Sterile neutrino is a promising dark matter (DM) candidate. However, the parameter space of this scenario has almost been ruled out by the X-ray observation results whenever the sterile neutrino is solely produced by the Dodelson–Widrow (DW) mechanism in the early Universe. In this letter, we propose an extension to the minimal sterile neutrino DM model by introducing the pseudo-Dirac sterile neutrino, which implies the existence of two nearly degenerate Majorana states $${\hat{N}}_{1,2}^{\phantom{a}}$$ , and a permutation symmetry. The heavy state $${\hat{N}}_1$$ is produced via the DW mechanism, and the light state $${\hat{N}}_2$$ , which serves as the DM, is produced from the decay of $${\hat{N}}_1$$ in the early Universe. The X-ray constraint is avoided by the permutation symmetry, which forbids the two-body decay of the DM into active neutrinos and photons. A promising signal of this scenario is the effective number of neutrino species, which will be precisely measured in future experiments, such as CMB stage IV. We further study the impact of this model on the cosmological parameters. The Markov Chain Monte Carlo analysis for the Planck + BAO + R19 data gives $$H_0=69.2_{-0.59}^{+0.58}$$ , which may relieve the Hubble tension.

China

Wei Chao

Da Huang

Siyu Jiang

Yue Wang

United States

Zhu-Yao Wang

Ren-Peng Zhou

Yu-feng Zhou

Pseudo-Dirac sterile neutrino dark matter

The isospin-selective reaction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mi>L</mi></msub><mi>p</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi mathvariant="normal">Σ</mi><mn>0</mn></msup></math> provides a clean probe for investigating <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>I</mi><mo>=</mo><mn>1</mn><mtext> </mtext><mtext> </mtext><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup></math> resonances. In this work, we perform an analysis of this reaction using an effective Lagrangian approach for the first time, incorporating the well-established <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1189</mn><mo stretchy="false">)</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>+</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1385</mn><mo stretchy="false">)</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>+</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1670</mn><mo stretchy="false">)</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math>, and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1775</mn><mo stretchy="false">)</mo><mn>5</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math> states, while also exploring contributions from other unestablished states. By fitting the available differential cross-section and recoil polarization data, adhering to partial-wave phase conventions same as the Particle Data Group, we find that besides the established resonances, contributions from <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1660</mn><mo stretchy="false">)</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>+</mo></msup></math>, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1580</mn><mo stretchy="false">)</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math>, and a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo stretchy="false">)</mo></math> improve the description. Notably, a <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup><mo stretchy="false">(</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup><mo stretchy="false">)</mo></math> resonance with mass around 1.54 GeV, consistent with <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1620</mn><mo stretchy="false">)</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math>, is found to be essential for describing the data in this channel, a stronger indication than found in previous analyses focusing on <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>π</mi><mi mathvariant="normal">Λ</mi></math> final states. While providing complementary support for <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1660</mn><mo stretchy="false">)</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>+</mo></msup></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1580</mn><mo stretchy="false">)</mo><mn>3</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math>, our results highlight the importance of the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi mathvariant="normal">Σ</mi><mo stretchy="false">(</mo><mn>1620</mn><mo stretchy="false">)</mo><mn>1</mn><mo>/</mo><msup><mn>2</mn><mo>−</mo></msup></math> region in <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mi>L</mi></msub><mi>p</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi mathvariant="normal">Σ</mi><mn>0</mn></msup></math>. Future high-precision measurements are needed to solidify these findings and further constrain the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup></math> spectrum.

Dan Guo

Jun Shi

Igor Strakovsky

Bing-Song Zou

Analysis of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi mathvariant="normal">Σ</mi><mo>*</mo></msup></math> via isospin selective reaction <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msub><mi>K</mi><mi>L</mi></msub><mi>p</mi><mo stretchy="false">→</mo><msup><mi>π</mi><mo>+</mo></msup><msup><mi mathvariant="normal">Σ</mi><mn>0</mn></msup></math>

This study investigates the consistency of heterotic supergravity, where the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi></math>-field gauge transformation becomes anomalous due to the Green-Schwarz mechanism, under <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math>-duality transformations. We establish that preserving <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math> duality necessitates an infinite tower of higher-derivative couplings proportional to <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>e</mi><mrow><mo>−</mo><mn>2</mn><mi mathvariant="normal">Φ</mi></mrow></msup></math>. For spacetimes featuring a Killing self-dual circle, these couplings remain immune to quantum corrections. Leveraging <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math> duality in heterotic or type I string theory, we then identify the corresponding couplings in type I theory. Notably, our analysis reveals that standard <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math>-duality transformations do not involve higher-derivative corrections. Building on this insight, we derive the explicit form of the effective action for type I theory at the <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msup><mi>α</mi><mo>′</mo></msup></math> order, adhering to a scheme that omits derivatives of the dilaton.

Iran

Mohammad R. Garousi

<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>S</mi></math> duality in higher-derivative corrections of heterotic supergravity

We extend previous holographic studies of the chiral magnetic effect (CME) by incorporating a time-dependent magnetic field. Various magnetic field profiles proposed in the literature are implemented, and their impact on the CME signal is analyzed in both static and expanding backgrounds. Interestingly, the integrated chiral magnetic current can exhibit a nonmonotonic dependence on the collision energy. Our results suggest that the CME signal is enhanced at collision energies below <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><msqrt><mi>s</mi></msqrt><mo>=</mo><mn>200</mn><mtext> </mtext><mtext> </mtext><mi>GeV</mi></math>. In addition, we derive a quasiequilibrium formula for the chiral magnetic effect in the expanding background that is valid at late times.

Sebastian Grieninger

Romania

Sergio Morales-Tejera

Spain

Pau G. Romeu

Chiral magnetic effect enhancement at lower collision energies

Using a general (nonlinear) effective field theory description of the Standard Model electroweak symmetry breaking, we analyze the impact on the electroweak oblique parameters of hypothetical heavy resonance states strongly coupled to the SM particles. We present a next-to-leading order calculation of <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mrow><mi>S</mi></mrow></math> and <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math> that updates and generalizes our previous results, including P-odd operators in the Lagrangian, fermionic cuts and the current experimental bounds. We demonstrate that in any strongly coupled underlying theory where the two Weinberg sum rules are satisfied, as happens in asymptotically free gauge theories, the masses of the heavy vector and axial-vector states must be heavier than 10 TeV. Lighter resonances with masses around 2–3 TeV are only possible in theoretical scenarios where the second Weinberg sum rule is not fulfilled.

Antonio Pich

Ignasi Rosell

Juan José Sanz-Cillero

Oblique parameters at next-to-leading order within electroweak strongly-coupled scenarios: Constraining heavy resonances

Using the Kadanoff-Baym formalism, we perform a detailed study of neutrino-antineutrino synchrotron emission from strongly magnetized, dense quark matter under conditions relevant to compact stars. Starting from an exact expression for the emission rate that fully accounts for Landau-level quantization of quarks, we derive an approximate formula applicable in the regime where quark chemical potentials are much larger than all other relevant energy scales. We demonstrate that the emission rate is largely controlled by a single dimensionless ratio between two low-energy scales: the Landau-level spacing at the Fermi surface, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>e</mi><mi>f</mi></msub><mi>B</mi><mo stretchy="false">|</mo><mo>/</mo><msub><mi>μ</mi><mi>f</mi></msub></math>, and the temperature of the quark matter, <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>T</mi></math>. When the ratio <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mo stretchy="false">|</mo><msub><mi>e</mi><mi>f</mi></msub><mi>B</mi><mo stretchy="false">|</mo><mo>/</mo><mo stretchy="false">(</mo><msub><mi>μ</mi><mi>f</mi></msub><mi>T</mi><mo stretchy="false">)</mo></math> approaches zero, many closely spaced Landau levels contribute to the emission, but the total rate vanishes as <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><mi>B</mi><mo stretchy="false">→</mo><mn>0</mn></math>. In the opposite limit, where the ratio is large, the rate is dominated by transitions between adjacent levels and is exponentially suppressed due to Landau-level quantization, which limits the thermal activation of quarks near the Fermi surface. Our results show that, even in the presence of the strongest magnetic fields expected in compact stars, the synchrotron emission remains suppressed by more than 3 orders of magnitude compared to the direct Urca process. This implies that such emission is unlikely to play any substantial role in the cooling of magnetized quark stars, at least those made of unpaired quark matter phases.

Ritesh Ghosh

Igor A. Shovkovy

Neutrino-antineutrino synchrotron emission from magnetized dense quark matter

We study compact kinks in a modified Christ-Lee model where the potential is a non-analytic function at the minima. The model has two control parameters that determine the order of the potential and its overall shape. We consider cases in which the potential has a double well shape, a triple well shape, as well as cases with a false vacuum. Compact kink solutions and their internal modes are found for each of these cases. We also study the collision of such kinks and their dependence on the solitons velocity and on the potential parameters. Several interesting dynamical processes are reported, such as the formation of central oscillons for some high velocity collisions, absence of outgoing solitons in cases where the potential is given by piece-wise linear functions, and the decoupling of subkinks from the larger kink in cases with false vacuum, leading to the formation of false vacuum bubbles.

Brazil

F. Hahne

R. Thibes

Compact kinks in a modified Christ-Lee model

We define and solve the U(1) Chern-Simons-Maxwell theory on spacetime lattice, with an emphasis on the chirality of the theory. Realizing Chern-Simons theory on lattice has been a problem of interest for decades, and over the years it has gradually become clear that there are two key points: 1) Some non-topological term, such as a Maxwell term, is necessary — this is true even in the continuum, but more manifestly on the lattice; 2) the U(1) gauge field should be implemented in the Villainized form to retain its topological properties. Putting the two ideas together seriously, we show all interesting properties of a chiral Chern-Simons theory are reproduced in an explicitly regularized manner on the lattice. These include the bosonic and fermionic level quantization, the bulk and chiral edge spectrum, the Wilson loop flux attachment (with point-split framing or geometric framing depending on the Maxwell coupling), the Wilson loop spin, the ground state degeneracy, and, most non-trivially, the chiral gravitational anomaly.

Ze-An Xu

Jing-Yuan Chen

Lattice Chern-Simons-Maxwell theory and its chirality

A technique to build perturbative series for the spectator field’s correlation functions in de Sitter space through the Fokker-Planck equation is proposed. We derive from the first-order differential equation the iterative integral relation for equal- and multi-time correlation functions. With an appropriate integration, the obtained two-point and four-point correlation functions are in agreement with quantum field theory’s ones.

Italy

Alexander Kamenshchik

Polina Petriakova

From the Fokker-Planck equation to perturbative QFT’s results in de Sitter space

The holographic complexity of a static spherically symmetric black hole, defined as the volume of an extremal surface, grows linearly with time at late times in general relativity. The growth comes from a region at a constant transverse area inside the black hole and continues forever in the classical theory. In this region the volume complexity of any spherically symmetric black hole in $\textit{d}$ + 1 spacetime dimensions reduces to a geodesic length in an effective two-dimensional JT-gravity theory. The length in JT-gravity has been argued to saturate at very late times via non-perturbative corrections obtained from a random matrix description of the gravity theory. The same argument, applied to our effective JT-gravity description of the volume complexity, leads to complexity saturation at times of exponential order in the Bekenstein-Hawking entropy of a $\textit{d}$ + 1-dimensional black hole. Along the way, we explore a simple toy model for complexity growth, based on a discretisation of Nielsen complexity geometry, that can be analytically shown to exhibit the expected late-time complexity saturation.