It is notoriously difficult to construct a stable non-singular bouncing cosmology that avoids all possible instabilities throughout the entire evolution of the universe. In this work, we explore whether a non-singular bounce driven by a specific class of modifications of General Relativity, the vector-tensor generalized Proca theories, can be constructed without encountering any pathologies in linear perturbation theory. We find that such models unavoidably lead either to strong coupling in the tensor or the scalar sector, or instabilities in the matter sector during the bouncing phase. As our analysis is performed in a gauge-independent way, this result can be cast in the form of a no-go theorem for non-singular bounces with generalized Proca. In contrast to the no-go theorem found for Horndeski theories, however, it cannot be evaded by considering beyond generalized Proca theory. At the core of our result lies the non-dynamical nature of the temporal component of the vector field, which renders it an ill-suited mediator for a bouncing solution.

Switzerland

Lara Bohnenblust

Germany

Serena Giardino

Lavinia Heisenberg

Nadine Nussbaumer

To bounce or not to bounce in generalized Proca theory and beyond

We study the analytic continuation in the spin of the planar spectrum of ABJM theory using the integrability-based Quantum Spectral Curve (QSC) method. Under some minimal assumptions, we classify the analytic properties of the Q-functions appearing in the QSC compatible with the spin being non-integer. In this way, we find not one but $\textit{two}$ distinct possibilities. While one is related to standard Regge trajectories, we show that the second choice can be used to build bridges which connect leading and subleading Regge trajectories, thus giving a shortcut to reach infinitely many sheets of the spin Riemann surface without going explicitly around the branch points in the complex spin plane. Moreover, the bridges are exact spin reflections of standard Regge trajectories. Together, these results reveal the existence of a hidden symmetry which we call “twist/co-twist symmetry”: every non-BPS local operator has an exact image — living below unitarity on a different Regge trajectory — with the same ∆ and the spin flipped by a Weyl reflection. We discuss how an analogous phenomenon, based on the same mechanism at the level of the QSC, also occurs at non-perturbative level in $$ \mathcal{N} $$ =4 SYM. This provides a framework to understand recent independent observations of the symmetry in this model at weak and strong coupling. We present numerical results for Regge trajectories in planar ABJM theory, in particular we compute exactly the coupling dependence of the position of the leading Regge pole in the correlator of four stress tensors. The shape of this leading trajectory shows a behaviour at weak coupling that strongly resembles the BFKL limit in $$ \mathcal{N} $$ =4 SYM.

Italy

Nicolò Brizio

Andrea Cavaglià

Roberto Tateo

Valerio Tripodi

Regge trajectories and bridges between them in integrable AdS/CFT

It is long known that quantum Calogero models feature intertwining operators, which increase or decrease the coupling constant by an integer amount, for any fixed number of particles. We name these as “horizontal” and construct “vertical” intertwiners, which $\textit{change the number of interacting particles}$ for a fixed but integer value of the coupling constant. The emerging structure of a grid of intertwiners exists only in the algebraically integrable situation (integer coupling) and allows one to obtain each Liouville charge from the free power sum in the particle momenta by iterated intertwining either horizontally or vertically. We present recursion formulæ for the intertwiners as a factorization problem for partial differential operators and prove their existence for small values of particle number and coupling. As a byproduct, a new basis of non-symmetric Liouville integrals appears, algebraically related to the standard symmetric one.

Chile

Francisco Correa

Luis Inzunza

Olaf Lechtenfeld

Coupling and particle number intertwiners in the Calogero model

We show that the near-brane back-reaction of M2 branes ending on M5 branes has a rich “spike structure” that is determined by partitioning the numbers of M2 branes that are terminating on groups of M5 branes. The near-brane limit of the metric describing these branes has an AdS factor, implying the existence of a dual CFT. Each partition of the M2 and M5 charges among spikes gives rise to a different “mohawk” revealing a new layer of brane fractionation. We conjecture that all these mohawks are dual to ground states of near-brane-intersection CFT’s. We show that the supergravity solutions describing these mohawks are part of the large families of AdS × $\textit{S}$ × $\textit{S}$ solutions described in [1]. We identify precisely which of these families are relevant to brane intersections and show that the AdS invariance emerges from the self-similarity of the spikes.

France

Iosif Bena

Soumangsu Chakraborty

Dimitrios Toulikas

United States

Nicholas Warner

The M2-M5 Mohawk

In 1+1 dimensional conformal field theory with a boundary the boundary contribution to the entanglement entropy is determined by a single number $\textit{g}$ effectively counting the boundary degrees of freedom. In contrast, in 1+1 dimensional interface CFTs the corresponding quantity is a non-trivial $\textit{function}$ depending on the position of the interval relative to the interface, giving access to much more detailed information about the defect. In this work we determined this $\textit{g}$-function in several examples using holography and derive some of its basic properties from holography and strong subadditivity.

Spain

Evangelos Afxonidis

Andreas Karch

Chitraang Murdia

The boundary entropy function for interface conformal field theories

We investigate how competitive gravitational wave detectors can be to current and near-future colliders in probing a model where the new physics is completely encapsulated in a modified scalar sector. For this, we study a model where an additional logarithmic term arises in the scalar potential due to a non-trivial path integral measure, which is constructed using effective field theory. This new term alters the dynamics of cosmological phase transitions and could lead to potentially detectable gravitational waves from the early Universe. Our results confirm the expectation that the intensity of such spectrum is highly correlated to the scalar field’s self-coupling, and that gravitational wave experiments could therefore be used to probe these couplings with an accuracy competitive with the projected sensitivity of near-future colliders.

Brazil

Bruno Berganholi

Gláuber Dorsch

Iberê Kuntz

Beatriz Sena

Giovanna Valle

Cosmological phase transitions from the functional measure

We study $$ \frac{1}{4} $$ -BPS Wilson loops in four-dimensional SU($\textit{N}$) $$ \mathcal{N} $$ = 2 super-Yang-Mills theories with conformal matter in an arbitrary representation $$ \mathcal{R} $$ . These operators are formed of two meridians on the two-sphere separated by an arbitrary opening angle. We conjecture that these observables are encoded in a modification of Pestun’s matrix model. The matrix representation of these operators resembles that of the $$ \frac{1}{2} $$ -BPS circular Wilson loop, differing only for a rescaling in the exponent. We compare the matrix model predictions with an explicit three-loop calculation in flat space based on standard Feynman-diagram techniques, finding perfect agreement. Finally, exploiting the matrix model representation of these Wilson loops, we study the large-$\textit{N}$ limit at strong coupling of $$ \mathcal{N} $$ = 2 superconformal QCD, finding a surprising transition in the vacuum expectation value for a critical opening angle.

L. Griguolo

Poland

L. Guerrini

A. Testa

Into the wedge of $$ \mathcal{N} $$ = 2 superconformal gauge theories

The $$ \frac{1}{2} $$ -BPS indices of $$ \mathcal{N} $$ = 4 Super Yang-Mills theory with unitary, orthogonal, and symplectic groups all admit $\textit{q}$-expansions suggesting an interpretation in terms of D- branes in the dual bulk AdS string theories. We present a derivation of these expansions in the corresponding bulk duals by quantizing the moduli space of $$ \frac{1}{2} $$ -BPS giant gravitons using supersymmetric localization, extending and clarifying our study in arxiv:2312.14921. We perform a detailed analysis of the one-loop fluctuations around the maximal giants (the fixed points), and show how the Hamiltonian analysis is recovered from the functional integral for the equivariant index. We show that the analytic continuation for these giant graviton expansions observed in the literature maps precisely to a wall-crossing phenomenon for the index. In the case of orthogonal and symplectic gauge groups, the $\textit{ℤ}$ quotient in the bulk leads to a corresponding projection in the $\textit{q}$-expansion. Additional terms in the expansion related to the Pfaffian operator arise from topologically stable branes in the bulk dual on AdS × $$ {\mathbbm{RP}}^5 $$ .

United Kingdom

Giorgos Eleftheriou

Sameer Murthy

Taiwan

Martí Rosselló

Localization and wall-crossing of giant graviton expansions in AdS

In this paper, we conduct a data-driven study of the production of softened hadrons and their contribution to the transverse momentum spectrum. To this end, we assume that the production of charged particles at soft and hard scales fundamentally results from the fragmentation of color strings. We analyze the $$\textit{p}_\text {T}$$ -spectrum data from pp to AA collisions at LHC energies reported by the ALICE Collaboration, finding that, in all cases, the data can be collapsed into a $$\textit{p}_\text {T}$$ -exponential trend in the range 1 GeV $$<\textit{p}_\text {T}<$$ 6 GeV. With this insight, the description of the $$\textit{p}_\text {T}$$ -spectrum should contain information on the charged particle production coming from two different sources: fragmentation of color strings and collective phenomena that redistribute the transverse momentum and enhance the production of particles at intermediate $$\textit{p}_\text {T}$$ . We also found different relations between the effective temperature, multiplicity, and average $$\textit{p}_\text {T}$$ for pp and AA collisions, indicating inherent dissimilarities between small and large colliding systems. In contrast, the contribution of the softened hadrons to the $$\textit{p}_\text {T}$$ -spectrum and average $$\textit{p}_\text {T}$$ collapse onto scaling laws. Our results show that the physical mechanisms producing softened hadrons have similar origins for all colliding systems, revealing a stronger dependence on freeze-out parameters rather than the system size.

Mexico

D. Herrera

J. García

A. Téllez

E. Cuautle

J. Ramírez

Scaling laws for softened hadron production at LHC energies

Nonlinear electrodynamics has been an important area of research for a long time. Investigations based on nonlinear Lagrangians, such as Euler–Heisenberg and Born–Infeld, are instrumental in exploring the limits of classical and quantum field theories, providing valuable insights into strong-field phenomena. In this context, this work considers how light propagates in strong-field environments, where such nonlinearities play significant roles, offering a way to investigate events in high-energy astrophysics, quantum optics, and fundamental physics beyond classical Maxwell’s framework. Here, several aspects of light propagation in nonlinear electrodynamics are discussed. Phase and group velocities are derived and several interesting behaviors are unveiled, such as birefringence, non-reciprocal propagation, and asymmetries between phase and group velocities in special configurations. Specific solutions based on commonly studied nonlinear theories are also investigated, and phenomena like slow-light and one-way propagation are discussed.

T. Cruz

V. De Lorenci

E. Guzmán-Herrera

C. Ribeiro

Exploring light propagation in nonlinear electrodynamics: phase and group velocities and related phenomena