In this study, we investigate a scenario based on the effects of the Loop Quantum Gravity (LQG) on the electromagnetic sector of the Standard Model of Fundamental Interactions and Particle Physics (SM). Starting from a post-Maxwellian version of electromagnetism that includes LQG effects, we derive and discuss the influence of LQG parameters on classical quantities such as the components of the stress-tensor. Furthermore, we inspect the propagation of electromagnetic waves and examine the optical properties of the QED vacuum in this scenario. Among these, we contemplate the combined effect of the LQG parameters and a homogeneous background magnetic field on the propagation of electromagnetic waves by considering issues such as group velocities and refractive indices of the QED vacuum, in detail. Finally, with the aid of the previously analyzed LQG-extended photonic dispersion relations, we re-discuss the kinematics of the Compton effect and conclude that an interesting nonlinear profile emerges in the wavelengths of the incoming and deflected photons.

Brazil

P.A.L. Mourão

G.L.L.W. Levy

J.A. Helayël-Neto

Reassessing aspects of LQG-modified dispersion relations of photons * P. A. L. Mourão is support by CAPES. G. L. L. W. L. Levy is support by the Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ), Grant No. E-26/202.437/2024.

<p>We perform a high-statistics lattice QCD calculation of the low-energy two-nucleon scattering amplitudes. To address discrepancies in the literature, the calculation is performed at a heavy pion mass in the limit that the light quark masses are equal to the physical strange quark mass, <math xmlns="http://www.w3.org/1998/Math/MathML"><mrow><msub><mi>m</mi><mi>π</mi></msub><mo>=</mo><msub><mi>m</mi><mi>K</mi></msub><mo>≃</mo><mn>714</mn><mspace width="0.28em"></mspace><mi>MeV</mi></mrow></math>. Using a state-of-the-art momentum space method, we rule out the presence of a bound di-nucleon in both the isospin 0 (deuteron) and 1 (di-neutron) channels, in contrast with many previous results that made use of compact hexaquark creation operators. To diagnose the discrepancy, we add such hexaquark interpolating operators to our basis and find that they do not affect the determination of the two-nucleon finite-volume spectrum, and thus they do not couple to deeply bound di-nucleons that are missed by the momentum-space operators. Furthermore, we perform a high-statistics calculation of the HAL QCD potential on the same gauge ensembles and find qualitative agreement with our main results. We conclude that di-nucleons do not form bound states at heavy pion masses and that previous identification of deeply bound di-nucleons must have arisen from a misidentification of the spectrum from off-diagonal elements of a correlation function.</p>

Germany

John Bulava

United States

M.A. Clark

Arjun S. Gambhir

Andrew D. Hanlon

Ben Hörz

Bálint Joó

Christopher Körber

Ken McElvain

Aaron S. Meyer

Henry Monge-Camacho

Colin Morningstar

Joseph Moscoso

Amy Nicholson

Switzerland

Fernando Romero-López

Ermal Rrapaj

Andrea Shindler

Sarah Skinner

Pavlos M. Vranas

André Walker-Loud

Di-nucleons do not form bound states at heavy pion mass

Gravitational waves sourced by amplified scalar perturbations are a common prediction across a wide range of cosmological models. These scalar curvature fluctuations are inherently nonlinear and typically non-Gaussian. We argue that the effects of non-Gaussianity may not always be adequately captured by an expansion around a Gaussian field, expressed through nonlinear parameters such as <italic>f</italic> <inf>NL</inf>. As a consequence, the resulting amplitude of the stochastic gravitational wave background may differ significantly from predictions based on the standard quadratic source model routinely used in the literature.

Italy

A.J. Iovino

S. Matarrese

G. Perna

A. Ricciardone

A. Riotto

How well do we know the scalar-induced gravitational waves?

While significant effort has been devoted to precision calculations of the production of two Higgs bosons via gluon fusion, the treatment of their decays in this process has only recently begun to attract attention. It has been found that fixed-order QCD corrections to fiducial di-Higgs decay rates involving the $$b\overline{b }$$ decay channel can be substantial. Considering $$HH\to b\overline{b }\gamma \gamma $$ , we show that such corrections arise predominantly from sensitivity to soft and collinear QCD radiation at fixed order, and that they are largely washed out once parton showers are included.

Jens Braun

Duarte Fontes

Gudrun Heinrich

Do large QCD corrections to di-Higgs decay survive parton showering? A study of $$HH\to b\overline{b }\gamma \gamma $$

Holographic models that consider classical vector fields in a 5-d background provide effective descriptions for heavy vector meson spectra. This is true both in vacuum and a thermal medium, such as quark gluon plasma. However, the manner in which these phenomenological models work is unclear. In particular, what is the role of the fifth dimension, and what is the relation between the holographic 5-d background and physical (4-d) heavy mesons? Hadrons, in contrast to leptons, are composite particles with some internal structure that depends on the energy at which they are observed. In this study, a static meson is represented by a heavy quark-antiquark pair with an interaction described by a Nambu Goto string existing in the same 5-d background that provides field solutions leading to masses and decay constants of charmonium states. The resulting interaction potential is linear for large distances, with a string tension consistent with the effective Cornell potential. Introducing temperature $\textit{T}$ in the background, it is found for the $J/\psi$ case that there is a deconfining transition at some critical value of $\textit{T}$. The obtained results indicate that the 5-d background effectively represents the internal structure of the (static) charmonium (quasi) states.

Nelson R.F. Braga

Yan F. Ferreira

William S. Cunha

Holography and the internal structure of charmonium * The authors are partially supported by CNPq — Conselho Nacional de Desenvolvimento Científico e Tecnologico, by FAPERJ — Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro and by Coordenação de Aperfeiçoamento de Pessoal de Nível Superior — Brasil (CAPES), Finance Code 001

In general yes, but also not quite. It is known that if the Bekenstein-Hawking entropy is replaced by some kind of generalized entropy, then the Bekenstein bound may be grossly violated. In this work, we show that this undesired violation can be avoided if we employ the equivalence between generalized entropy and varying- <italic>G</italic> gravity (GEVAG). In this approach, modifying entropy necessarily also modifies gravity (as one should expect if gravity is indeed inherently tied to thermodynamics), which leads to an effective gravitational &#8220;constant&#8221; <math altimg='si1.svg'><msub><mrow><mi>G</mi></mrow><mrow><mtext>eff</mtext></mrow></msub></math> that is area-dependent, and a thermodynamic energy that is distinct from the ADM mass. We show that a relaxed Bekenstein bound of the form <math altimg='si2.svg'><mi>S</mi><mo>&#10877;</mo><mi>C</mi><mi>R</mi><mi>E</mi></math> is always satisfied, albeit the coefficient <italic>C</italic> is no longer 2 <italic>&#960;</italic>.

China

Hengxin Lü

Yen Chin Ong

Do black holes with generalized entropy violate Bekenstein bound?

It is generally believed that quantum entanglement in the maximally entangled states is greater than quantum entanglement in the non-maximally entangled states under a relativistic setting. In this paper, we study quantum entanglement for four different types of Bell-like states of the fermionic modes near the event horizon of a Schwarzschild black hole. It is interesting to find that quantum entanglement in the maximally entangled states is less than quantum entanglement in the non-maximally entangled states in Schwarzschild spacetime. From the perspective of quantum resources, the non-maximally entangled states may have more advantages in curved spacetime compared to the maximally entangled states. This is obviously different from the conclusions in previous paper. For two types of Bell-like states, quantum entanglement suffers sudden death under the Hawking effect of the black hole, and for the other two types of Bell-like states, quantum entanglement can exist forever regardless of the Hawking temperature. Therefore, we should choose appropriate types of Bell-like states to handle relativistic quantum information tasks.

Shu-Min Wu

Si-Han Li

Do maximally entangled states always have an advantage over non-maximally entangled states in Schwarzschild black hole?

We propose a scenario of a de Sitter universe living on an End-of-the-World brane. Motivated by the Swampland programme and in particular the Cobordism Conjecture, we consider a compact region of AdS nucleating from nothing, with a dS living on its boundary. We show that it can equivalently be interpreted as an up-tunnelling from AdS with cosmological constant Λ → −∞, following Brown and Dahlen’s proposal for ‘nothing’. Their picture naïvely leads to the conclusion that the brane has infinite negative tension. But we show that it becomes finite and positive once we employ holographic renormalization, recovering the Bubble of Something where the domain wall becomes a boundary of spacetime. The same holds true in any number of dimensions and, moreover, at the level of metric perturbations. This provides motivation for alternative routes of obtaining cosmology from quantum gravity or string theory using domain walls, departing from conventional vacuum approaches.

United Kingdom

Benjamin Muntz

Antonio Padilla

Paul Saffin

Do we live on the End of the World?

The Bekenstein–Hawking equation states that black holes should have entropy proportional to their areas to make black hole physics compatible with the second law of thermodynamics. However, this equation leads to an inconsistency among the first law of black hole mechanics, the entropy conservation law of quantum mechanics, and a heuristic picture for Hawking radiation—creation of entangled pairs near the horizon. Here we propose an equation alternative to the Bekenstein–Hawking equation from the viewpoint of quantum information, to resolve this inconsistency without changing Hawking’s original pair-creation picture for the radiation. This argues that the area of any stationary black hole, including Kerr and charged ones, is proportional to the coherent information—which is “minus” the conditional entropy defined only in the quantum regime—from the outside, to the black hole excluding negative-frequency particles generated by Hawking’s pair creation. Our equation suggests that negative-frequency particles inside a black hole behave as if they have “negative” entropy. Our result implies that a black hole stores purely quantum information, rather than classical information, and the area of the event horizon describes the number of Bell pairs that can be distilled between the interior and exterior.

Japan

Koji Azuma

Sathyawageeswar Subramanian

Go Kato

Do Black Holes Store Negative Entropy?

We propose a simple model to obtain a sizable muon anomalous magnetic dipole moment (muon $ g-2 $ ) that introduces several $ S U(2)_L $ multiplet fields without any additional symmetries. The neutrino mass matrix is simply induced via a type-II seesaw scenario in terms of $ S U(2)_L $ triplet Higgs with $ U(1)_Y $ hypercharge 1. In addition, we introduce an $ S U(2)_L $ quartet vector-like fermion with hypercharge $ 1/2 $ and scalar with hypercharge $ 3/2 $ . The quartet fermion plays a crucial role in explaining muon $ g-2 $ causing the chiral flip inside a loop diagram with the mixing of triplet and quartet scalar bosons via the standard model Higgs. We conduct a numerical analysis and search for the allowed region in our parameter space and demonstrate the collider physics.

Takaaki Nomura

Hiroshi Okada

Muon $\textit{g}$ − 2 with $\textit{SU}$(2) $\textit{L}$ multiplets * This research was supported by an appointment to the JRG Program at the APCTP through the Science and Technology Promotion Fund and Lottery Fund of the Korean Government, the Korean Local Governments - Gyeongsangbuk-do Province and Pohang City (H.O.), and the Fundamental Research Funds for the Central Universities (T. N.)