In this work, we studied the quasinormal modes (QNM) and shadow of a Schwarzschild Black hole (BH) with higher-order metric corrections, in the framework of Infinite Derivative theory of Gravity (IDG). We studied the effects on QNMs and shadow of the BH, which arises from the IDG’s corrections to the BH’s metric. We used 6th order Padé averaged WKB approximation method to study the QNMs of the BH perturbed by a scalar field. We analyze the dependence of the amplitude and damping of QNMs with respect to the free parameters. Next, we studied the time evolution of a scalar field around the BH spacetime. The QNMs have been calculated from the time profile of the evolution. Then we studied the shadow of the BH. The variation of the shadow radius due to inclusion of higher-order corrections was studied and the variation of the shadow radius with respect to the free parameters also studied. Furthermore, the dependence of the shadow radius on the mass of the BH is also studied. Finally, we constrained the free parameters associated with the correction terms using the data from the Keck and VLTI observation, and we obtained some bounds on the parameters.

India

Rupam Borah

Umananda Goswami

Quasinormal modes and shadows of black holes in infinite derivative theory of gravity

We study resonant production of pairs of Standard Model (SM-)like Higgs bosons, in the presence of new neutral Higgs states together with new colored scalars (stops or sbottoms) in loops within the Next-to-Minimal Supersymmetric Standard Model. This is used as a test case to prove that the Large Hadron Collider has sensitivity to a variety of effects stemming from interferences between resonant (heavy) Higgs diagrams and/or among these and nonresonant topologies involving loops of both tops and stops. These effects can alter significantly the naive description of individual <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>s</mi></mrow></math>-channel Breit-Wigner resonances, leading to distortions of the latter, which, on the one hand, may mask their presence but, on the other hand, could enable one to extract features of the underlying new physics scenario. This last aspect is made possible through a decomposition of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>g</mi><mi>g</mi><mo stretchy="false">→</mo><mi>h</mi><mi>h</mi></math> signal process into all its amplitude components, each of which has a well-defined coupling structure. Ultimately, such effects can be traced back to the relevant Feynman diagrams and can enable a detailed interpretation of this process. To illustrate this, we introduce various benchmark points that exhibit potentially observable features during the current and/or upcoming runs of the LHC in one or more of the three customary di-Higgs decay channels: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><msup><mi>τ</mi><mo>+</mo></msup><msup><mi>τ</mi><mo>−</mo></msup></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>γ</mi><mi>γ</mi></math>.

United Kingdom

Sweden

Stefano Moretti

Italy

Luca Panizzi

Jörgen Sjölin

Harri Waltari

Deconstructing resonant Higgs boson pair production at the LHC: Effects of colored and neutral scalars in the NMSSM test case

The three Standard Model neutrinos can have Majorana mass or strictly Dirac mass, but both scenarios are practically indistinguishable in neutrino oscillation experiments. If they are pseudo-Dirac, however, there will be new mass splittings among the pseudo-Dirac pairs, potentially leaving traces in neutrino oscillation phenomena. In this work, we use flavor ratios of astrophysical neutrinos to discriminate different possible mass spectra of pseudo-Dirac neutrinos. We show that it will be possible to impose robust bounds of order <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>δ</mi><msubsup><mrow><mi>m</mi></mrow><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></msubsup><mo>≲</mo><msup><mrow><mn>10</mn></mrow><mrow><mo>−</mo><mn>12</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mrow><mi>eV</mi></mrow><mrow><mn>2</mn></mrow></msup></mrow></math> on the new mass squared splitting involving the third pseudo-Dirac mass eigenstates (those with the least electron flavor composition) with the future experiment IceCube-Gen2. The derived sensitivity is robust because it only assumes an extragalactic origin for the astrophysical neutrinos and hierarchical pseudo-Dirac mass spectrum. In case the neutrino sources are known in the future, such bounds can potentially improve by up to five orders of magnitude, reaching <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>δ</mi><msubsup><mi>m</mi><mn>3</mn><mn>2</mn></msubsup><mo>≲</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>17</mn></mrow></msup><mtext> </mtext><mtext> </mtext><msup><mi>eV</mi><mn>2</mn></msup></math>.

Brazil

Chee Sheng Fong

Yago Porto

Constraining the pseudo-Dirac nature of neutrinos using astrophysical neutrino flavor data

We propose a quantum mechanical theory of quantum spaces described by large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> noncommutative geometry as a model for quantum gravity. The model admits a fuzzy sphere as a static solution. Over the fuzzy geometry, the quantum mechanics of the fermions is given by a sum of oscillators with equal frequency. The energy state where exactly half of the Fermi sea is filled contains the maximal amount of degeneracy. This state of the fuzzy sphere obeys the mass-radius relation of a Schwarzschild black hole if the fuzzy sphere is identified with the black hole horizon. Moreover, the set of states in the Fermi sea gives precisely the Bekenstein-Hawking entropy. We thus propose that quantum black holes are described by fuzzy spheres with a half-filled Fermi sea in our model. We also consider a system of two fuzzy spheres by embedding them as blocks in the matrix quantum mechanics. When the distance <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math> between the two fuzzy spheres is small, the total energy of the system can be computed using perturbation theory. We show that, in the leading order of large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> limit, the interaction energy depends on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>−</mo><mi>G</mi><msub><mi>M</mi><mn>1</mn></msub><msub><mi>M</mi><mn>2</mn></msub></math> exactly in the manner as in Newton gravity. To reproduce the correct <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math> dependence in the long range, we expect the inclusion of large <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> corrections and quantum effects will be needed.

Taiwan

Chong-Sun Chu

Matrix model proposal for quantum gravity and the quantum mechanics of black holes

Spain

Daniel Castillo

Canada

Lotta Jokiniemi

Pablo Soriano

Javier Menéndez

Corrigendum to “Neutrinoless ββ decay nuclear matrix elements complete up to N 2LO in heavy nuclei&#8221; [Physics Letters B 860 (2025) 139181]

We study the spectrum of scalar primary operators in any two-dimensional conformal field theory. We show that the scalars alone obey a nontrivial crossing equation. This extends previous work that derived a similar equation for Narain conformal field theories. Additionally, we show that at high temperature, the difference between the true scalar partition function and the one predicted from a semiclassical gravity calculation is controlled by: the modular integral of the partition function, the light states of the theory, and an infinite series terms directly related to the nontrivial zeros of the Riemann zeta function. We give several numerical examples and compute their modular integrals.

United States

Nathan Benjamin

Cyuan-Han Chang

A. Fitzpatrick

Tobi Ramella

Properties of scalar partition functions of 2d CFTs

We investigate the scattering amplitudes of massive Kaluza-Klein (KK) states in compactified five-dimensional warped gauge and gravity theories. Focusing on tree-level 2 → 2 processes, we analyze the leading-order amplitudes involving bulk KK matter fields and KK gauge/gravitational Goldstone bosons. By imposing the gauge theory equivalence theorem (GAET) and the gravitational equivalence theorem (GRET) within warped KK theories, we systematically reconstruct the leading-order amplitudes for physical KK gauge bosons and gravitons, thereby circumventing the intricate energy cancellations inherent in physical amplitudes. Within this framework, the correspondence between GAET and GRET arises as a direct manifestation of the leading-order double-copy relation in the high-energy expansion. This connection provides a foundation for extending the BCJ double-copy construction to four-point amplitudes involving bulk KK matter fields, and further generalizes to arbitrary $\textit{N}$-point cases, enabling a systematic derivation of the corresponding gravitational amplitudes with consistent incorporation of KK matter fields at leading order.

Kezhu Guo

Yanfeng Hang

Equivalence theorems and double-copy structure in scattering amplitudes of massive Kaluza-Klein states with matter interactions

Simultaneous measurement of mass and radius with high precision is essential to unravelling the equation of state of matter at the core of neutron stars. Measurement of massive pulsars indicates that they have to be stiff at low densities. In this work, an ensemble of agnostically constructed equations of state was studied for the mass-radius measurement. The radius of neutron stars obtained from the ensemble was confined within a 10.5–14.5 km bound. Among the NICER measurements, PSR J0437–4715 provides the most stringent constraint on the equation of state. It was found that the detection of stars with smaller radii would prefer a softer equation of state, and the detection of stars with larger radii would prefer a stiffer equation of state. However, irrespective of the detection of stars with a smaller or larger radius, the sound speed peak indicates that stars are likely to have a smooth phase transition at a few times saturation densities, and the matter at the core may not be pure conformal quark matter. A better precision of the radius measurement drastically increases the chances of constraining the equation of state. The equation of state would be more effectively constrained if the measurement of large-radius stars with high precision were to happen. Precise radius measurements of neutron stars with smaller radii provide limited constraints on the equation of state over the density range relevant to neutron stars, largely independent of the stellar mass. Also, measurements for different masses are necessary to constrain the equation of state at all density ranges relevant to neutron stars.

Asim Saha

Ritam Mallick

The prospect of confining the equation of state of neutron stars with future mass and radius measurements

It has been recently established in $\textit{Phys. Lett. B}$ (2025) 139260 that asymptotically flat black holes exist in pure gravity theories in dimension greater than four. We extend this result to asymptotically five dimensional Anti-de Sitter spacetimes and perform bottom-up holographic explorations: Hawking-Page phase transitions, quasinormal modes of black holes providing decay times of excitations in the finite temperature conformal field theory and U-shaped string probes leading to the quark-antiquark potential in the dual field theory. The gravitational action contains a bared, negative cosmological constant and an Einstein-Hilbert term, supplemented by an infinite series of higher-curvature terms of the family known as Quasi-topological (QT) Lagrangians, leading to a lapse function in terms of infinite series which can be resumed to an analytic function for different coupling choices. The QT terms are defined as those satisfying a Birkhoff’s theorem and possessing a holographic c-function, and exist at all orders in the curvature, for arbitrary dimension greater than four. Besides presenting the general formulae, we explore the physics of three specific cases leading to Hayward, Dymnikova and Bardeen-like regular black holes. We also found the field redefinition that permits recasting the $\textit{α}$ $\textit{W}$ correction of Type IIB supergravity on $$ {\mathcal{A}}_5 $$ × $\textit{S}$ as a series of QT terms. As anticipated in $\textit{JHEP}$ (2019) 062, due to the presence of a bared AdS radius $\textit{L}$, the perturbative field redefinition renormalizes Newton’s constant by an additive term of the form $\textit{α}$ $\textit{L}$ $\textit{R}$ and induces lower order terms of the form $$ {\alpha}^{\prime 3}{L}^{-4}{\mathcal{R}}^2 $$ and $$ {\alpha}^{\prime 3}{L}^{-2}{\mathcal{R}}^3 $$ , both of which can be simultaneously written as QT terms, without spoiling the structure of the highest curvature term of the form $$ {\alpha}^{\prime 3}{\mathcal{R}}^4 $$ . Before finishing, beyond holography, we also provide an extended thermodynamic setup, that via variations of the dimensionful $\textit{α}$ and $\textit{L}$, allow obtaining the Euler relation between finite thermodynamical quantities for the black hole of the theory.

Chile

Monserrat Aguayo

Leonardo Gajardo

Argentina

Nicolás Grandi

Javier Moreno

Julio Oliva

Mexico

Martín Reyes

Holographic explorations of regular black holes in pure gravity

The Cabibbo–Kobayashi–Maskawa matrix element $$|V_{\textrm{cb}}|$$ is an important Standard Model parameter, whose value can be determined by using the semi-leptonic decay $$B\rightarrow D^{*}\ell {\bar{\nu }}_\ell $$ . The perturbative QCD (pQCD) corrections to the $$B \rightarrow D^{*}$$ transform form factor $${{\mathcal {F}}}(w)$$ has been known up to the $$\hbox {N}^3$$ LO level, whose magnitude remains sensitive to the choice of renormalization scale $$\mu _r$$ . To improve the precision of $${{\mathcal {F}}}(w)$$ and hence $$|V_{\textrm{cb}}|$$ , we first apply the single-scale approach of Principle of Maximum Conformality (PMC) to eliminate the conventional (Conv.) renormalization scale dependence of the short-distance parameter $$\eta _A$$ and then predict the contribution of its unknown $$\hbox {N}^4$$ LO term via Bayesian analysis. In this paper, we adopt two probabilistic models for Bayesian analysis: the Cacciari–Houdeau model (CH model) and the geometric behavior model (GB model). It is shown that by using the PMC series in combination with Bayesian analysis, one can achieve high degree of reliability in estimating unknown higher-order terms. A more convergent behavior is achieved by applying the PMC, confirmed by the predicted $$\hbox {N}^4$$ LO contributions: for the CH model, $$\eta _A|_{\mathrm{Conv.}}^{\text {N}^{4}\text {LO}}=\{-\,0.0032,+\,0.0052\}$$ and $$\eta _A|_{\textrm{PMC}}^{\text {N}^{4}\text {LO}}=\{-\,0.0004,+\,0.0004\}$$ ; for the GB model, $$\eta _A|_{\mathrm{Conv.}}^{\text {N}^{4}\text {LO}}=\{-\,0.0049,+\,0.0075\}$$ and $$\eta _A|_{\textrm{PMC}}^{\text {N}^{4}\text {LO}}= \{-\,0.0007,+\,0.0007\}$$ . Comparing with the latest experimental measurements, we obtain $$|V_{\textrm{cb}}||_{\textrm{PMC}}=(40.58^{+0.53}_{-0.57})\times 10^{-3}$$ , which is consistent for both CH and GB models and in good agreement with the PDG world average, $$|V_{\textrm{cb}}|_{\textrm{PDG}}=(41.1\pm 1.2)\times 10^{-3}$$ within errors.

China

Wang Li

Xing-Gang Wu

Hua Zhou

Xu-Chang Zheng

Determination of $$|V_{\textrm{cb}}|$$ using Bayesian analysis of the $$B \rightarrow D^{*}\ell {\bar{\nu }}_\ell $$ semileptonic decay width with four-loop QCD corrections