In this work, we develop machine learning techniques to study nonperturbative scattering amplitudes. We focus on the two-to-two scattering amplitude of identical scalar particles and study a toy model where we set the double discontinuity to zero, thereby simplifying the problem numerically. Neural networks provide an efficient parameterization for scattering amplitudes, offering a flexible toolkit to describe the details of their nonperturbative structure. Combined with the bootstrap approach based on the dispersive representation of the amplitude and machine learning’s gradient descent algorithms, they offer a new method to explore the space of consistent S-matrices. We derive bounds on the values of the first two low-energy Taylor coefficients of the amplitude and characterize the resulting amplitudes that populate the allowed region. Crucially, we parallel our neural network analysis with the standard S-matrix bootstrap, both primal and dual, and observe perfect agreement across all approaches.

France

Mehmet Gümüş

Damien Leflot

Piotr Tourkine

Switzerland

Alexander Zhiboedov

The S-matrix bootstrap with neural optimizers. Part I. Zero double discontinuity

It is straightforward to take the gravitational wave solution to first order in <math altimg='si1.svg'><mi>v</mi><mo stretchy='false'>/</mo><mi>c</mi></math> far from a binary source in a Minkowski background and adapt it to the Friedmann-Lemaitre-Robertson-Walker (FLRW) background, representing an expanding isotropic and homogeneous universe. We find the analogous solution for a slightly anisotropic background, which may be a more accurate description of our late universe through which gravitational waves propagate, and implications from tight CMB anisotropy constraints may not necessarily determine the level of anisotropy in the late universe in light of modified gravity models as well as the Hubble tension. We use a perturbative form of the Bianchi I metric and demonstrate how the waveform differs. Using supernova anisotropy data as a reference, we show that the assumption of a Bianchi I background could imply on average a 2.1% difference in inferred luminosity distance compared to what would be inferred under the assumption of the FLRW background. This difference can be as high as 5.9% depending on the observation direction. Therefore, the background spacetime used for the inference of the Hubble parameter from gravitational wave data should be considered carefully.

United States

Kevin J. Ludwick

Peter L. Williams

Inferred Hubble parameter from gravitational waves in a perturbative Bianchi I background

The femtoscopic <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover></math> correlation functions are investigated to predict the signature of the not-yet-established <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3700</mn><mo stretchy="false">)</mo></math> state. Here it is interpreted as a bound state generated by solving the coupled-channel Bethe-Salpeter equations with the local hidden-gauge formalism. We prospect how the relevant properties and observables characterizing this state—like the pole position, scattering lengths and compositeness—might be affected by the variation of the parameters of the model. The amplitudes are then used as input into the momentum correlation functions of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mn>0</mn></msup><msup><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover><mn>0</mn></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>+</mo></msup><msup><mi>D</mi><mo>−</mo></msup></math> pairs. We discuss how their behaviors encode the features of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>X</mi><mo stretchy="false">(</mo><mn>3700</mn><mo stretchy="false">)</mo></math> state.

Brazil

Luciano M. Abreu

Spain

Juan M. Torres-Rincon

Searching for femtoscopic signatures of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>D</mi><mover accent="true"><mi>D</mi><mo stretchy="false">¯</mo></mover></math> (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="normal">I</mi><mrow><mo>=</mo><mn>0</mn></mrow></mrow></math>), X(3700), bound state

We develop a formalism for computing the scattering amplitudes in maximally symmetric de Sitter spacetime with compact spatial dimensions. We describe quantum states by using the representation theory of de Sitter symmetry group and link the Hilbert space to “inertial” geodesic observers. The positive and negative “energy” wavefunctions are uniquely determined by the requirement that in observer's neighborhood, short wavelengths propagate as plane waves with positive and negative frequencies, respectively; they define a unique “Euclidean” (a.k.a. Bunch-Davies) de Sitter invariant vacuum, common to all inertial observers. By following the same steps as in Minkowski spacetime, we show that the scattering amplitudes are given by a generalized Dyson's formula. Compared to the flat case, they describe the scattering of wavepackets with the frequency spectrum determined by geometry. The frequency spread shrinks as the masses and/or momenta become larger than the curvature scale. Asymptotically, de Sitter amplitudes agree with the amplitudes evaluated in Minkowski spacetime.

Poland

Tomasz R. Taylor

United Kingdom

Bin Zhu

Scattering of quantum particles in global de Sitter spacetime I: The formalism

We consider a generic class of effective quantum field theories with arbitrary gauge groups and scalar matter fields. In such theories, we derive the one-loop Renormalization Group Equations (RGEs) for the physical dimension-six operators. The present paper is the first one in a series that is going to cover theories with spin- $$ \frac{1}{2} $$ matter fields, too, including the phenomenologically most relevant SMEFT and LEFT cases. Our present approach provides tools for deriving the yet unknown two-loop RGEs in the SMEFT.

Mikołaj Misiak

Ignacy Nałȩcz

One-loop renormalization group equations in generic effective field theories. Part I. Bosonic operators

The influence of a dark energy fluid on the equation of state of neutron stars is investigated. A detailed analysis is conducted for such models, including the computation of the moment of inertia, the quadrupole moment, and the tidal Love number. The results demonstrate that these quantities are interconnected through the well-known equation of state independent I-Love-Q relations. This work extends the applicability of these universal relations to a broader class of neutron star models.

Simone D’Onofrio

I-Love-Q relations for neutron stars with dark energy

We study the discovery potential for a light Higgs boson via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>g</mi><mi>g</mi><mo stretchy="false">→</mo><msub><mrow><mi>H</mi></mrow><mrow><mi>SM</mi><mtext>−</mtext><mi>like</mi></mrow></msub><mo stretchy="false">→</mo><mi>h</mi><mi>h</mi><mo stretchy="false">→</mo><mi>b</mi><mover accent="true"><mrow><mi>b</mi></mrow><mrow><mo stretchy="false">¯</mo></mrow></mover><mi>γ</mi><mi>γ</mi></mrow></math> process at the Large Hadron Collider (LHC). Focusing on the 2-Higgs Doublet Model Type-I, which can accommodate light neutral Higgs states, of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">O</mi><mo stretchy="false">(</mo><mn>100</mn><mo stretchy="false">)</mo><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> or less in mass, while agreeing with theoretical and up-to-date experimental constraints, we explore the feasibility of a light <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-even Higgs state <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi></math> via the largely unexplored final state <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> at Run-3 of the LHC. We further propose a few benchmark points for future searches.

Taiwan

Morocco

A. Arhrib

Sweden

S. Moretti

S. Semlali

C.H. Shepherd-Themistocleous

China

Y. Wang

Q.S. Yan

Probing a 2HDM type-I light Higgs state via <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>H</mi><mrow><mi>SM</mi></mrow></msub><mo stretchy="false">→</mo><mi>h</mi><mi>h</mi><mo stretchy="false">→</mo><mi>b</mi><mover accent="true"><mi>b</mi><mo stretchy="false">¯</mo></mover><mi>γ</mi><mi>γ</mi></math> at the LHC

In this paper, we study the full Higgs branch Hasse diagrams for any given 6d $$ \mathcal{N} $$ = (1$\textit{,}$ 0) SCFTs constructed via F-theory. This can be done by a procedure of determining all the minimal Higgsings on the generalized quivers of the 6d SCFTs. We call this procedure the atomic Higgsing, which can be implemented iteratively. We present our general algorithm with many concrete examples of Hasse diagrams. We also compare our algorithm with the Higgsings determined by the 3d $$ \mathcal{N} $$ = 4 magnetic quivers. For the cases where the magnetic quivers are unitary, we can reproduce the full Hasse diagrams. We also construct the orthosymplectic magnetic quivers from the Type IIA brane systems for some new examples. Our approach, based on F-theory, applies to the known and new orthosymplectic cases, as well as theories that do not have known descriptions in terms of magnetic quivers. We expect our geometry-based approach to help extend the horizon of the RG flows of the 6d SCFTs.

Japan

Jiakang Bao

Hao Zhang

Atomic Higgsings of 6D SCFTs. Part I

We present a complete proof of the Weak Gravity Conjecture in any perturbative bosonic string theory in spacetime dimension $\textit{D}$ ≥ 6. Our proof works by relating the black hole extremality bound to long range forces, which are more easily calculated on the worldsheet, closing the gaps in partial arguments in the existing literature. We simultaneously establish a strict, sublattice form of the conjecture in the same class of theories. We close by discussing the scope and limitations of our analysis, along with possible extensions including an upcoming generalization of our work to the superstring.

Ben Heidenreich

South Korea

Matteo Lotito

Proving the Weak Gravity Conjecture in perturbative string theory. Part I. The bosonic string

We propose an entropy function for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>4</mn></mrow></msub></mrow></math> BPS black holes in M theory with general magnetic charges, resolving in particular a long-standing puzzle about baryonic charges. The entropy function is constructed from a gravitational block defined solely in terms of topological data of the internal manifold. We show that the entropy of twisted black holes can always be reformulated as an <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="script">I</mi></math>-extremization problem—even in cases where existing large-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> field theory computations fail to provide an answer. Furthermore, we correctly reproduce the entropy for a class of known black holes with purely baryonic magnetic charges. Our results offer both a conjecture for the general gravitational block for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><msub><mrow><mi>AdS</mi></mrow><mrow><mn>4</mn></mrow></msub></mrow></math> black holes in M theory and a prediction for the large-<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>N</mi></math> limit of several partition functions whose saddle points have yet to be found.

Seyed Morteza Hosseini

Italy

Alberto Zaffaroni

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi mathvariant="script">I</mi></mrow></math> Extremization with Baryonic Charges