We introduce a novel level crossing phenomenon in the mass mixing between QCD axions: one canonical QCD axion and one $ Z_{{\cal{N}}} $ axion. The level crossing can occur at or slightly before the QCD phase transition critical temperature, depending on the ratio of the axion decay constants, $ \sim 1.69 $ . The cosmological evolution of the mass eigenvalues in these two scenarios is similar; however, the transition of axion energy density differs significantly. Finally, we estimate the relic density of the QCD axion dark matter in this context. Additionally, this level crossing may have some interesting cosmological implications.

China

Hai-Jun Li

Yu-Feng Zhou

Mass mixing between QCD axions * Supported by the CAS Project for Young Scientists in Basic Research YSBR-006, the National Key R&D Program of China (2017YFA0402204), and the National Natural Science Foundation of China (11821505, 11825506, 12047503)

This study investigates the intrinsic electric dipole moment (EDM) of the $\textit{τ}$ lepton, which is an important quantity in the search for physics beyond the Standard Model (BSM). In preparation for future measurements at the Super Tau-Charm Facility (STCF), we employ Monte Carlo simulations of the $ e^+e^- \rightarrow \tau^+\tau^- $ process and optimize the analysis methodology for EDM extraction. Machine learning techniques are implemented to efficiently identify signal events ( $ \tau^\pm\rightarrow \pi^\pm\pi^0\nu_\tau $ ), which result in a significant improvement in signal-to-noise ratio. Our optimized event selection algorithm achieves 80.0% signal purity with 6.3% efficiency. We develop an analytical approach for $\textit{τ}$ lepton momentum reconstruction and derive the squared spin density matrix along with optimal observables, which maximize the sensitivity to $ d_\tau $ . The relationship between these observables and the EDM is established with the estimated sensitivity of $ |d_\tau| \lt 3.89\times 10^{-18}\,e\cdot\mathrm{cm} $ at a 68% confidence level. These results provide a foundation for future experimental measurements of the $\textit{τ}$ lepton EDM in STCF experiments.

Xulei Sun

Yongcheng Wu

Xiaorong Zhou

Sensitivity study of the tau lepton electric dipole moment at the Super Tau-Charm Facility * Supported by the National Key R&D Program of China (2022YFA1602200, 2023YFA1607200); the National Natural Science Foundation of China (NSFC) (12341501, 12341503, 12341504); the international partnership program of the Chinese Academy of Sciences (211134KYSB20200057). Xulei Sun is supported by the Undergraduate Research Program of the University of Science and Technology of China and the Xinhe Scholar Program of the School of the Gifted Young

We use a modified relativistic quark model to study the properties of excited charmed and charmed strange mesons. We calculate the masses and wave functions of conventional charmed and charmed strange mesons incorporating both spin and $\textit{S}$-$\textit{D}$ mixing effects and fit parameters of the potential model with known experimental states using differential evolution techniques. Using leading Born-Oppenheimer expansion, we compute the spectrum and wave functions of the first gluonic excited state of charmed and charmed strange mesons. We examine the effects of gluonic excitation on the spectrum of the resulting hybrid mesons. Using our calculated spectrum and wave functions, we determine the radiative transitions of the conventional and hybrid open charm mesons. We compare our calculations with experimental data and other works. We expect our results will be beneficial in the detection of charmed and charmed strange conventional and hybrid mesons.

Pakistan

Saba Noor

Faisal Akram

Bilal Masud

Study of excited $\textit{D}$ and D$_{s}$ mesons in a relativized quark model * F. A. acknowledges HEC grant 20-15728/NRPU/R&D/HEC/2021, Pakistan

We discuss the landscape of flavor physics at the Circular Electron-Positron Collider (CEPC), based on the nominal luminosity outlined in its Technical Design Report. The CEPC is designed to operate in multiple modes to address a variety of tasks. At the $\textit{Z}$ pole, the expected production of 4 Tera $\textit{Z}$ bosons will provide unique and highly precise measurements of $\textit{Z}$ boson couplings, while the substantial number of boosted heavy-flavored quarks and leptons produced in clean $\textit{Z}$ decays will facilitate investigations into their flavor physics with unprecedented precision. We investigate the prospects of measuring various physics benchmarks and discuss their implications for particle theories and phenomenological models. Our studies indicate that, with its highlighted advantages and anticipated excellent detector performance, the CEPC can explore beauty and $\textit{τ}$ physics in ways that are superior to or complementary with the Belle II and Large-Hadron-Collider-beauty experiments, potentially enabling the detection of new physics at energy scales of 10 TeV and above. This potential also extends to the observation of yet-to-be-discovered rare and exotic processes, as well as testing fundamental principles such as lepton flavor universality, lepton and baryon number conservation, etc., making the CEPC a vibrant platform for flavor physics research. The $\textit{WW}$ threshold scan, Higgs-factory operation and top-pair productions of the CEPC further enhance its merits in this regard, especially for measuring the Cabibbo-Kobayashi-Maskawa matrix elements, and Flavor-Changing-Neutral-Current physics of Higgs boson and top quarks. We outline the requirements for detector performance and considerations for future development to achieve the anticipated scientific goals. The role of machine learning for innovative detector design and advanced reconstruction algorithms is also stressed. The CEPC flavor physics program not only develops new capabilities for exploring flavor physics beyond existing projects but also enriches the physics opportunities of this machine. It should be remarked that, given the richness of the CEPC flavor physics, this manuscript is not meant to be a comprehensive survey, but rather an investigation of representative cases. Uncovering the full potential of flavor physics at the CEPC will require further dedicated explorations in the future.

Xiaocong Ai

United States

Wolfgang Altmannshofer

Peter Athron

Xiaozhi Bai

Lorenzo Calibbi

Germany

Lu Cao

Yuzhi Che

Chunhui Chen

Ji-Yuan Chen

Long Chen

Mingshui Chen

Shanzhen Chen

Xuan Chen

Shan Cheng

Cheng-Wei Chiang

Switzerland

Andreas Crivellin

Hanhua Cui

France

Olivier Deschamps

Sébastien Descotes-Genon

Xiaokang Du

Shuangshi Fang

Yu Gao

Yuanning Gao

Li-Sheng Geng

Pablo Goldenzweig

Jiayin Gu

Feng-Kun Guo

Yuchen Guo

Zhi-Hui Guo

Tao Han

Hong-Jian He

Jibo He

Miao He

Xiaogang He

Yanping Huang

Gino Isidori

Quan Ji

Jianfeng Jiang

Xu-Hui Jiang

Slovenia

Jernej F. Kamenik

Tsz Hong Kwok

Gang Li

Geng Li

Haibo Li

Haitao Li

Hengne Li

Honglei Li

Liang Li

Lingfeng Li

Qiang Li

Shu Li

Xiaomei Li

Xin-Qiang Li

Yiming Li

Yubo Li

Yuji Li

Zhao Li

Hao Liang

Zhijun Liang

Libo Liao

Zoltan Ligeti

Jia Liu

Jianbei Liu

Tao Liu

Yi Liu

Yong Liu

Zhen Liu

Xinchou Lou

Peng-Cheng Lu

Italy

Alberto Lusiani

Hong-Hao Ma

Kai Ma

Farvah Mahmoudi

Yajun Mao

Yaxian Mao

David Marzocca

Juan-Juan Niu

Soeren Prell

Huirong Qi

Sen Qian

Zhuoni Qian

Qin Qin

Ariel Rock

Jonathan L. Rosner

Manqi Ruan

Dingyu Shao

Chengping Shen

Xiaoyan Shen

Haoyu Shi

United Kingdom

Liaoshan Shi

Zong-Guo Si

Cristian Sierra

Huayang Song

Shufang Su

Wei Su

Zhijia Sun

Michele Tammaro

Dayong Wang

En Wang

Flavor physics at the CEPC: a general perspective * We acknowledge financial support from the National Natural Science Foundation of China (NSFC) (12125507, 12047503, 12035008, 2211530479, 12475094, 12135006, 12075097, 12375086, 2022YFA1601903, 12061141007, 12375091, 12342502, 12235018, 12335003, 12105100, 12475106, 11961141015, 12188102, 12175245, 12205171, 12321005, tsqn202312052, 2024HWYQ-005, 12405121, 12447167, 12061141006, 12405102, 12125503,12305115, 12075213, 12335005, 12235008); the Chinese Academy of Sciences (YSBR-101, XDB34030000); the National Key R&D Program of China (2022YFE0116900, 2023YFA1606703, 2022YFA1601901); the National Key Research and Development Program of China (2023YFA1606300); the Excellent Postdoctoral Program of Jiangsu Province (2023ZB891); the Shenzhen Science and Technology Program (202206193000001, 20220816094256002); the Natural Science Foundation for Distinguished Young Scholars of Henan Province (242300421046); the Beijing Municipal Natural Science Foundation (JQ22002); the Area of Excellence (AoE/P-404/18-3) and the General Research Fund (16304321) (both grants are issued by the Research Grants Council of Hong Kong S.A.R); the MOST National Key R&D Program (2023YFA1606303); the Shanghai Key Laboratory for Particle Physics and Cosmology, Key Laboratory for Particle Astrophysics and Cosmology (Ministry of Education), Shanghai Jiao Tong University

In this article we propose the scheme of integration of two-dimensional $\textit{F}$($\textit{R}$) gravity vacuum equations in a travelling wave variable. The main emphasis is placed on the fundamental possibility of obtaining different forms of the function $\textit{F}$($\textit{R}$) by arbitrarily choosing a certain function through which all components of the metric tensor of the theory can be expressed.

Russia

Maria Shubina

Scheme of integration of vacuum $\textit{F}$($\textit{R}$) gravity in a travelling wave variable

<p>We numerically evaluate, for slab entangling geometries, the mutual information and the holographic entanglement entropy between strongly interacting fields in different spatial regions for two different conformal holographic models at finite temperature and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>R</mi></math>-charge density. The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>1</mn><mrow><mi>R</mi></mrow></mrow></math>-Charge Black Hole (1RCBH) model describes a strongly interacting fluid with a critical point in its phase diagram, while the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mn>2</mn><mrow><mi>R</mi></mrow></mrow></math>-Charge Black Hole model has no critical point. In both models, we find that the mutual information tends to be overall reduced by increasing the value of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo>/</mo><mi>T</mi></math> at larger values of the separation length <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math> between two disjoint spatial regions of the medium, while the opposite tendency is observed at lower values of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>x</mi></math>. We also observe that, very close to the critical point of the 1RCBH model, the mutual information tends to increase with increasing <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo>/</mo><mi>T</mi></math> in the stable branch of black hole solutions. Moreover, the mutual information between the fields in the two disjoint regions is observed to be enhanced by increasing the characteristic size <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>ℓ</mo></math> of these regions, with such an enhancement asymptotically saturating, thus suggesting the existence of a finite field correlation length between the disjoint regions of the system. The finite part of the entanglement entropy may change sign depending on the values of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>μ</mi><mo>/</mo><mi>T</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>ℓ</mo></math>, and it correctly detects the critical point of the 1RCBH model, a feature that is also adequately detected by the mutual information.</p>

Brazil

Gustavo de Oliveira

Ronaldo F. Costa

Lucas C. Céleri

Romulo Rougemont

Mutual information and holographic entanglement entropy for strongly coupled <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>R</mi></mrow></math>-charged plasmas

We construct an analytic $\textit{f}$($\textit{R}$) gravity model that unifies early-time inflation with late-time cosmic acceleration within a single covariant framework. At high curvature, the model reproduces a Starobinsky-like inflationary plateau, while at low curvature it asymptotes to a stable dark energy-dominated phase. In the scalar-tensor representation, this construction yields a hilltop-type potential in the Jordan frame, which maps to an exponential potential in the Einstein frame. To account for radiative effects, we introduce a logarithmic correction to the Einstein-frame potential inspired by one-loop effective field theory, producing a late-time flattening without requiring fine-tuning. The resulting scalaron dynamics reduce the effective mass to $$\mathcal {O}(H_0)$$ , inducing a thawing regime that deviates from a cosmological constant at the sub-percent levels. A joint background likelihood analysis using Pantheon+SH0ES and BAO+CC datasets (within the CPL parametrization) yields $$H_0 = 73.4 \pm 0.6$$ km/s/Mpc and $$\Omega _m = 0.253 \pm 0.007$$ , consistent with local expansion rate measurements. The best-fit scalar field parameters are $$\varphi _0 \approx 0.027\,M_\textrm{Pl}$$ and $$\lambda \approx 0.010\,M_\textrm{Pl}$$ , corresponding to a present-day dark energy equation of state $$w_0 \approx -0.985$$ . While compatible with $$\Lambda $$ CDM within current observational bounds, the model satisfies GR recovery at low curvature and exhibits attractor-like behavior, thereby minimizing sensitivity to initial conditions.

India

M. Pradosh Keshav

Arun Kenath

Loop-corrected scalar potentials and late-time acceleration in $$f(R)$$ gravity

In this paper, we present intriguing traversable and asymptotically flat wormhole solutions within <math altimg='si18.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi>L</mi><mi>m</mi></msub><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity. We integrate our model with the gravitational analog of the Schwinger effect, describing the emergence of particle-antiparticle pairs from the vacuum. By introducing a fundamental minimal length via the generalized uncertainty principle, we establish critical constraints on matter distribution and spacetime structure. Our findings reveal how this fundamental length shapes the wormhole geometry, steepening the slope toward the throat and mitigating violations of the weak and null energy conditions. This adjustment allows the supporting matter to avoid phantom behavior at the Planck scale, suggesting a more stable configuration. We also explore the intriguing effects of gravitational lensing, showing that these exotic wormholes repel light rather than capture it. For <math altimg='si9.svg'><mi>&#946;</mi></math> values ranging from 0 to 45, the deflection angle remains negative for all corresponding <math altimg='si14.svg'><mrow><mi>&#945;</mi><mo>(</mo><msub><mi>r</mi><mrow><mi>t</mi><mi>p</mi></mrow></msub><mo>)</mo></mrow></math> values, indicating a repulsive gravitational force that pushes photons away from the throat. Moreover, the forces acting on the wormhole exhibit a delicate balance, demonstrating equal strength in opposing directions&#8211;an essential feature of stability. The complexity factor <math altimg='si17.svg'><msub><mi>Y</mi><mrow><mi>T</mi><mi>F</mi></mrow></msub></math> decreases with distance from the throat, indicating that corrections from the generalized uncertainty principle are most significant near the throat and diminish outward. Overall, our work highlights the allure of these wormhole geometries and the pivotal role of quantum effects in their formation, paving new avenues for understanding gravity and spacetime.

South Africa

Azerbaijan

A. Errehymy

Uzbekistan

B. Turimov

Kazakhstan

A. Syzdykova

K. Myrzakulov

Saudi Arabia

N. Alessa

A.H. Abdel-Aty

Dymnikova-Schwinger GUP-corrected wormholes in <math altimg='si18.svg'><mrow><mi>f</mi><mo>(</mo><mi>R</mi><mo>,</mo><msub><mi>L</mi><mi>m</mi></msub><mo>,</mo><mi>T</mi><mo>)</mo></mrow></math> gravity

We investigate a novel realization of warm inflation driven by the Standard Model (SM) Higgs field within the Palatini formulation of gravity, supplemented by an $$R^2$$ curvature correction. By incorporating dissipative dynamics and a thermal radiation bath, our model eliminates the need for a separate reheating phase and naturally flattens the inflationary potential. We derive the slow-roll dynamics in the strong dissipation regime, compute the resulting inflationary observables, and demonstrate compatibility with the latest CMB constraints from Planck, BICEP/Keck, and BAO data. Specifically, we show that the scalar spectral index $$n_s$$ lies in the range 0.963–0.965, and the tensor-to-scalar ratio $\textit{r}$ is strongly suppressed, $$r \sim \mathscr {O}(10^{-3}$$ – $$10^{-2})$$ , for Higgs quartic couplings $$\lambda \sim 10^{-9}$$ . These predictions remain robust under two distinct growing-mode functions. Furthermore, we show that the model is consistent with the refined de Sitter swampland conjecture due to entropy production during inflation. This work represents the first comprehensive study of warm minimal Higgs inflation in Palatini $$R^2$$ gravity, unifying quantum gravity criteria, thermal field dynamics, and observational consistency within a single inflationary framework.

Thailand

Jureeporn Yuennan

Ratbay Myrzakulov

P. Sahoo

Farruh Atamurotov

Phongpichit Channuie

Minimal warm higgs inflation in palatini $$R^{2}$$ gravity

We examine inflationary models in the <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 framework where we have a conformal constant and an <italic>RT</italic>-mixing term apart from an R term. The RT-mixing term introduces non-minimal coupling between gravity and matter. We consider the exponential SUSY potential <math altimg='si2.svg'><mi>V</mi><mo stretchy='false'>(</mo><mi>&#981;</mi><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><msup><mrow><mi>M</mi></mrow><mrow><mn>4</mn></mrow></msup><mrow><mo stretchy='true'>(</mo><mn>1</mn><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><msup><mrow><mi>e</mi></mrow><mrow><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mi>&#955;</mi><mi>&#981;</mi><mo stretchy='false'>/</mo><msub><mrow><mi>M</mi></mrow><mrow><mi>p</mi><mi>l</mi></mrow></msub></mrow></msup><mo stretchy='true'>)</mo></mrow></math> and a novel potential <math altimg='si3.svg'><mi>V</mi><mo stretchy='false'>(</mo><mi>&#981;</mi><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mi>&#955;</mi><msubsup><mrow><mi>M</mi></mrow><mrow><mi>p</mi><mi>l</mi></mrow><mrow><mn>4</mn><mo linebreak='badbreak' linebreakstyle='after'>&#8722;</mo><mn>2</mn><mi>&#945;</mi></mrow></msubsup><msup><mrow><mi>&#981;</mi></mrow><mrow><mn>2</mn><mi>&#945;</mi></mrow></msup><msup><mrow><mi mathvariant='normal'>sin</mi></mrow><mrow><mn>2</mn></mrow></msup><mo>&#8289;</mo><mrow><mo stretchy='true'>(</mo><mfrac><mrow><mi>&#946;</mi><msubsup><mrow><mi>M</mi></mrow><mrow><mi>p</mi><mi>l</mi></mrow><mrow><mi>&#945;</mi></mrow></msubsup></mrow><mrow><msup><mrow><mi>&#981;</mi></mrow><mrow><mi>&#945;</mi></mrow></msup></mrow></mfrac><mo stretchy='true'>)</mo></mrow></math>. With the help of COBE normalization, we constrain values of different parameters and extract the field value at the time of Hubble crossing. The end of inflation is marked by <math altimg='si4.svg'><msub><mrow><mover accent='true'><mrow><mi>&#1013;</mi></mrow><mrow><mo stretchy='false'>&#732;</mo></mrow></mover></mrow><mrow><mi>v</mi></mrow></msub><mo stretchy='false'>(</mo><msub><mrow><mi>&#981;</mi></mrow><mrow><mi>i</mi></mrow></msub><mo stretchy='false'>)</mo><mo linebreak='goodbreak' linebreakstyle='after'>=</mo><mn>1</mn></math> where <math altimg='si5.svg'><msub><mrow><mi>&#981;</mi></mrow><mrow><mi>i</mi></mrow></msub></math> is the field value at the end of inflation. Equipped with these values, we then move on to calculate values of spectral index <math altimg='si6.svg'><msub><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msub></math> and tensor-to-scalar ratio <italic>r</italic>. Our predicted values of <math altimg='si6.svg'><msub><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msub></math> and <italic>r</italic> fall within their observed values from the Planck 2018 survey and BICEP/Keck array measurement for both potential, making them plausible candidates for the inflationary model. We also display the variation of the tensor-to-scalar ratio and spectral index with the coefficient of RT-mixing term for fixed values of e-fold number. There, we find the existence of two local maxima of <math altimg='si6.svg'><msub><mrow><mi>n</mi></mrow><mrow><mi>s</mi></mrow></msub></math>, which occur at a negative and a positive value of <italic>&#958;</italic>, the coefficient of <italic>RT</italic>-mixing term. Our analysis finds a significant impact of <italic>&#958;</italic> on values of observables.

Sohan Kumar Jha

Anisur Rahaman

Non-minimal <italic>RT</italic> coupling and its impact on inflationary evolution in <italic>f</italic>( <italic>R</italic>, <italic>T</italic>) gravity