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

Switzerland

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.

Germany

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.

Brazil

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.)

<p>Recent measurements of the CMS experiment at the LHC show possibly, with about <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mn>3</mn><mi>σ</mi></math> significance, a resonance in diphoton events with an invariant mass of 95.4 GeV. If this resonance can be confirmed, this could be a hint for a new elementary particle beyond the Standard Model. An additional Standard-model-like Higgs boson with this mass could be excluded by the CMS experiment. We investigate whether this resonance could fit into a two-Higgs-doublet model highly constrained by <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math> symmetry, the so-called maximally <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-symmetric model (MCPM). In the strict symmetry limit of the MCPM only the fermions of the third generation obtain masses. We discuss a mechanism where the first and second generation fermions get masses through effects from interactions with very high mass particles. The latter can be integrated out at Large Hadron Collider (LHC) energies giving effective Lagrangian terms, among them these mass terms. This procedure also gives us a Cabibbo-Kobayashi-Maskawa (CKM) matrix which automatically satisfies some salient structural features observed in experiments. We call the resulting theory MCPM’. Our finding shows that indeed the enhancement measured by CMS could originate from the pseudoscalar Higgs boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>h</mi><mo>′′</mo></msup></math> of this model. According to the model the boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>h</mi><mo>′′</mo></msup></math> would mainly be produced in the Drell-Yan reaction by charm-anticharm-quark fusion. The main decay mode of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>h</mi><mo>′′</mo></msup></math> is predicted to be <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>h</mi><mo>′′</mo></msup><mo stretchy="false">→</mo><mi>c</mi><mover accent="true"><mi>c</mi><mo stretchy="false">¯</mo></mover></math>. We then consider the so called oblique parameters <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi></math> which give us an allowed region for the mass of the scalar Higgs boson <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>h</mi><mo>′</mo></msup></math> versus that of the charged ones <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup></math> of the MCPM’. We calculate the effect of these charged bosons <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup></math> in the leptonic decays of the charm mesons <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>D</mi><mo>±</mo></msup></math> and the charm-strange mesons <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>D</mi><mi>s</mi><mo>±</mo></msubsup></math>. Our results indicate that the mass <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><msup><mi>H</mi><mo>±</mo></msup></msub></math> of the charged Higgs bosons <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>H</mi><mo>±</mo></msup></math> of the MCPM’ should be around 300 GeV.</p>

Chile

M. Maniatis

O. Nachtmann

CMS results for the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>γ</mi><mi>γ</mi></mrow></math> production at the LHC: Do they give a hint for a Higgs boson of the maximally <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>C</mi><mi>P</mi></mrow></math> symmetric two-Higgs-doublet model?

<p>Nucleophobic axion models, wherein axion couplings to both protons and neutrons are simultaneously suppressed, can relax the stringent constraints from SN 1987A. However, it remains uncertain whether these models maintain their nucleophobic property under the influence of finite baryon density effects. These are especially relevant in astrophysical environments near saturation density, such as supernovae (SNe). In this study, we demonstrate that the nucleophobic solution remains viable also at finite density. Furthermore, we show that the SN axion bound relaxes significantly in nucleophobic models, even when accounting for the integration over the nonhomogeneous environment of the SN core.</p>