

India

Faizuddin Ahmed

Jordan

Ahmad Al-Badawi

Türkiye

İzzet Sakallı

Are Petrov type-N and D spacetimes admitting CTCs valid in $$f(R,\mathcal {L}_m,\Phi ,X)$$ gravity?

Previously, we proposed an infrared vacuum wave functional for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mi>N</mi><mo stretchy="false">)</mo></math> Yang-Mills theory peaked at thin center vortices and showed that it yields an area law for the Wilson loop. In this work, we use this wave functional to calculate the spatial ’t Hooft loop, for which we find a perimeter law, in accordance with ’t Hooft’s criterion for confinement.

Brazil

Germany

D.R. Junior

L.E. Oxman

H. Reinhardt

’t Hooft loop in a center-vortex wave functional

An attempt is made to present the effect of the exclusive decay of ZZ/WW gauge bosons at high energy colliders in the Randall–Sundrum (RS) model. In this paper, we investigate the $$l^{-}l^{+}\nu \overline{\nu }$$ final state at muon-TeV colliders through the exclusive decay of ZZ/WW gauge bosons in detail. The result shows that with fixed collision energies, cross-sections for $$l^{-}l^{+}\nu \overline{\nu }$$ production in final state depend strongly on the parameters of the unparticle physics, muon polarization coefficients, parameters on anomalous couplings and also KK-graviton propagators. With the benchmark background $$(\Lambda _{U}, d_{U}) = (1~\text {TeV}, 1.9),$$ the total cross-sections achieve the maximum value when both of muon beams polarize left or right. In case of the different polarization, the cross-section increases as the collision energy increases. The numerical evaluation shows that the cross-section for $$l^{-}l^{+}\nu \overline{\nu }$$ final state through the exclusive decay of WW charged bosons is much larger than that of ZZ neutral bosons under the same conditions. With the contribution of new physics in the RS model, the effect is greatly enhanced and the cross-sections for the production of $$l^{-}l^{+}\nu \overline{\nu }$$ final state can be measured in the future muon collisions.

Vietnam

Bui Giang

Dang Soa

Investigation of the $$l^{-}l^{+}\nu \overline{\nu }$$ final state at multi-TeV muon colliders through the exclusive decay of ZZ/WW gauge bosons in the Randall–Sundrum model

We study a $\textit{U}$ (1) extension of the Standard Model (SM) in which Dirac neutrino masses are generated radiatively at the one-loop level through the exchange of new beyond the SM fields. This framework establishes a direct connection between neutrino mass generation and the dark sector, with the stability of the dark matter ensured by a residual discrete $$ {\mathcal{Z}}_6 $$ symmetry arising from the spontaneous breaking of $\textit{U}$ (1) . We investigate the resulting charged lepton flavor violating processes and dark matter phenomenology, saturating relic observations and direct-detection constraints, and analyze the collider signatures of the dark sector at the Large Hadron Collider, its proposed high luminosity extension and at a future muon collider. We have identified excellent prospects for observing the considered dark matter candidates in these colliders, even with lower integrated luminosities than the proposed one.

China

Supriya Senapati

Chayan Majumdar

Utkarsh Patel

Sudhanwa Patra

Radiative Dirac neutrino masses and dark matter in a $\textit{U}$ (1) $\textit{B}$−$\textit{L}$ extended model

We study neutrino nonstandard interactions (NSI) induced by the trilinear <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>L</mi><mi>i</mi></msub><msub><mi>L</mi><mi>j</mi></msub><msubsup><mi>E</mi><mi>k</mi><mi>c</mi></msubsup></math> (LLE) couplings in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity-violating supersymmetry in a split-family spectrum where third-generation sleptons can be comparatively light. We systematically classify the relevant coupling patterns, derive the corresponding effective interactions and NSI parameters, and confront the resulting parameter space with a broad set of experimental constraints. We find that percent-level NSI can be realized in selected channels, with the largest magnitudes reaching <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϵ</mi><mrow><mi>e</mi><mi>e</mi></mrow></msub><mo>≃</mo><mn>8</mn><mo>%</mo></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϵ</mi><mrow><mi>μ</mi><mi>μ</mi></mrow></msub><mo>≃</mo><mn>3.8</mn><mo>%</mo></math>, while other entries are typically restricted to the subpercent level (including <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>ϵ</mi><mrow><mi>μ</mi><mi>τ</mi></mrow></msub><mo>≃</mo><mo>−</mo><mn>0.3</mn><mo>%</mo></math> in the viable off-diagonal case). We also highlight the structural origin of the different constraint patterns between <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mover accent="true"><mi>τ</mi><mo stretchy="false">˜</mo></mover><mi>R</mi></msub></math>- and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mover accent="true"><mi>τ</mi><mo stretchy="false">˜</mo></mover><mi>L</mi></msub></math>-mediated scenarios and comment on the relation to the Zee model.

United States

Fang Xu

Neutrino nonstandard interactions from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>L</mi><mi>L</mi><mi>E</mi></math>-type <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-parity violation

We present high-precision predictions for associated <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mi>W</mi></math> production at the LHC that incorporate the next-to-next-to-leading-order hard and soft functions as well as the complete next-to-next-to-next-to-leading-order scale-dependent terms derived from the corresponding anomalous dimensions. These higher-order corrections, which dominate the full perturbative results, increase the next-to-leading-order cross section by more than 10%. Based on the comparison with ATLAS and CMS measurements, we directly extract the Cabibbo-Kobayashi-Maskawa matrix element <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">|</mo><msub><mrow><mi>V</mi></mrow><mrow><mi>t</mi><mi>b</mi></mrow></msub><mo stretchy="false">|</mo><mo>=</mo><mn>0.99</mn><mo>±</mo><mn>0.03</mn><mo stretchy="false">(</mo><mrow><mi>expt</mi></mrow><mo stretchy="false">)</mo><mo>±</mo><mn>0.03</mn><mo stretchy="false">(</mo><mtext>theor</mtext><mo stretchy="false">)</mo></mrow></math> without assuming unitarity, achieving a precision comparable with the current world average value.

Jia-Le Ding

Hai Tao Li

Jian Wang

Approximate <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msup><mrow><mi mathvariant="normal">N</mi></mrow><mrow><mn>2</mn></mrow></msup><mi>LO</mi></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">N</mi><mn>3</mn></msup><mi>LO</mi></math> QCD predictions for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>t</mi><mi>W</mi></math> production

We propose a nonperturbative completion of two-point correlators in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mover accent="true"><mi>T</mi><mo stretchy="false">¯</mo></mover></math>-deformed conformal field theories (CFTs) and analyze their behavior at distance scales shorter than the fundamental length scale set by the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mover accent="true"><mi>T</mi><mo stretchy="false">¯</mo></mover></math> deformation. Building on the interpretation of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mover accent="true"><mi>T</mi><mo stretchy="false">¯</mo></mover></math> deformation as a coupling to two-dimensional quantum gravity with a unique built-in length scale, we advance the study of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mover accent="true"><mi>T</mi><mo stretchy="false">¯</mo></mover></math>-deformed CFTs as a toy model for Planckian physics. As we probe shorter distances, trans-Planckian oscillations are followed by a super-Planckian regime in which correlations are typically suppressed by geometric randomness, in contrast to the power-law growth characteristic of CFTs. Moreover, their dependence on distance becomes exponentially weaker, suggesting that the underlying geometric structure has been largely erased—a behavior broadly consistent with expectations for quantum spacetime in this regime.

Japan

Shinji Hirano

Vinayak Raj

Nonperturbative effects in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi><mover accent="true"><mi>T</mi><mo stretchy="false">¯</mo></mover></math>-deformed conformal field theories: A toy model for Planckian physics

We investigate thick-brane configurations in five-dimensional $$f(T,T_G)$$ modified teleparallel gravity. In five dimensions, the torsional Gauss–Bonnet invariant $$T_G$$ contributes dynamically, leading to genuinely new effects even at linear order. Within a warped geometry supported by a scalar field, we construct explicit solutions and show that the $$T_G$$ sector significantly modifies the brane structure. In particular, the coupling parameter controls the deformation of the warp factor and energy density; for sufficiently negative values it can induce a genuine two-peak internal structure. We further analyze the localization of spin-1/2 fermions via a Yukawa coupling. For odd Yukawa functions the system admits a normalizable chiral zero mode, while the opposite chirality remains delocalized. The massive Kaluza–Klein spectrum is strongly affected by the torsional Gauss–Bonnet term, which modifies the effective potentials and leads to the appearance of resonant quasi-localized states. Our results show that $$f(T,T_G)$$ gravity provides a richer framework for braneworld models, where torsional higher-order corrections play a key role in shaping both geometry and field localization.

A. Moreira

F. Belchior

Mexico

Shi-Hai Dong

Greece

Chile

E. Saridakis

Thick branes and fermion localization in five-dimensional $$f(T,T_G)$$ gravity

In this work, holographic approach has been used to analyse the transport properties of baryon rich back-reacted thermal plasma with finite ’t Hooft coupling correction. The dual bulk geometry is charged AdS black hole with higher derivative Gauss–Bonnet (GB) correction and string cloud. Specially, we have studied the nature of drag force, jet quenching parameter, screening length, radial profile and energy loss with respect to different parameters. The drag force and jet quenching parameter are enhanced with GB coupling, baryon and flavor density whereas the screening length reduces with these parameters. The radial profile and energy loss of the rotating quark has also been studied and it is observed that the radial profile decreases with increase in baryon potential and flavor density, temperature and angular frequency, whereas it is enhanced with conjugate momenta and GB coupling. Further, the energy loss of the quark grows with potential and flavor density, velocity and angular frequency and it is suppressed with GB coupling.

Rishi Pokhrel

Indra Chettri

Karma Sherpa

Tanay Dey

Transport properties of baryon rich back-reacted thermal plasma with finite ’t Hooft coupling correction