The Galactic Center excess (GCE) of GeV <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math> rays may hint at dark matter (DM), yet its origin remains debated. Motivated by this, we survey weakly interacting massive particle (WIMP) models that can fit the GCE while satisfying relic-density, direct-detection (DD), and indirect-detection (ID) bounds. We group candidates into hadronic (Higgs portals; simplified scalar/vector mediators), leptonic [<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mrow><msub><mi>L</mi><mi>i</mi></msub><mo>−</mo><msub><mi>L</mi><mi>j</mi></msub></mrow></msub></math>], and mixed [<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><msub><mo stretchy="false">)</mo><mrow><mi>B</mi><mo>−</mo><mi>L</mi></mrow></msub></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math>-portal] classes. Across all cases, present DD and dwarf-spheroidal <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi></math>-ray limits exclude wide regions, leaving mainly narrow resonant funnels with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mrow><mi>DM</mi></mrow></msub><mo>≃</mo><msub><mi>m</mi><mrow><mi>med</mi></mrow></msub><mo>/</mo><mn>2</mn></math> and portal couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>≪</mo><mn>1</mn></math>. In hadronic setups, scalar and vector Higgs portals survive only in a thin strip near <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>h</mi></msub><mo>/</mo><mn>2</mn><mo>≃</mo><mn>62.5</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> with portal couplings <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo>∼</mo><msup><mn>10</mn><mrow><mo>−</mo><mn>4</mn></mrow></msup></math>, while the Dirac Higgs and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>Z</mi></math> portals are essentially excluded. The UV-complete vector Higgs portal retains resonant bands whose viable portal strength depends on the mixing angle. Simplified scalars allow small windows for complex-scalar or vector DM; Dirac DM is strongly disfavored, whereas a pseudoscalar with Dirac DM remains viable over a broader parameter range. For a simplified <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>Z</mi><mo>′</mo></msup></math> mediator, a pure vector coupling leaves only a marginal region, while pure axial is excluded by DD/ID bounds. In leptonic scenarios, inverse-Compton emission is essential: <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>e</mi></msub></math> (and, to a lesser extent, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo>−</mo><mi>L</mi></math>) fits the GCE with near-thermal cross sections, while <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>L</mi><mi>μ</mi></msub><mo>−</mo><msub><mi>L</mi><mi>τ</mi></msub></math> is disfavored. Overall, viable WIMP explanations are constrained to the finely tuned resonant regime, with leptophilic vectors and pseudoscalar portals emerging as the most robust options.

United States

Chuiyang Kong

Italy

Mattia Di Mauro

Comprehensive study of WIMP models explaining the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>F</mi><mi>e</mi><mi>r</mi><mi>m</mi><mi>i</mi></math>-LAT Galactic Center excess

We discuss a new formula for the symplectic structure on the phase space of open string field theory. Revisiting the setup of Cho, Mazel, and Yin, we use the formula to compute the energy of rolling tachyon solutions on unstable D-branes. An important aspect of the analysis is dealing with the singular ultraviolet behavior of string vertices in Lorentzian signature, a feature we refer to as $\textit{transgressive locality}$. This forces us to carry out computations in momentum space, where time and causality are somewhat obscure. Nevertheless the symplectic structure appears to be sensible, giving results in agreement with boundary state computations. As further confirmation of our methods, we study the symplectic structure for rolling tachyons in scalar effective field theory, where vertices show similar high energy behavior to string field theory but the physics is that of local field theory. This model gives interesting insight into the runaway oscillations of the rolling tachyon.

Czechia

Vinícius Bernardes

Theodore Erler

Atakan Fırat

Symplectic structure in open string field theory. Part I. Rolling tachyons

The <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>I</mi><mo>=</mo><mfrac><mn>3</mn><mn>2</mn></mfrac></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>π</mi><mi>K</mi></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>s</mi></math>-wave scattering phase shift is computed by lattice quantum chromodynamics with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>N</mi><mi>f</mi></msub><mo>=</mo><mn>3</mn></math> flavors of Asqtad-improved staggered fermions. The energy-eigenvalues of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>π</mi><mi>K</mi></math> systems at one center of mass frame and six moving frames using moving wall source technique are used to get phase shifts by Lüscher’s formula and its extensions. The calculations are good enough to acquire effective range expansion parameters: scattering length <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi></math>, effective range <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>r</mi></math>, and shape parameter <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>P</mi></math>, which are in good agreement with our explicit analytical predictions in three-flavor chiral perturbation theory at next-to-leading order. All results are fairly consistent with experimental measurements, phenomenological studies, and lattice estimations. Numerical computations are implemented at a fine (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>a</mi><mo>≈</mo><mn>0.082</mn><mtext> </mtext><mtext> </mtext><mi>fm</mi></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>L</mi><mn>3</mn></msup><mi>T</mi><mo>=</mo><mn>4</mn><msup><mn>0</mn><mn>3</mn></msup><mn>96</mn></math>) lattice ensemble with physical quark masses.

China

Ziwen Fu

Qu-Zhi Li

Jun Wang

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>I</mi><mo>=</mo><mfrac><mrow><mn>3</mn></mrow><mrow><mn>2</mn></mrow></mfrac></mrow></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>π</mi><mi>K</mi></math> <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>s</mi></math>-wave scattering length from lattice QCD

In this work, we derive a novel set of equations — the $\textit{Asymptotic Baxter-Bethe Ansatz}$ —that determine the asymptotic spectrum of Regge trajectories in the BFKL regime of $$ \mathcal{N}=4 $$ SYM. In this challenging limit, our method yields multi-loop results in the ’t Hooft coupling, with the perturbative accuracy increasing as the quantum numbers grow. Our formalism not only provides a straightforward path to obtain multi-loop perturbative data, as we demonstrate, but also enables the classification of trajectories, paving the way for systematic non-perturbative studies up to the strong-coupling regime.

United Kingdom

Sweden

Simon Ekhammar

Nikolay Gromov

Michelangelo Preti

Regge trajectories of $$ \mathcal{N}=4 $$ SYM. Part I. General Asymptotic Baxter-Bethe Ansatz

An $\textit{SU}$(3) flavor projection operator technique is implemented to construct the baryon-meson scattering amplitude within the framework of the $1/N_c$ expansion of quantum chromodynamics (QCD), where $N_c$ represents the number of color charges. The operator technique is implemented to evaluate not only the lowest-order scattering amplitude but also effects from the first-order perturbative $\textit{SU}$(3) flavor symmetry breaking and strong isospin breaking. The most general expression is obtained by explicitly accounting for the effects of the decuplet-octet baryon mass difference. At order ${\cal{O}}(1/N_c^2)$ , a large number of unknown operator coefficients appear, and therefore, there is little additional predictive power unless leading and subleading terms are retained. Although the resultant expression is sufficiently general that it can be applied to any incoming and outgoing baryons and pseudo scalar mesons, provided that the Gell-Mann--Nishijima scheme is respected, results for $N\pi\to N\pi$ scattering processes are explicitly considered.

Víctor Miguel Banda Guzmán

Rubén Flores-Mendieta

Johann Hernández

Use of $\textit{SU}$(3) flavor projection operators to construct baryon-meson scattering amplitudes in the 1/ N$_{c}$ expansion * The authors are grateful to Consejo Nacional de Humanidades, Ciencias y Tecnologías (Mexico) for support through the $\textit{Ciencia de Frontera}$ project CF-2023-I-162

We study the concept of a dark energy star, which is assumed to be composed of both dark and conventional matter in a modified teleparallel gravity. After employing a specific viable stellar model, we build the corresponding equations of motion that govern our further analysis. We then calculate the analytical form of the spherical geometric function, accompanied by an embedding class I choice, which states that the 4-dimensional geometry can be placed in a 5-dimensional planar space. With the help of a specific dark energy state equation, we model our system to investigate the role of dark energy on key stellar characteristics, such as equilibrium, star mass, and compactness, among other aspects, in the presence of torsion terms. This will lead us to investigate the stable epochs of the corresponding stellar structure through parameters such as pressure, mass function, density, and surface redshift, among others. We will then calculate the maximum allowable stellar matter quantity by utilizing the M-R diagram. It is inferred that, under certain parametric geometric zones, torsion-based correction supports a realistic and singularity-free star model. The system is seen to obey all energy conditions and stability criteria proposed by some theoretical backgrounds.

Pakistan

Z. Yousaf

U.A. Khokhar

Uzbekistan

Javlon Rayimbaev

Otaboyev Sirajiddin

Aybek Seytov

Azerbaijan

M.Z. Bhatti

Existence of class-I dark energy stellar models

In this work, we explore how the 2-Higgs doublet model (2HDM) type-I, extended by an inert doublet, can provide an explanation for the recently observed excesses at the Large Hadron Collider (LHC) in the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>γ</mi><mi>γ</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>τ</mi><mo>+</mo></msup><msup><mi>τ</mi><mo>−</mo></msup></math> final states. Hence, by imposing theoretical constraints and experimental bounds on the model parameter space, our findings show that a light <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>C</mi><mi>P</mi></math>-even Higgs boson, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>h</mi></math>, with a mass around 95 GeV, can account for these anomalies. This result aligns with the excess in <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></math> signatures reported in earlier data from the Large Electron-Positron (LEP) collider.

Morocco

Ayoub Hmissou

Stefano Moretti

Larbi Rahili

Investigating the 95 GeV Higgs boson excesses within the type-I <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mo stretchy="false">(</mo><mrow><mn>1</mn><mo>+</mo><mn>2</mn></mrow><mo stretchy="false">)</mo><mi>HDM</mi></mrow></math>

Axion inflation is a well-motivated model of cosmic inflation with a rich phenomenology. The abundant production of gauge fields during axion inflation notably sources a stochastic gravitational-wave (GW) background signal, which nourishes the hope that future GW searches might have a chance to probe the model. In this paper, we scrutinize GW production during axion inflation in the gradient expansion formalism (GEF), a powerful numerical technique that captures the nonlinear dynamics of the system in the limit of vanishing axion gradients. We focus on single-field axion inflation coupled to a pure Abelian gauge sector, i.e., pure axion inflation (PAI), and perform the first-ever detailed parameter scan of GW production in the Abelian PAI model close to the onset of strong backreaction. We approximate the axion potential around its minimum by a quadratic mass term and study the tensor modes that exit the Hubble horizon as the axion rolls down this potential. Remarkably enough, we find that GW signals within the reach of future GW interferometers can only be realized in parameter regions that also lead to strong backreaction and that are in conflict with the upper limit on ∆$\textit{N}$ , i.e., the allowed energy density of dark radiation. This observation defines a clear target for future lattice studies of axion inflation that may confirm or improve the predictions of our GEF benchmark.

Germany

Richard Eckardstein

Japan

Kai Schmitz

Ukraine

Oleksandr Sobol

Gravitational waves from axion inflation in the gradient expansion formalism. Part I. Pure axion inflation

The electroweak sphaleron is a static, unstable solution of the Standard Model classical field equations, representing the energy barrier between topologically distinct vacua. In this work, we present a comprehensive updated analysis of the sphaleron using current Standard Model parameters with the physical Higgs boson mass of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>H</mi></msub><mo>=</mo><mn>125.1</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>W</mi></msub><mo>=</mo><mn>80.4</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>, rather than the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>m</mi><mi>H</mi></msub><mo>=</mo><msub><mi>m</mi><mi>W</mi></msub></math> approximation common in earlier studies. The study includes: (i) a complete derivation of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi><mi>U</mi><mo stretchy="false">(</mo><mn>2</mn><mo stretchy="false">)</mo><mo>×</mo><mi>U</mi><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></math> electroweak Lagrangian and field equations without gauge fixing constraints, (ii) high-precision numerical solutions for the static sphaleron configuration yielding a sphaleron energy <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>E</mi><mi>sph</mi></msub><mo>≃</mo><mn>9.1</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></math>, (iii) an analysis of the minimum energy path in field space connecting the sphaleron to the vacuum (a 1D “potential barrier” as a function of Chern-Simons number), and (iv) calculation of the sphaleron single unstable mode with negative eigenvalue <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msubsup><mi>ω</mi><mo>−</mo><mn>2</mn></msubsup><mo>=</mo><mo>−</mo><mn>2.7</mn><msubsup><mi>m</mi><mi>W</mi><mn>2</mn></msubsup></math>, providing analytical fits for its eigenfunction. We find that using the measured Higgs mass modifies the unstable mode frequency, with important implications for baryon number violation rates in both early universe cosmology and potential high-energy collider signatures. These results provide essential input for accurate lattice simulations of sphaleron transitions and precision calculations of baryon number violation processes.

Konstantin T. Matchev

Sarunas Verner

Electroweak sphaleron revisited. I. Static solutions, energy barrier, and unstable modes

Extending the Standard Model (SM) with three right-handed neutrinos, the type-I seesaw model serves as the simplest and most natural scenario to successfully explain both tiny neutrino masses and the baryon number asymmetry in the Universe. In this paper, we perform a complete one-loop renormalization of the type-I seesaw model in the modified minimal-subtraction ( <math altimg='si1.svg'><mover><mrow><mrow><mi mathvariant='normal'>M</mi></mrow><mi>S</mi></mrow><mo stretchy='true'>&#8254;</mo></mover></math>) scheme. The one-loop self-energy corrections of charged leptons and Majorana neutrinos are calculated in the <math altimg='si2.svg'><msub><mi>R</mi><mi>&#958;</mi></msub></math> gauge, and the explicit expressions of all the counterterms for wave functions, fermion masses and the leptonic flavor mixing matrix are given. Furthermore, adopting the Euler-like parametrization of the 6&#8239;&#215;&#8239;6 unitary leptonic flavor mixing matrix, we derive one-loop renormalization-group equations for all the physical parameters in the <math altimg='si1.svg'><mover><mrow><mrow><mi mathvariant='normal'>M</mi></mrow><mi>S</mi></mrow><mo stretchy='true'>&#8254;</mo></mover></math> scheme, including neutrino masses, mixing angles and CP-violating phases. The modification of the one-loop renormalization of the original SM parameters due to the presence of heavy Majorana neutrinos is investigated as well. In this way, we provide a self-consistent theoretical framework to thoroughly test the type-I seesaw model at the one-loop level with future precision data.

Jihong Huang

Shun Zhou

One-loop renormalization of the type-I seesaw model in the modified minimal-subtraction scheme