We discuss aspects of the quantum Lyapunov exponent $\textit{λ}$ in theories with an exactly marginal SYK-like random interaction, where $\textit{λ}$ can be computed as a continuous function of the interaction strength $$ \mathcal{J} $$ . In 1$\textit{d}$, we prove a conjecture from [1] which states that at small $$ \mathcal{J} $$ , $\textit{λ}$ can be found by considering a specific limit of the four-point function in the decoupled theory. We then provide additional evidence for the 2$\textit{d}$ version of this conjecture by discussing new examples of Lyapunov exponents which can be computed at weak coupling.

Israel

Rohit Kalloor

United States

Adar Sharon

More on chaos at weak coupling

The sensitivity of axion dark matter searches depends on the signal window that results from the velocity dispersion of axion dark matter. Since the ratio of signal windows is about 6500 between the standard halo and the big flow axion dark matter, each axion dark matter search usually uses a separate data acquisition (DAQ) channel with a different frequency resolution bandwidth (RBW). In this work, we demonstrate axion dark matter searches covering the standard halo, the tidal stream, and the big flow employing a DAQ channel starting with a single high resolution RBW, without sacrificing the DAQ efficiency, where the DAQ process includes online fast Fourier transforms and writing the outputs to disk. Assuming the total amount of data is sensitive to Dine-Fischler-Srednicki-Zhitnitskii (DFSZ) axion dark matter that follows the standard halo model and makes up 100% of the local dark matter density, the same data can also be used for the tidal stream and the big flow axion dark matter searches that would be sensitive to DFSZ axion dark matter that constitute 19.2% and 12.4% of the local dark matter densities, respectively, at a 90% confidence level. We also report that the filtering of the individual power spectra acquired with a relatively high resolution RBW e.g., for the big flow search can prevent a possible significant degradation in the signal to noise ratio from the searches in the lower resolution RBW’s, i.e., the standard halo and tidal stream searches.

Andrew Yi

South Korea

Byeong Ko

Axion dark matter searches from the standard halo over the tidal stream to the big flow

We study celestial amplitudes for the S-matrix of the 2d integrable Bullough-Dodd model. This model has bound states that appear as poles in the physics strip of its 2d S-matrix, which complicates the computation of celestial amplitudes. However, it turns out that the celestial amplitudes are, in fact, well-structured. The celestial bootstrap (arising from the unitarity and crossing symmetry of 2d S-matrix) can be decomposed into a finite-dimensional linear space, whose base-integrals evaluate into harmonic numbers. This clean structure replaces the complicated integration with simple algebra of elementary functions, and the celestial bootstrap reduces to a programmable recursion process of simple algebra. Interestingly, this linear space has a subspace that happens to cover the celestial bootstrap of the Sinh-Gordon model studied by . So the celestial dual of these 2d integrable models turns out to be ‘bootstrapable’ in the practical sense, that is, a programmable recursion process.

China

Minjia Wang

Wei Fan

The integrable Bullough-Dodd model under celestial holography

We use holography to study correlation functions of local operators in maximally supersymmetric Yang-Mills theories arising on the world-volume of D$\textit{p}$-branes in the large-$\textit{N}$ and strong-coupling limit. The relevant supergravity backgrounds obtained from the near-horizon limit of the D$\textit{p}$-branes enjoy a scaling similarity, which leads to an auxiliary AdS space of fractional dimension. This suggests that holographic correlation functions in this setup can be computed by integrating standard CFT correlators over the auxiliary extra dimensions. We apply this prescription to analytically compute two- and three-point correlators of scalar operators. The resulting two-point functions take a familiar CFT form but with shifted conformal dimensions, while the three-point correlators have a much more involved position dependence which we calculate explicitly in terms of a sum of Appell functions.

Belgium

Nikolay Bobev

Guillermo Mera Álvarez

Hynek Paul

Correlation functions for non-conformal D$\textit{p}$-brane holography

We describe the most general local, Lorentz-invariant, effective field theory of scalars, fermions and gauge bosons up to mass dimension 6. We first obtain both a Green and a physical basis for such an effective theory, together with the on-shell reduction of the former to the latter. We then proceed to compute the renormalization group equations for the bosonic operators of this general effective theory at one-loop order.

Spain

Renato Fonseca

Italy

Pablo Olgoso

José Santiago

Renormalization of general Effective Field Theories: formalism and renormalization of bosonic operators

The observation of a resonance structure in the opening angle of the electron-positron pairs in the $$^{7}$$ Li(p,e $$^+$$ e $$^-$$ ) $$^{8}$$ Be reaction was claimed and interpreted as the production and subsequent decay of a hypothetical particle (X17). Similar excesses, consistent with this particle, were later observed in processes involving $$^{4}$$ He and $$^{12}$$ C nuclei with the same experimental technique. The MEG II apparatus at PSI, designed to search for the $$\mu ^+ \rightarrow \textrm{e}^+ \gamma $$ decay, can be exploited to investigate the existence of this particle and study its nature. Protons from a Cockroft–Walton accelerator, with an energy up to 1.1 MeV, were delivered on a dedicated Li-based target. The $$\gamma $$ and the e $$^{+}$$ e $$^{-}$$ pair emerging from the $$^8\textrm{Be}^*$$ transitions were studied with calorimeters and a spectrometer, featuring a broader angular acceptance than previous experiments. We present in this paper the analysis of a four-week data-taking in 2023 with a beam energy of 1080 keV, resulting in the excitation of two different resonances with Q-value 17.6 and 18.1 MeV. No significant signal was found, and limits at 90% C.L. on the branching ratios (relative to the $$\gamma $$ emission) of the two resonances to X17 were set, $$R_{17.6} <{1.8}\,\times \,10^{-6}$$ and $$R_{18.1} < {1.2}\,\times \,10^{-5}$$ in the mass range between $${16.5}\hbox { MeV}/\hbox {c}^{2}$$ and $${17.1}\hbox { MeV}/\hbox {c}^{2}$$ .

Russia

K. Afanaciev

A. Baldini

Japan

S. Ban

H. Benmansour

G. Boca

P. Cattaneo

G. Cavoto

F. Cei

M. Chiappini

A. Corvaglia

Switzerland

G. Maso

A. Bari

M. Gerone

L. Barusso

M. Francesconi

L. Galli

G. Gallucci

F. Gatti

L. Gerritzen

F. Grancagnolo

E. Grandoni

M. Grassi

D. Grigoriev

M. Hildebrandt

United Kingdom

F. Ignatov

F. Ikeda

T. Iwamoto

S. Karpov

P. Kettle

N. Khomutov

A. Kolesnikov

N. Kravchuk

V. Krylov

N. Kuchinskiy

F. Leonetti

W. Li

V. Malyshev

A. Matsushita

M. Meucci

S. Mihara

W. Molzon

T. Mori

D. Nicolò

H. Nishiguchi

A. Ochi

W. Ootani

A. Oya

D. Palo

M. Panareo

A. Papa

V. Pettinacci

A. Popov

F. Renga

S. Ritt

M. Rossella

A. Rozhdestvensky

S. Scarpellini

P. Schwendimann

G. Signorelli

M. Takahashi

Y. Uchiyama

A. Venturini

B. Vitali

C. Voena

K. Yamamoto

R. Yokota

T. Yonemoto

Search for the X17 particle in $$^{7}\textrm{Li}(\textrm{p},\textrm{e}^+ \textrm{e}^{-}) ^{8}\textrm{Be}$$ processes with the MEG II detector

I investigate the higher dimensional black holes of quartic quasitopological-scalar gravity within the scope of extended quasitopological electromagnetism. It is demonstrated that only positive values of the quartic quasitopological parameter can result in physically acceptable solutions. In accordance with the values of the mass, conformal coupling constants, and quasitopological electromagnetic charges, the derived solution characterizes the dyonic hairy black holes with a single horizon, two horizons, and naked singularity. I also demonstrate that this solution has an essential curvature singularity at the centre $$r=0.$$ Additionally, the thermodynamic and conserved quantities for the resultant solution are worked out and the extended first law satisfied by these quantities is established. Ultimately, I address the consequences of a scalar field and electromagnetic charges on the local thermodynamic stability of dyonic hairy black holes.

Pakistan

Askar Ali

Black holes of quartic quasitopological gravity, conformal scalar field and extended quasitopological electromagnetism

We study the sphere partition function of 3d $$ \mathcal{N} $$ = 2 holographic SCFTs arising on the worldvolume of $\textit{N}$ coincident M2-branes in the presence of squashing and real mass deformations. We argue that the all-order large $\textit{N}$ perturbative expansion of the partition function resums into a compact expression in terms of an Airy function. We provide ample evidence for this conjecture using numerical methods, saddle point analysis in the ’t Hooft limit, and the relation of the squashed sphere partition function to the Cardy-like limit of the superconformal index. We also discuss the relation of our results to topological string theory and the statistical mechanics of Fermi gases. Our conjecture has a bearing on the AdS/CFT correspondence and the structure of perturbative M-theory corrections to 11d supergravity which we discuss.

Pieter-Jan Smet

Junho Hong

France

Valentin Reys

Xuao Zhang

An Airy tale at large $\textit{N}$

Axions arising as modes of higher-dimensional gauge fields are known to offer a compelling solution to the axion quality problem and to naturally arise in string theory. In this context, it is interesting to ask how we would interpret an experimental measurement of the axion decay constant $\textit{f}$. I give several arguments for, as well as concrete examples in string theory of, the existence in such a model of an axion string with tension of order 2$\textit{πS}$ $\textit{f}$ , where $\textit{S}$ is the instanton action. Furthermore, in models of this type axion strings are typically fundamental objects (rather than solitons), whose tension is at or above the fundamental cutoff of the theory. As a result, I argue that for an extra-dimensional QCD axion, it is likely that the fundamental cutoff scale lies at most two orders of magnitude above $\textit{f}$. In addition to these core arguments, this paper begins with a self-contained introduction to the physics of extra-dimensional axions and ends with some comments on axion physics in relation to chiral fermions.

Matthew Reece

Extra-dimensional axion expectations

In this study, we proceed to investigate the Thurston geometries from the point of view of their Poisson-Lie (PL) T-dualizability. First of all, we find all subalgebras of Killing vectors that generate group of isometries acting freely and transitively on the three-dimensional target manifolds, where the Thurston metrics are defined. It is shown that three-dimensional Lie subalgebras are isomorphic to the Bianchi type algebras. We take the isometry subgroup of the metric as the first subgroup of Drinfeld double. In order to investigate the non-Abelian T-duality, the second subgroup must be chosen to be Abelian. Accordingly, the non-Abelian target space duals of these geometries are found via PL T-duality approach in the absence of <italic>B</italic>-field. We also comment on the conformal invariance conditions of the T-dual <italic>&#963;</italic>-models under consideration.