This article explores how modifications to gravity influence the structure of the brane, with the goal of identifying the gravitational model that most closely reflects the one governing our physical universe. To achieve this, we consider a generalization of standard General Relativity. The stability of the model is evaluated through probabilistic measurements, revealing minimum points that represent the most probable and stable configurations of the brane for different values of the gravitational terms. Furthermore, the location of fermions on the brane is affected by gravitational variations, with the presence of resonance modes and the possibility of leakage of massive fermions into the bulk. Numerical analyses are presented, showing that the increase in the influence of gravitational terms increases the certainty of the location of massless fermions on the brane. All these results provide important insights for understanding the dynamics of the braneworld universe.

China

Brazil

A.R.P. Moreira

Mexico

Shi-Hai Dong

Braneworld- <italic>f</italic>( <italic>R</italic>, <italic>T</italic>, <italic>G</italic>)

In this paper, we investigate pure geometric <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> cosmology branes embedded in five-dimensional spacetime. The form of <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo stretchy='false'>)</mo></math> is chosen as a polynomial. The Five-dimensional scalar curvature <italic>R</italic> is assumed to be constant. Based on the value of the four-dimensional cosmological constant <math altimg='si2.svg'><msub><mrow><mi>&#955;</mi></mrow><mrow><mn>4</mn></mrow></msub></math>, the branes can be classified into Minkowski, de Sitter, and de anti-de Sitter cases. Solutions for each case can be calculated. These solutions are stable against linear tensor perturbations in all cases. In the Minkowski brane case, the zero mode of gravity can be localized on the brane. In the de Sitter brane case, the zero mode and one massive Kaluza-Klein mode can be localized on the brane. In the anti-de Sitter brane case, all massive Kaluza-Klein modes can be localized on the brane. The results of the analysis of tensor fluctuations are the same in both the Einstein frame and the Jordan frame.

Heng Guo

Cai-Ling Wang

Yong-Tao Lu

Yue Sun

Lang-Lang Wang

Pure geometric <italic>f</italic>( <italic>R</italic>) branes

This study explores wormhole solutions within two distinct modified gravity theories, namely <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math> gravity and <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math> gravity, incorporating Bose-Einstein condensate (BEC) dark matter to analyze their geometric properties. The primary objective is to comprehensively compare wormhole characteristics in these frameworks under the influence of BEC matter. The derived shape functions satisfy all fundamental traversability conditions. Furthermore, we examine the energy conditions, revealing that the NEC holds in <math altimg='si1.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>R</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math> gravity but is violated in <math altimg='si2.svg'><mi>f</mi><mo stretchy='false'>(</mo><mi>Q</mi><mo>,</mo><mi>T</mi><mo stretchy='false'>)</mo></math> gravity, highlighting the contrasting nature of wormhole solutions in these theories. Additionally, we investigate the effects of anisotropy, active gravitational mass, and surface diagram of wormhole geometries. Our findings confirm the existence of physically viable and stable wormhole models within these modified gravity theories.

India

Chaitra Chooda Chalavadi

H. Aruna Kumara

V. Venkatesha

Probing the geometries of wormholes: A comparative study of <italic>f</italic>( <italic>R</italic>, <italic>T</italic>) and <italic>f</italic>( <italic>Q</italic>, <italic>T</italic>) theories in the presence of BEC matter

Gravitational particle production in cosmology is a mechanism through which particles of different natures are produced during the very early universe. It is a general mechanism that explains how the universe became populated with the particles of the Standard Model after cosmic inflation and may also account for the origin of dark matter. In this work, we study the non-perturbative production of massive scalar particles in the Higgs- $$R^2$$ inflation model, a two-field scalar inflation model within the Einstein frame. We consider spectator scalar fields that are conformally or minimally coupled to the gravitational field through the curvature scalar $\textit{R}$ which in turn is a time-dependent function determined by the fields driving inflationary dynamics. We numerically compute the production of these particles using the Bogolyubov transformation method for each scenario, aiming to assess the spectrum of the produced particles. For both scenarios, we consider light particles with masses $$m_\chi \ll H_{\textrm{end}}$$ and large masses that exceed the Hubble scale at the end of inflation $$m_\chi \gtrsim H_{\textrm{end}}.$$ We use these numerical results to calculate the relic abundance $$\Omega _\chi h^2$$ to find out if the model is viable as a dark matter candidate.

Flavio Pineda

Luis Pimentel

Non-perturbative approach for scalar particle production in Higgs- $$R^2$$ inflation

The hybrid metric-Palatini gravity with Lagrangian density $$L =R+f(\mathcal {R},\mathcal {R}_{\mu \nu }\mathcal {R}^{\mu \nu })$$ is considered, where $\textit{R}$ is the metric Ricci scalar and $$\mathcal {R}_{\mu \nu }$$ is the Palatini Ricci tensor. Contrary to the standard hybrid metric-Palatini theory, because of the term $$\mathcal {R}_{\mu \nu }\mathcal {R}^{\mu \nu }$$ in the action, the model can not be analytically transformed to a scalar-tensor theory. However, on top of a maximally symmetric space-times like the FRW universe, there is a way to solve for a metric compatible connection which we will follow in this paper. The cosmological implications of the resulting model will then be fully considered. The best fit values of the model and cosmological parameters will be obtained by confronting the model with the recent observational data on the Hubble parameter. We will see that the observational data can be explained very good in this model, but, significant deviations from the standard $$\Lambda $$ CDM model could be seen in derivatives of the Hubble parameter $\textit{q}$, $\textit{j}$ and $\textit{s}$. We will perform a statefinder analysis for the model and show that its behavior differs from that of the $$\Lambda $$ CDM model. Also, we will consider the recently proposed $\textit{Om}$ diagnostics to categorize the dark energy type of the model and obtain the $$\omega $$ -varying alternative of the model that mimics the Hubble flow.

Iran

Shahab Shahidi

Shiva Kayedi

Cosmological implications of hybrid metric-Palatini $$f(\mathcal {R},\mathcal {R}_{\mu \nu }\mathcal {R}^{\mu \nu })$$ gravity

We investigate the classical and quantum dynamics of $\textit{f}$($\textit{R}$) gravity’s rainbow in the presence of a perfect fluid, employing Schutz’s formalism to establish a well-defined notion of time. In the classical regime, we derive and solve the equations of motion, obtaining both analytical and numerical solutions. Through canonical quantisation, we formulate the Schrödinger–Wheeler–DeWitt (SWD) equation for the quantum model. By solving its eigenfunctions, we construct the wave function of the Universe and obtain analytical solutions in scenarios dominated by stiff matter. Our results highlight the impact of rainbow gravity on quantum evolution, particularly in modifying the structure of the wave function and shaping the transition from the quantum to the classical regime.

Chile

Andrés Burton-Villalobos

Giovanni Otalora

Manuel Gonzalez-Espinoza

Yoelsy Leyva

Classical and quantum cosmology of $\textit{f}$($\textit{R}$) gravity’s rainbow in Schutz’s formalism

We perform a detailed study of the current phenomenological status of baryon number violating operators within the framework of the $\textit{R}$-parity violating Minimal Supersymmetric Standard Model (RPV-MSSM). This study aims to identify any gaps in the experimental coverage of the RPV landscape. We identify the unique final states for all possible LSPs decaying via four different benchmark UDD operators. Both the direct production of the LSP and its production via gauge-cascades are considered. For each LSP, we assume that only one UDD coupling is non-zero at a time and confront the signals with existing ATLAS and CMS searches implemented in the recasting framework CheckMATE 2. We find that the UDD colored LSP sector is well covered with the mass bounds on the gluino LSP being the strongest, and with possible improvements for some of the right-handed squark LSPs. We also point out that there is limited coverage for electroweakino and slepton LSPs with UDD decays. This limitation may be due to the lack of targeted experimental searches for these specific final states or the appropriate recasting of existing searches.

Germany

Herbi Dreiner

United States

Michael Hank

Sweden

Yong Koay

Martin Schürmann

Rhitaja Sengupta

Apoorva Shah

Nadja Strobbe

Evelyn Thomson

The ABC of RPV. Part II. Classification of R-parity violating signatures from UDD couplings and their coverage at the LHC

The detection of primordial B-modes, a key probe of cosmic inflation, is increasingly challenged by contamination from weak gravitational lensing B-modes induced by large-scale structure (LSS). We present a delensing pipeline designed to enhance the sensitivity to the inflationary parameter $\textit{r}$, minimizing reliance on foreground mitigation during lensing reconstruction. Using simulations of Simons Observatory-like CMB observations and $\textit{Euclid}$-like LSS surveys in the Northern hemisphere, we demonstrate that excluding low- $$\ell $$ modes ( $$\ell <200$$ ) effectively mitigates foreground biases, enabling robust lensing potential reconstruction using observed CMB polarization maps. We reconstruct the lensing potential with a minimum-variance (MV) quadratic estimator (QE) applied to CMB polarization data and combine this with external LSS tracers to improve delensing efficiency. Two complementary methods – the gradient-order template and the Inverse-lensing approach – are used to generate lensing B-mode templates, which are cross-correlated with observed B-modes. This achieves a 40% reduction in the uncertainty of r with CMB-only reconstruction, improving to 60% when incorporating external LSS tracers. We validate our results using both the Hamimeche and Lewis likelihood and a Gaussian approximation, finding consistent constraints on $\textit{r}$. Our work establishes a streamlined framework for ground-based CMB experiments, demonstrating that synergies with LSS surveys significantly enhance sensitivity to primordial gravitational waves.

Wen-Zheng Chen

Yang Liu

Yi-Ming Wang

Hong Li

Delensing for precision cosmology: optimizing future CMB B-mode surveys to constrain $\textit{r}$

Recent searches by the CMS collaboration at the Large Hadron Collider (LHC) in the ‘diphoton plus <math altimg='si1.svg'><mi>b</mi><mover accent='true'><mrow><mi>b</mi></mrow><mrow><mo stretchy='false'>&#175;</mo></mrow></mover></math> final state&#8217; have revealed an excess near 650 GeV, which might indicate the presence of a (broad) heavy resonance decaying into a Standard Model (SM) Higgs boson and an additional particle. At the same time, both ATLAS and CMS as well as all experiments at the Large Electron-Position (LEP) collider have reported excesses consistent with a light Higgs boson channel around 95 GeV, suggesting a potential connection between these two signals. In this study, we investigate these anomalies within the context of the CP-conserving 2-Higgs-Doublet Model (2HDM) Type III. In our proposed scenario, a heavy CP-odd Higgs boson <italic>A</italic> with a mass near 650 GeV decays into a SM-like Higgs boson <italic>H</italic> and a <italic>Z</italic> boson, with the <italic>H</italic> boson subsequently decaying into diphotons and the <italic>Z</italic> boson decaying into <math altimg='si1.svg'><mi>b</mi><mover accent='true'><mrow><mi>b</mi></mrow><mrow><mo stretchy='false'>&#175;</mo></mrow></mover></math> pairs. To explain the excess around 95 GeV, we independently select the mass of the light CP-even Higgs boson of the model <italic>h</italic> to be around this value. This configuration allows for a consistent explanation of both the high- and low-mass excesses observed in the experiments. Through a detailed analysis, we demonstrate that these two signals can be fitted simultaneously at the 2.5 <italic>&#963;</italic> significance level, offering a promising solution to the observed anomalies and potentially hinting at new physics Beyond the Standard Model (BSM).

Morocco

R. Benbrik

Poland

M. Boukidi

K. Kahime

United Kingdom

S. Moretti

L. Rahili

B. Taki

Exploring potential Higgs resonances at 650 GeV and 95 GeV in the 2HDM Type III

Polarization is a prominent feature of gravitational wave observations and can be used to distinguish between different modified gravity theories. Compared to General Relativity, $\textit{f}$($\textit{R}$) gravity exhibits an additional polarization originating from a scalar field, which is a combination of the longitudinal and breathing modes. When the scalar mass of $\textit{f}$($\textit{R}$) is zero, the mixed mode will reduce to a pure breathing mode with the disappearance of the longitudinal mode. However, this reducing seems to be disallowed because a positive scalar mass is often required to maintain the stability of the cosmological perturbation. In fact, the massless scalar case can provide a stable perturbation, but more detailed constraints need to be considered. For the completeness of the polarization analysis, we explore the possibility that there are stable massless scalar polarizations in viable dark energy $\textit{f}$($\textit{R}$) models. We find that the existence of stable massless scalar polarization depends on the structure of $\textit{f}$($\textit{R}$) model and can be used to distinguish different models in $\textit{f}$($\textit{R}$) gravity.

Xin-Dong Du

Peng-Cheng Li

Stable massless scalar polarization of $\textit{f}$($\textit{R}$) gravity