An $\textit{SU}$(3) flavor projection operator technique is implemented to construct the baryon-meson scattering amplitude within the framework of the $1/N_c$ expansion of quantum chromodynamics (QCD), where $N_c$ represents the number of color charges. The operator technique is implemented to evaluate not only the lowest-order scattering amplitude but also effects from the first-order perturbative $\textit{SU}$(3) flavor symmetry breaking and strong isospin breaking. The most general expression is obtained by explicitly accounting for the effects of the decuplet-octet baryon mass difference. At order ${\cal{O}}(1/N_c^2)$ , a large number of unknown operator coefficients appear, and therefore, there is little additional predictive power unless leading and subleading terms are retained. Although the resultant expression is sufficiently general that it can be applied to any incoming and outgoing baryons and pseudo scalar mesons, provided that the Gell-Mann--Nishijima scheme is respected, results for $N\pi\to N\pi$ scattering processes are explicitly considered.

Víctor Miguel Banda Guzmán

Rubén Flores-Mendieta

Johann Hernández

Use of $\textit{SU}$(3) flavor projection operators to construct baryon-meson scattering amplitudes in the 1/ N$_{c}$ expansion * The authors are grateful to Consejo Nacional de Humanidades, Ciencias y Tecnologías (Mexico) for support through the $\textit{Ciencia de Frontera}$ project CF-2023-I-162

We constructed the ghost-free condition for nonlocal gravity using de-Sitter background field expansion and identified the structure of the nontrivial form factors. Our analysis shows that the particle spectrum of this model is nearly equivalent to general relativity (GR), with the potential addition of a scalar particle with positive mass $\textit{m}$. Additionally, by employing recursion relations, we established the equivalence between nonlocal gravity and higher-derivative gravity. Moreover, we provided a comprehensive proof of the stability of de-Sitter solution within the nonlocal framework.

China

Haiyuan Feng

Rong-Jia Yang

The stability of the de-Sitter universe in nonlocal gravity

The imaginary part of the effective action encodes vacuum instability and particle production in the background field. Two standard approaches are commonly used to derive it: the Bogoliubov method and the Green’s function method, which are usually expected to agree. However, in de Sitter spacetime they yield different results. We revisit this problem by introducing explicit time and momentum cutoffs in the Green’s function representation of the effective action. The apparent discrepancy is found to be due to the different limiting procedures in regularization, which reproduces the Bogoliubov result and the Green’s function result, respectively. Therefore, the two approaches are understood to be different regularization limits of the same expression, which clarifies the origin of their disagreement.

Yu Zhou

Hai-Qing Zhang

Imaginary part of the effective action in de Sitter spacetime with different regularization schemes

We investigate a new definition of holographic entanglement entropy in the framework of static patch holography for de Sitter space. Using the replica trick and twist operator formalism, we derive an entropy functional in dS expressed through de Sitter Green’s functions. Since the naive Ryu-Takayanagi prescription in de Sitter spacetime fails to satisfy strong subadditivity, we demand that our proposed formula be consistent with the fundamental entropic inequalities. The resulting conditions place nontrivial constraints on the undetermined parameter space of static patch holography. Our results demonstrate that entanglement inequalities provide a sharp diagnostic for candidate definitions of entanglement entropy in de Sitter holography and offer quantitative evidence in support of static patch holography as a consistent framework.

Shan-Ming Ruan

Japan

Yu-ki Suzuki

Toward a consistent definition of holographic entanglement entropy in de Sitter space

We uncover a surprising universal soft behavior (USB) of a de Sitter (dS) S-matrix for all exceptional effective field theories (EFTs) in dS space, stemming from the recently proposed generalized energy conservation condition. At leading order in the soft limit, the dS S matrices for all exceptional EFTs in four spacetime dimensions exhibit no scaling with the soft momentum, i.e., <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>lim</mi><mrow><mi>k</mi><mo stretchy="false">→</mo><mn>0</mn></mrow></msub><mi mathvariant="script">A</mi><mo stretchy="false">(</mo><mi>k</mi><mo stretchy="false">)</mo><mo>∼</mo><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math>, a feature we term USB. We specifically show that USB fixes the four-point amplitudes in Dirac-Born-Infeld theory and Special Galileon, and six-point amplitude in <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> nonlinear sigma model given the minimal derivative count. We then conjecture USB fixes the interactions of all exceptional EFTs to all orders, thereby providing a unification criterion for them. Our result further underpins the idea that <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Δ</mi><mo>≥</mo><mn>4</mn></math> exceptional theories in dS are characterized by the spectrum and stability requirement alone, resonating with the low energy theory of gravity-general relativity.

United Kingdom

Zong-Zhe Du

Soft unification of exceptional effective field theories in de Sitter space

We present a family of charged, traversable wormhole solutions in the presence of a cosmological constant. In de Sitter spacetime, two types of wormhole throats can exist–referred to as typical and cosmological throat–located at small and large radial values, respectively. In anti-de Sitter spacetime, the throat geometry allows for positive, zero, or negative curvature, enabling the possibility of an infinite throat area. We analyze the flare-out condition, a key requirement for the existence of traversable wormholes, which imposes constraints on the equation of state parameters governing the supporting matter. These solutions are shown to be of Petrov type <italic>D</italic>. Furthermore, we examine radial geodesics of null and timelike particles. In the de Sitter case, particles traverse the wormhole, passing from one throat to the other. In contrast, in the anti-de Sitter case, particles exhibit recurrent oscillatory motion between two asymptotic regions, cyclically disappearing and reappearing across the throats.

South Korea

Hyeong-Chan Kim

Wonwoo Lee

Charged wormholes in (anti-)de Sitter spacetime

We study cosmological correlators in de Sitter quantum gravity in the limit where $\textit{G}$ → 0. This limit is distinct from a nongravitational QFT because the gravitational constraints still force states and observables to be de Sitter invariant. We first examine a class of perturbative correlators that, in gauge-fixed form, are represented by the expectation value of a product of elementary fields on the late-time boundary. We formulate Feynman rules for our computations and enumerate some necessary, but not sufficient, conditions that must be imposed on states and operators to avoid group-volume divergences. These correlators are conformally invariant in all allowed perturbative states but never coincide with QFT vacuum-expectation values. For instance, our sample computations yield interesting non-Gaussianities even when the underlying vacuum wavefunction is Gaussian. However, we show that, in the presence of a heavy background state, it is possible to construct a separate class of state-dependent relational observables whose values approximate QFT correlators in the vacuum. This illustrates a key contrast in quantum gravity — between observables that are microscopically simple and observables whose expectation values in an appropriate background state lead to simple QFT-like correlators.

India

Tuneer Chakraborty

Ashik H

Suvrat Raju

Cosmological correlators in gravitationally-constrained de Sitter states

Based on $ (10087\pm 44)\times10^{6} $ $ J/\psi $ events collected with the BESIII detector, we search for the lepton number violating decay $ J/\psi \to K^+K^+e^-e^- + c.c. $ for the first time. The upper limit on the branching fraction of this decay is set to $ 2.1 \times 10^{-9} $ at the 90% confidence level with a frequentist method. This is the first search for $ J/\psi $ decays with a lepton number change by two, offering valuable insights into the underlying physical processes.

M. Ablikim

Russia

M.N. Achasov

Sweden

P. Adlarson

X.C. Ai

Germany

R. Aliberti

Italy

A. Amoroso

Q. An

Y. Bai

O. Bakina

Y. Ban

H.R. Bao

Poland

V. Batozskaya

Mongolia

K. Begzsuren

N. Berger

M. Berlowski

M.B. Bertani

D. Bettoni

F. Bianchi

E. Bianco

A. Bortone

I. Boyko

United States

R.A. Briere

A. Brueggemann

H. Cai

M.H. Cai

X. Cai

A. Calcaterra

G.F. Cao

N. Cao

Türkiye

S.A. Cetin

X.Y. Chai

J.F. Chang

T.T. Chang

G.R. Che

Y.Z. Che

C.H. Chen

Chao Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.L. Chen

S.M. Chen

T. Chen

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z. Chen

Z.K. Chen

J.C. Cheng

L.N. Cheng

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

J. Cottee-Meldrum

H.L. Dai

J.P. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denisenko

M. Destefanis

F. De Mori

B. Ding

X.X. Ding

Y. Ding

Y.X. Ding

J. Dong

L.Y. Dong

M.Y. Dong

X. Dong

M.C. Du

S.X. Du

X.L. Du

Y.Y. Duan

Z.H. Duan

P. Egorov

G.F. Fan

J.J. Fan

Y.H. Fan

J. Fang

S.S. Fang

W.X. Fang

Y.Q. Fang

R. Farinelli

L. Fava

F. Feldbauer

G. Felici

C.Q. Feng

J.H. Feng

Search for the lepton number violating process ${{\boldsymbol J}/{\boldsymbol\psi }{\bf\to}{\boldsymbol K}^{\bf +}{\boldsymbol K}^{\bf +}{\boldsymbol e}^{\bf -}{\boldsymbol e}^{\bf -}{\bf +}{\boldsymbol {c.c.}}}$ * This work is supported in part by National Key R&D Program of China under Contracts Nos. 2023YFA1606000, 2023YFA1606704; National Natural Science Foundation of China (NSFC) under Contracts Nos. 12035009, 11635010, 11935015, 11935016, 11935018, 12025502, 12035013, 12061131003, 12192260, 12192261, 12192262, 12192263, 12192264, 12192265, 12221005, 12225509, 12235017, 12361141819; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; CAS under Contract No. YSBR-101; 100 Talents Program of CAS; The Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; German Research Foundation DFG under Contract No. FOR5327; Istituto Nazionale di Fisica Nucleare, Italy; Knut and Alice Wallenberg Foundation under Contracts Nos. 2021.0174, 2021.0299; Ministry of Development of Turkey under Contract No. DPT2006K-120470; National Research Foundation of Korea under Contract No. NRF-2022R1A2C1092335; National Science and Technology fund of Mongolia; National Science Research and Innovation Fund (NSRF) via the Program Management Unit for Human Resources & Institutional Development, Research and Innovation of Thailand under Contract No. B50G670107; Polish National Science Centre under Contract No. 2024/53/B/ST2/00975; Swedish Research Council under Contract No. 2019.04595; U. S. Department of Energy under Contract No. DE-FG02-05ER41374

We investigate the soft behavior of the tree-level Rutherford scattering processes mediated via $\textit{t}$-channel one-graviton exchange. We consider two types of Rutherford scattering processes: a low-energy massless structureless projectile (up to spin-1) hits a static massive composite particle carrying various spins (up to spin-2), and slowly moving light projectile hits a heavy static composite target. The unpolarized cross sections in the first type exhibit universal forms at the first two orders in $ 1/M $ expansion, yet differ at the next-to-next-to-leading order, though some terms at this order still remain universal or depend on the target spin in a definite manner. The unpolarized cross sections in the second type are universal at the lowest order in projectile velocity expansion and through all orders in $ 1/M $ , independent on the spins of both projectile and target. The universality partially breaks down at relative order- $ v^2/M^2 $ , albeit some terms at this order still depend on the target spin in a specific manner.

Yu Jia

Jichen Pan

Jia-Yue Zhang

Soft pattern of gravitational Rutherford scattering from heavy target mass expansion * This work is supported in part by the National Natural Science Foundation of China (11925506, 12475090). J.-Y. Z. is supported in part by the US Department of Energy (DE-AC05-06OR23177), under which Jefferson Science Associates, LLC operates Jefferson Lab.

In gauge-gravity duality, the Hawking-Page (HP) process plays the important role of representing a confined-deconfined phase transition. For spaces that are asymptotically anti–de Sitter with a planar spatial boundary, there is no HP transition, unless some infrared energy scale is introduced. Massive gravity theories have been applied in the context of holography in order to represent systems with momentum dissipation. In this work, we study the HP transition for massive gravity in an asymptotically anti–de Sitter space with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="double-struck">R</mi><mi>n</mi></msup><mo>×</mo><mrow><msup><mrow><mi mathvariant="normal">S</mi></mrow><mrow><mn>1</mn></mrow></msup></mrow></math> boundary. It is shown that the graviton mass term produces an HP transition at a finite critical temperature.

Brazil

Nelson R.F. Braga

William S. Cunha

Hawking-Page transition in anti-de Sitter massive gravity with noncompact spatial boundary