This paper corroborates a statement that perturbative string theory does not admit a solution whose spacetime metric is de Sitter times a closed manifold, to all orders in the $\textit{α}$ and $\textit{g}$ expansions, under the assumption that the logarithm of the sphere partition function of Euclidean quantum gravity receives a nonzero contribution proportional to $$ \frac{1}{G_N} $$ in a saddle-point approximation. This assumption is related to the Gibbons-Hawking proposal that the entropy of the cosmological horizon of the static patch is $$ \frac{A}{4{G}_N} $$ . Evidence for the statement comes from independent approaches to the effective action of string theory, all of which agree that the tree-level action vanishes for closed Euclidean target-space solutions. One possible implication is that the state of the Universe will depart from an asymptotically de Sitter spacetime.

Israel

Yoav Zigdon

De Sitter in string theory vs. Gibbons & Hawking

We revisit the role of the trace sector of the graviton in covariant string amplitudes by constructing the ghost-number-three graviton vertex operator via BRST descent, imposing only the de Donder gauge condition without requiring tracelessness. The resulting operator is well defined even at zero momentum, while for nonzero momentum the trace-dependent sector of the descent chain forms a trivial BRST descent chain. Evaluating its disk one-point function in the presence of a D <italic>p</italic>-brane, we show that the trace-dependent term is essential for reproducing the correct graviton-brane coupling, canceling the Dirichlet-direction contributions and leaving the expected coupling to the world-volume components.

Japan

Isao Kishimoto

Tomohiko Takahashi

Mamiko Yamada

Graviton vertex operators in the de Donder gauge and BRST descent

In this paper, we investigate the almost $$\eta $$ -Ricci–Yamabe soliton as a fundamental geometric regulator for a static, spherically symmetric black hole coupled to an imperfect fluid. We have shown that the scaling parameter $$\omega (r)$$ is governed by thermodynamic friction along the radial vector field and the geometric coupling with the Hawking temperature: $$\alpha (r_H) S_{tt} = 2\pi T_H$$ , at the horizon. We also derive the Poisson equation along the gradient vector field of the soliton and prove that the flow’s kinematic expansion is explicitly dependent on the fluid’s equation of state $$\rho = \gamma \sigma $$ . Diverging from traditional methodologies that assume a geometric shape function a priori, we analytically proved the geometric flow endogenously transitions the black hole geometry into a traversable wormhole throat by regularizing the temporal coordinate and satisfying spatial flare-out condition. This transition occurs when fluid enters the dark energy era at $$\gamma = -1$$ and violates the Null Energy Condition $$\rho + \sigma < 0$$ , with the soliton strictly dominating the local curvature gradient $$\omega ^{\prime }(r_H) > f^{\prime \prime }(r_H)$$ to keep the throat open. Moreover, by smoothly attenuating at spatial infinity, the soliton preserves the exact cosmological spacetime. Finally, through tensorial perturbation analysis, we demonstrate that the geometric flow introduces a localized dissipative mechanism that the perturbation evolution reduces to a damped wave equation, imposing geometric drag on the manifold.

India

Jay Singh

 Jaswant

Traversable wormhole de-singularization: almost $$\eta $$ -Ricci–Yamabe solitons in static spherically symmetric imperfect fluid spacetimes

Soft de Sitter Effective Theory is a well-motivated candidate for the correct effective late-time description of equal-time correlation functions in de Sitter space. In this work, we study its application to theories that enjoy classical conformal invariance, using the conformally-coupled $\textit{ϕ}$ -theory as a toy model. While quantum effects generate non-trivial late-time dynamics in such models, we argue that it is not described by the standard construction of the effective theory as discussed thus far in the literature. We show that the tree-level matching of the trispectrum onto the effective theory does not fit into the expected power-counting scheme, and we contrast it with the matching of the tree-level bispectrum in the conformally-coupled $\textit{ϕ}$ -theory, where it works consistently. We then propose a prescription to identify the leading superhorizon degrees of freedom in such theories, which should serve as the starting point for the construction of their late-time effective description. The interpretation of logarithms of the form ln(−$\textit{kη}$) in this context is briefly discussed.

Spain

Maria Fiore

Andrea Sanfilippo

Classical conformal invariance and superhorizon dynamics in de Sitter

Based on $ (10087\pm44)\times10^{6} $ $ J/\psi $ events collected with the BESIII detector, the $ J/\psi\rightarrow \gamma K^{0}_{S}K^{0}_{S}\pi^{0} $ and $ J/\psi\rightarrow \gamma \pi^{0}\pi^{0}\eta $ processes are studied. The $ X(2370) $ is observed in both the $ K^{0}_{S}K^{0}_{S}\pi^{0} $ and $ \pi^{0}\pi^{0}\eta $ invariant mass spectra, with statistical significances greater than $ 14\sigma $ and $ 20\sigma $ , respectively. By combining measurements from these processes with those from the previously reported $ J/\psi\rightarrow \gamma K^{0}_{S}K^{0}_{S}\eta^{\prime} $ process, the mass and width of the $ X(2370) $ are determined to be $ 2359^{+13}_{-14}\; \text{MeV}/c^{2} $ and $ 170^{+44}_{-29}\; \text{MeV} $ , respectively. In addition, the decay $ X(2370)\to a_{0}(980)^{0}\pi^{0} $ with $ a_{0}(980)^{0}\to \pi^{0}\eta $ is observed with a statistical significance exceeding $ 9\sigma $ . The properties of the $ X(2370) $ —decay pattern similarities to that of $ \eta_{c} $ , are consistent with those of a pseudoscalar glueball.

China

M. Ablikim

Russia

M.N. Achasov

Sweden

P. Adlarson

X.C. Ai

Italy

C.S. Akondi

Germany

R. Aliberti

A. Amoroso

Q. An

Y.H. An

M.S. Anderson

Y. Bai

O. Bakina

H.R. Bao

X.L. Bao

M. Barbagiovanni

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. Briere

A. Brueggemann

D. Cabiati

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

C. Chen

G. Chen

H.S. Chen

H.Y. Chen

M.L. Chen

S.J. Chen

S.M. Chen

T. Chen

W. Chen

X.R. Chen

X.T. Chen

X.Y. Chen

Y.B. Chen

Y.Q. Chen

Z.K. Chen

J. Cheng

L.N. Cheng

S.K. Choi

X. Chu

G. Cibinetto

F. Cossio

United Kingdom

J. Cottee-Meldrum

H.L. Dai

J.P. Dai

X.C. Dai

A. Dbeyssi

R.E. de Boer

D. Dedovich

C.Q. Deng

Z.Y. Deng

A. Denig

I. Denisenko

M. Destefanis

F. De Mori

E. Di Fiore

X.X. Ding

Y. Ding

Y.X. Ding

J. Dong

L.Y. Dong

M.Y. Dong

X. Dong

Z.J. Dong

M.C. Du

S.X. Du

X.L. Du

Y.Q. 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

Observation of the ${\boldsymbol X(2370)}$ in ${{\boldsymbol J}/\boldsymbol\psi\rightarrow\gamma K^{0}_{S}K^{0}_{S}\pi^{0}}$ and ${J/\psi\rightarrow\gamma \pi^{0}\pi^{0}\eta}$ * This work is supported in part by the National Key R&D Program of China under Contracts Nos. 2025YFA1613900, 2023YFA1606000, 2023YFA1606704; National Natural Science Foundation of China (NSFC) under Contracts Nos. 11635010, 11935015, 11935016, 11935018, 12025502, 12035009, 12035013, 12061131003, 12192260, 12192261, 12192262, 12192263, 12192264, 12192265, 12221005, 12225509, 12235017, 12342502, 12361141819, 12535005; the Chinese Academy of Sciences (CAS) Large-Scale Scientific Facility Program; the Strategic Priority Research Program of Chinese Academy of Sciences under Contract No. XDA0480600; CAS under Contract No. YSBR-101; 100 Talents Program of CAS; China Postdoctoral Science Foundation under Contracts Nos. GZC20252256, 2025M773423; The Institute of Nuclear and Particle Physics (INPAC) and Shanghai Key Laboratory for Particle Physics and Cosmology; Agencia Nacional de Investigación y Desarrollo de Chile (ANID), Chile under Contract No. ANID CCTVal CIA250027; ERC under Contract No. 758462; 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, 2023.0315; 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; Polish National Science Centre under Contract No. 2024/53/B/ST2/00975; STFC (United Kingdom); Swedish Research Council under Contract No. 2019.04595; U. S. Department of Energy under Contract No. DE-FG02-05ER41374

Parallel to the AdS Scale-Space construction in [1], we construct a ($\textit{d}$ + 1)-dimensional de Sitter QFT directly from $\textit{d}$-dimensional CFT data. The dS geometry is the moduli space of oriented balls, and the lifted operators are obtained by conformal-family Casimir completion. The Euclidean parent CFT gives a finite wavefunction representation, while the Minkowski parent CFT gives a double-time representation that is unitary in the parent-time polarization. This provides a CFT-based framework for reexamining puzzles of dS and double-time QFT.

Haitang Yang

Exact and finite de Sitter QFT from CFT

We study three-gluon scattering amplitudes in global de Sitter spacetime, in the angular momentum basis of $\textit{SO}$(1$\textit{,}$ 4) symmetry representations. At the tree level, they are determined by the intertwiner integrals of harmonic one-forms on the three-sphere. We derive a general formula valid for all helicity configurations of incoming and outgoing gluons and express the amplitudes in terms of Wigner 3j symbols.

Tomasz Taylor

Bin Zhu

Three-gluon scattering amplitude in de Sitter spacetime

The one-state statement for closed universes has sparked considerable discussion. In this paper, we examine its physical meaning in the context of the Hartle-Hawking state and de Sitter space. We argue that the one-state property of closed universes is fully compatible with the finite-dimensional quantum mechanics experienced by observers inside de Sitter space, and that this compatibility requires neither mixing of $\textit{α}$-sectors nor any modification of the rules of the gravitational path integral. The apparent tension is resolved by sharply distinguishing the baby-universe Hilbert space (the space of closed universes viewed from the $\textit{outside}$) from the bulk Hilbert space that governs quantum mechanics for an observer $\textit{inside}$ a single de Sitter universe.

Ying Zhao

“It from Bit”: the Hartle-Hawking state and quantum mechanics for de Sitter observers

We demonstrate that all anti-self-dual Einstein metrics with non-zero cosmological constant Λ locally arise from solutions of a single second order PDE introduced by Lipstein and Nagy. We show how this equation fits into the heavenly formalism of Plebański, and establish a Lax pair. Finally we show how Plebański’s second heavenly equation arises in the limit as Λ → 0.

Maciej Dunajski

Timothy Moy

Heavenly equations in de Sitter space

We compute the holographic complexity of conformal quantum fields in rigid global de Sitter spacetime (dS ) using the volume and action prescriptions. First we consider AdS spacetime in global dS foliations, and compute the complexity of the CFT supported on the global dS conformal boundary. Next, we consider CFT supported on a global dS (UV) brane embedded in AdS spacetime, and compute the holographic complexity in this brane set up. We compare and contrast the results in the two cases, as well as with related results in the literature obtained in alternative holographic set ups involving patches of de Sitter spacetime covered by static coordinates or conformal (Poincaré) coordinates.

Sanhita Parihar

Shubho Roy

Holographic complexity of conformal fields in global de Sitter spacetime