The spectrum of two-dimensional adjoint QCD is surprisingly insensitive to the number of colors $N_c$ of its gauge group. It is argued that the cancellation of finite $N_c$ terms is rather natural and ultimately a consequence of the singularity structure of the theory. In short, there are no finite $N_c$ contraction terms, hence effectively there cannot be any finite $N_c$ singular terms, since the former are necessary to guarantee well-behaved principal value integrals. We evaluate and categorize the matrix elements of the theory’s light-cone Hamiltonian to show how terms emerging from finite $N_c$ contributions to the anticommutator cancel against contributions from the purely finite $N_c$ term of the Hamiltonian. The cancellation is not complete; finite terms survive and modify the spectrum, as is known from numerical work. Additionally we show that several parton-number changing finite $N_c$ matrix elements vanish independently of finiteness requirements. In particular, there is only one trace-diagonal finite $N_c$ correction. It seems therefore that considering matrix elements rather than individual contributions can provide substantial simplifications when computing the spectrum of a theory with a large symmetry group.

The Pöchl-Teller effective potential mimics an asymptotically de Sitter black hole bounded by an event horizon and a cosmological one. Owing to the benefit of being analytically soluble, the asymptotic quasinormal modes in the modified Pöschl-Teller potential have been extensively explored in the literature by various authors, and the results bear distinct features. Specifically, for small discontinuities placed at the potential’s peak, Skakala and Visser showed that the resulting modes lie primarily along the imaginary frequency axis, in line with the numerical results encountered for most black hole metrics. However, it was also suggested that under ultraviolet perturbations, asymptotic modes are expected to lie parallel to the real axis, closely intervening with recent developments on spectral instability. In this work, by numerical and semi-analytical approaches, we aim to resolve the above apparent ambiguity. The numerical scheme is based on an improved version of the matrix method, which is implemented in compactified hyperboloidal coordinates on the Chebyshev grid. It is demonstrated that both asymptotic behaviors indeed agree with the numerical findings, which is somewhat to one’s surprise. This is further complemented by a few intriguing details. Specifically, we report the emergence of a novel branch of purely imaginary modes originating from a bifurcation in the asymptotic quasinormal mode spectrum. Moreover, we demonstrate how the bifurcation and asymptotic modes evolve as the discontinuity moves away from the potential’s peak, furnishing a dynamic picture as the spectral instability unfolds. It is further argued that they can be partly attributed to the observed parity-dependent deviations occurring for the low-lying perturbed modes of the original Pöschl-Teller effective potential. Our findings are confirmed by independent numerical verifications. Besides, they are reinforced by semianalytic approaches, where one introduces a refined version of the approximation. We discuss the implications of the obtained results.

In 2023, a series of intense thunderstorm ground enhancements (TGEs) were recorded on Mount Aragats in Armenia, with seven events exceeding the fair-weather cosmic ray flux by more than 75%. This study comprehensively analyzes these TGEs, investigating the atmospheric conditions and electric fields contributing to their occurrence. Key insights include discovering relationships between TGE electron content and the location of atmospheric electric fields, recovering electron and gamma-ray energy spectra, and the impact of the cloud charge structure. The findings offer a deeper understanding of TGEs’ role in atmospheric physics and its synergy with high-energy astrophysics.

We argue that dual singlets accommodate the thermal leptogenesis in the context of metastable supersymmetry breaking. This framework suggests that the reheating temperature is as low as $\mathcal{O}({10}^4)\mathrm{GeV}$, and besides the neutrino masses, solely induced from the dual fermions, are present at $\mathcal{O}(0.1)\mathrm{eV}$. We also expect that the unstable gravitino, though long-lived, may cause a clear signal of the neutrino flux at $\mathcal{O}(10)\mathrm{MeV}$.

We consider head-on collisions at critical coupling of vortices modeled by the Abelian-Higgs model. We investigate the two-vortex scattering, whereby the vortices are excited by the shape mode causing fluctuations in the gauge-invariant quantities. When the vortices are excited with a sufficiently large amplitude the moduli space approximation fails, and we observe an interesting behavior in which the vortices can become trapped in a quasibound state with multiple bounces. We perform a detailed investigation on the behavior of these excited vortices and sample a phase space of solutions. Interestingly, we find a fractal structure dependent on the initial phase of the mode and velocity of the vortices.

We address the linear-mode analysis performed near an equilibrium configuration in the fluid rest frame with a dynamical magnetic field perturbed on a constant configuration. We develop a simple and general algorithm for an analytic solution search that works on an order-by-order basis in the derivative expansion. This method can be applied to general sets of hydrodynamic equations. Applying our method to the first-order relativistic magnetohydrodynamics, we demonstrate that the method finds a complete set of solutions. We obtain two sets of analytic solutions for the four and two coupled modes with seven dissipative transport coefficients. The former set has been missing in the literature for a long time due to the difficulties originating from coupled degrees of freedom and strong anisotropy provided by a magnetic field. The newly developed method resolves these difficulties. We also find that the small-momentum expansions of the solutions break down when the momentum direction is nearly perpendicular to an equilibrium magnetic field due to the presence of another small quantity, that is, a trigonometric function representing the anisotropy. We elaborate on the angle dependence of the solutions and provide alternative series representations that work near the right angle. This identifies the origin of a discrepancy found in recent works. Finally, we discuss the issues of causality and stability based on our analytic solutions and recent developments in the literature.

We propose a novel baryogenesis scenario where the baryon asymmetry originates directly from a hierarchy between two fundamental mass scales: the electroweak scale $v$ and the Planck scale $M_P$, in the form of $Y_B\sim \sqrt{\frac{v}{M_P}}.$ This relation straightforwardly gives the observed baryon yield today $Y_B$, which can be a hint for underlying fundamental physics. We provide an example of baryogenesis models that yield this relation. Our model is based on the neutrino-portal Affleck-Dine mechanism, which generates the asymmetry of the Affleck-Dine sector during the radiation-dominated era and subsequently transfers it to the baryon number before the electroweak phase transition. The observed baryon asymmetry is then a natural outcome of this scenario. The model is testable as it predicts the existence of a Majoron with a keV mass and an electroweak scale decay constant. The impact of the relic Majoron on the effective number of neutrinos ($\mathrm{\Delta }{N}_{\mathrm{eff}}$) can be measured through near-future cosmic microwave background observations.

Gravitational-wave interferometers have been recently proposed as a promising probe in searches for dark matter. These highly sensitive instruments are potentially able to detect the interactions of dark matter with the detector’s hardware. In this work, we explore the possibilities of discovering topological dark matter with the LIGO detectors. We analyze domain walls consisting of dark matter passing through the Earth, leaving traces in multiple detectors simultaneously. Considering dark matter interactions with light in the interferometer, and with the beam splitter, we perform the first analysis of topological dark matter with gravitational-wave strain data. We examine whether astrophysically unexpected triggers could be explained by domain-wall passages. We find that all of the binary black hole mergers we analyze favor the binary black hole merger hypothesis rather than the domain-wall hypothesis, with the closest being GW190521. Moreover, we find that some topological dark matter signals can be caught by binary black hole searches. Finally, we find that special types of glitches in the measurement data can inevitably limit the dark matter searches for certain parameters. These results are expected to guide future searches and analyses.

We show that dark matter axions or axionlike particles (ALP) induce spontaneously alternating electric currents in conductors along the external magnetic fields due to the (medium) axial anomaly, realizing the chiral magnetic effects (CME). We propose a new experiment to measure this current to detect the dark matter axions or ALP. These induced currents are the electron medium effects, directly proportional to the axion or ALP coupling to electrons, which depends on their microscopic physics. In the experimental setup, one measures the sum of the electric current due to CME and the vacuum current due to the anomalous axion-photon coupling. The CME current is, in general, subdominant by a factor of the Fermi velocity of electrons, compared to latter, unless the axion or ALP coupling to electrons is much bigger than its coupling to photons to compensate the Fermi velocity suppression. However, we find that repurposing the currently operating and planned axion haloscopes may have good sensitivity to probe the CME current.

We study the sensitivity of fixed target experiments to hadronically coupled axionlike particles (ALPs) produced in kaon decays, with a particular emphasis on current and upcoming Short-Baseline Neutrino (SBN) experiments. We demonstrate that below the kaon decay mass threshold ($m_a<m_K-m_{\pi }$) kaon decay is the dominant production mechanism for ALPs at neutrino experiments, larger by many orders of magnitude than production in pseudoscalar mixing. Such axions can be probed principally by the diphoton and dimuon final states. In the latter case, even if the axion does not couple to muons at tree level, such a coupling is induced by the renormalization group flow from the UV scale. We reinterpret prior results by CHARM and MicroBooNE through these channels and show that they constrain new areas of heavy axion parameter space. We also show projections of the sensitivity of the SBN experiment and Deep Underground Neutrino Experiment (DUNE) to axions through these channels, which reach up to a decade higher in the axion decay constant beyond existing constraints. DUNE projects to have a sensitivity competitive with other world-leading upcoming experiments.

Using the one-boson-exchange model, we investigate the interactions between the doubly charmed baryon ${\mathrm{\Xi }}_{cc}(3621)$ and the $S$ wave (anti-)kaon accounting for the $S-D$ wave mixing and coupled-channel effects. We find the coupled ${\mathrm{\Xi }}_{cc}K/{\mathrm{\Xi }}_{cc}{K}^{*}$ state with $I(J^P)=0(1/2^{-})$, the ${\mathrm{\Xi }}_{cc}{K}^{*}$ state with $0(1/2^{-})$, the ${\mathrm{\Xi }}_{cc}\overline{K}$ state with $0(1/2^{-})$, and the ${\mathrm{\Xi }}_{cc}{\overline{K}}^{*}$ states with $0(1/2^{-},3/2^{-})$ can be recommended as good doubly charmed molecular candidates with strangeness $|S|=1$. We further examine their M1 radiative decay behaviors and magnetic moments within the constituent quark model framework. This information can enhance our understanding of their inner structures, including the distribution of electric charge and the orientation of the constituent quarks’ spins.

Tracks events at the IceCube Observatory are characterized by an energetic muon crossing several kilometers before decaying. Such muons are dominantly produced in charged current (CC) muon neutrino-hadron interactions. However, muons are also produced through $W$-boson production and in the decay of tau leptons and heavy mesons created in neutral and charged current interactions induced by all neutrino flavors. In this paper, we investigate the contribution of these subleading channels to events characterized as tracks at the IceCube. Our results indicate that these channels correspond to a non-negligible fraction of the high-energy starting events track events. In addition, we show that its contributions are concentrated in muons that are less energetic than those arising from muonic neutrino CC interactions for the same visible energies of the process. Finally, we investigate the impact of these additional channels on the description of the astrophysical neutrino flux, and we find that the inclusion of these subleading processes are important in determining the parameters of the astrophysical neutrino flux.

In this paper, our focus is on exploring the gauge-invariant basis for bosonic couplings within the framework of heterotic string theories, specifically examining three-, five-, and seven-derivative terms. We thoroughly analyze the invariance of these couplings under T-duality transformations and make a notable observation: the T-duality constraint enforces the vanishing of these couplings. We speculate that this result likely holds true for all higher odd-derivative couplings as well. This is unlike the result in type I superstring theory, where, for example, the couplings of five Yang-Mills field strengths are nonzero. The vanishing of couplings is consistent with the $O(d,d+16)$ symmetry of the cosmological reduction of the effective action.

Using the harmonic superspace approach, we construct, at the linearized level, $\mathcal{N}=2$ supersymmetric curvatures generalizing scalar curvature, Ricci curvature and Weyl tensor. These supercurvatures are the building blocks of various linearized $4D,\mathcal{N}=2$ Einstein supergravity invariants. The supercurvatures involving the scalar and Ricci curvatures are analytic harmonic $\mathcal{N}=2$ superfields, while the Weyl supertensor is a chiral $\mathcal{N}=2$ superfield. As the basic distinguished feature of our construction, all these objects are expressed through the fundamental analytic gauge prepotentials $h^{++M},M=(\alpha \dot{\alpha },\alpha +,\dot{\alpha }+,5)$. The related characteristic features are the heavy use of harmonic derivatives and harmonic zero-curvature equations. On a number of instructive examples, we describe the component reduction of the superfield invariants constructed.

We construct off-shell vertex operators for the bosonic spinning particle. Using the language of homotopy algebras, we show that the full nonlinear structure of Yang-Mills theory, including its gauge transformations, is encoded in the commutator algebra of the worldline vertex operators. To do so, we deform the worldline Becchi-Rouet-Stora-Tyutin (BRST) operator by coupling it to a background gauge field and show that the coupling is consistent on a suitable truncation of the Hilbert space. On this subspace, the square of the BRST operator is proportional to the Yang-Mills field equations, which we interpret as an operator Maurer-Cartan equation for the background. This allows us to define further vertex operators in different ghost numbers, which correspond to the entire $L_{\infty }$ algebra of Yang-Mills theory. Besides providing a precise map of a fully nonlinear field theory into a worldline model, we expect these results will be valuable to investigate the kinematic algebra of Yang-Mills theory, which is central to the double copy program.

We study bounce solutions and associated negative modes in the class of piecewise linear triangular-shaped potentials that may be viewed as approximations of smooth potentials. In these simple potentials, the bounce solution and action can be obtained analytically for a general spacetime dimension $D$. The eigenequations for the fluctuations around the bounce are universal and have the form of a Schrödinger-like equation with delta-function potentials. This Schrödinger equation is solved exactly for the negative modes whose number is confirmed to be one. The latter result may justify the usefulness of such piecewise linear potentials in the study of false vacuum decay.

We investigate the combined effects of spatial curvature and topology on the properties of the vacuum state for a charged scalar field localized on rotationally symmetric 2D curved tubes. For a general spatial geometry and for quasiperiodicity condition with a general phase, the representation of the Hadamard function is provided where the topological contribution is explicitly extracted. As an important local characteristic of the vacuum state the expectation value of the current density is studied. The vacuum current is a periodic function of the magnetic flux enclosed by the tube with the period of flux quantum. The general formula is specified for constant radius and conical tubes. As another application, we consider the Hadamard function and the vacuum current density for a scalar field on the Beltrami pseudosphere. Several representations are provided for the corresponding expectation value. For small values of the proper radius of the tube, compared with the curvature radius, the effect of spatial curvature on the vacuum current is weak and the leading term in the corresponding expansion coincides with the current density on a constant radius tube. The effect of curvature is essential for proper radii of the tube larger than the radius of spatial curvature. In this limit the falloff of the current density, as a function of the proper radius, follows a power law for both massless and massive fields. This behavior is in clear contrast to the one for a constant radius tube with exponential decay for massive fields. We also compare the vacuum currents on the Beltrami pseudosphere and on locally de Sitter and anti–de Sitter 2D tubes.

The spectral amplitude of the merger-ringdown gravitational wave (GW) emitted by a comparable mass-ratio black hole merger is modeled by the greybody factor of the remnant black hole. We also include the post-Newtonian correction to the greybody factor model. Our model includes only a few fitting parameters, which could evade the overfitting issue. We perform the mass-spin inference from the simulating extreme spacetimes (SXS) data without tuning the data range of each SXS waveform. Also, we find that the exponential damping in the ringdown spectral amplitude can be modeled well with the exponential damping in the greybody factor at high frequencies. Our findings could be consistent with a conjecture that the light ring of the remnant black hole, which sources the ringdown, forms as early as during the merger stage. We discuss the formation of the light ring in the static binary solution as a first step towards the understanding of how the separation of merging black holes may affect the formation of the light ring.

Time delay interferometry (TDI) is essential for suppressing laser frequency noise and achieving the targeted sensitivity for space-borne gravitational wave (GW) missions. In paper I by Wang [Phys. Rev. D 110, 042005 (2024)], we examined the performance of the fiducial second-generation TDI Michelson configuration versus an alternative, the hybrid relay, in noise suppression and data analysis. The results showed that both TDI schemes have comparable performances in mitigating laser and clock noises. However, when analyzing chirp signal from the coalescence of massive binary black holes, the Michelson configuration becomes inferior due to its vulnerable T channel and numerous null frequencies. In contrast, the hybrid relay is more robust in dynamic unequal-arm scenarios. In this work, we further investigate the noise characterization capabilities of these two TDI configurations. Our investigations demonstrate that the hybrid relay achieves a more robust noise parameter inference than the Michelson configuration. Moreover, the performance can be enhanced by replacing the T channel of the hybrid relay with a second-generation TDI null stream $C_3^{12}$. The combined three data streams, including two science observables from the hybrid relay and $C_3^{12}$, could reduce the instabilities of noise spectra in the targeting frequency band and form an optimal dataset for characterizing noises.

In this work, we study the inverse problem of analog gravity systems which admit rotation and energy-dependent boundary conditions. By extending two recent results, we provide a recipe that allows one to relate resonant transmission spectra with effective potentials and even reconstruct the boundary condition at the core. Our methodology is based on the WKB method and the identification of universal features in the transmission. One of the main advantages of this method is that it is parameter free, and relies only on general properties of the underlying potential, instead of specific models. While the reconstruction of underlying potentials is generally not uniquely possible, the inverse method provides effective potentials with similar spectral properties to the original one. To demonstrate the accuracy and scope of our method, we apply it to a rotating imperfect draining vortex, which has been proposed as an analog system to astrophysical extreme compact objects. We conclude that the capability to explore energy-dependent boundary conditions could be of interest for experimental studies of such systems.