Some time ago it was claimed in “Spontaneous breaking of lepton number and cosmological domain wall problem” [Lazarides et al. Phys. Rev. Lett. 122, 151301 (2019)] that nonperturbative instantons of the weak interaction $\mathrm{SU}(2{)}_{\mathrm{W}}$ lead to the formation of domain walls in Majoron models owing to the anomaly of the spontaneously broken global lepton number $L$ symmetry $\mathrm{U}(1{)}_L$ with respect to $\mathrm{SU}(2{)}_{\mathrm{W}}$. We point out that it has long been known that this effect can be completely rotated away unless there is a source of explicit $B+L$ breaking present, where $B$ denotes the baryon number. We further estimate the tiny instanton-induced Majoron mass from $B+L$ breaking and analyze the cosmological impact of such domain walls. In general, this scenario does not lead to a cosmological catastrophe, and we demonstrate that the tiny instanton-induced mass can act as a bias term to collapse walls induced by a larger source of lepton number breaking. Alternatively, this electroweak Majoron could act as dynamical dark energy.

Neutron stars may exhibit pressure anisotropy arising from various physical mechanisms, such as elasticity, magnetic fields, viscosity, and superfluidity. We compute the tidal deformability and the $f$-mode oscillation frequency of anisotropic neutron stars using a phenomenological quasilocal model characterized by a single dimensionless anisotropy parameter. We find that while the relation between the tidal deformability and the $f$-mode frequency depends on the degree of anisotropy, it remains largely insensitive to variations in the equation of state (the relation between radial pressure and energy density) for a fixed anisotropy parameter, similar to the isotropic case. Leveraging this anisotropy-dependent universal relation within a statistical framework, we place constraints on the anisotropy parameter using both the gravitational-wave observation of GW170817 and simulated data for a GW170817-like event observed by a future network of detectors. We find that the anisotropy parameter can be constrained to order unity with current data, and the bounds remain comparable with future detector sensitivities. Importantly, these constraints are only weakly affected by uncertainties in the neutron-star equation of state.

We present a theoretical investigation of the radiative decay process $\mathrm{\Omega }(2012)\to \gamma \mathrm{\Omega }$, where the $\mathrm{\Omega }(2012)$ resonance with spin-parity $J^P={\frac{3}{2}}^{-}$ is treated as a dynamically generated state from $\overline{K}\mathrm{\Xi }(1530)$ and $\eta \mathrm{\Omega }$ in $s$-wave and $\overline{K}\mathrm{\Xi }$ in $d$-wave. The radiative decay width of the $\mathrm{\Omega }(2012)$ is calculated using a triangular loop mechanism, where the $\mathrm{\Omega }(2012)$ couples to the $\overline{K}\mathrm{\Xi }(1530)$ channel. Subsequently, the final-state interactions between $\mathrm{\Xi }(1530)$ and $\overline{K}$ transition to a photon and $\mathrm{\Omega }$ through the exchange of a $\mathrm{\Xi }$ baryon. Our calculations yield a radiative decay width of ${13.2}_{-5.6}^{+4.5}\mathrm{keV}$, with uncertainties arising from the model parameters. This result provides valuable insights into the nature of the $\mathrm{\Omega }(2012)$ resonance and its decay dynamics. It is expected that the calculations presented here could be verified by future experiments, which would open a new door for studying the still elusive nature of Ω(2012).

We investigate the quantum statistical properties of the confining string connecting a static fermion-antifermion pair in the massive Schwinger model. By analyzing the reduced density matrix of the subsystem located in between the fermion and antifermion, we demonstrate that as the interfermion separation approaches the string-breaking distance, the overlap between the microscopic density matrix and an effective thermal density matrix exhibits a pronounced, narrow peak, approaching unity at the onset of string breaking. This behavior reveals that the confining flux tube evolves toward a genuinely thermal state as the separation between the charges grows, even in the absence of an external heat bath. In other words, one cannot tell whether a reduced state of the subsystem arises from a surrounding heat bath or from entanglement with the rest of the system. The entanglement spectrum near the critical string-breaking distance exhibits a rapid transition from the dominance of a single state describing the confining electric string towards a strongly entangled state containing virtual fermion-antifermion pairs. Our findings establish a quantitative link between confinement, entanglement, and emergent thermality, and suggest that string breaking corresponds to a microscopic thermalization transition within the flux tube.

We investigate the lepton flavor violating (LFV) process $e^{+}{e}^{-}\to e^{+}{e}^{-}e\mu$ ($e=e^{-},e^{+},\mu ={\mu }^{-},{\mu }^{+}$) at future circular colliders, probing the effective $\gamma \gamma e\mu$ interaction through photon fusion. Within an effective field theory framework compatible with theoretical and experimental constraints, we identify regions in the parameter space of the effective couplings where the signal could be observed at the Circular Electron-Positron Collider at $\sqrt{s}=240\mathrm{GeV}$ and the Future Circular Collider (FCC-ee) at $\sqrt{s}=240$ and 350 GeV. Our analysis leverages distinctive kinematic distributions—particularly the transverse momentum of the scattered electron $p_T^{(e^{-}\mathrm{scattered})}$ and the central muon $p_T^{\mu }$—to achieve efficient signal-background separation. By employing a neural network classifier, we enhance the sensitivity beyond traditional cut-based methods, demonstrating the discovery potential of these facilities for LFV searches in the clean environment of $e^{+}{e}^{-}$ collisions.

In the $SO(5)\times U(1)\times SU(3)$ gauge-Higgs unification in the Randall-Sundrum (RS) warped space, neutrino oscillations and the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) matrix in the $W$ couplings originate from Majorana mass terms on the ultraviolet brane in the RS space. Tiny neutrino masses are generated by an inverse seesaw mechanism. The PMNS matrix in the normal ordering with ${\delta }_{\mathrm{CP}}=\pi$ naturally arises consistently with the NuFit-6.0 analysis of neutrino oscillation data.

In this paper we study a complete set of scalar and pseudoscalar four-quark operators, with a particular emphasis on their renormalization within a gauge-invariant renormalization scheme (GIRS). We focus on operators that do not mix with lower-dimensional operators by virtue of their transformation properties under the flavor-symmetry group. This class includes all $\mathrm{\Delta }F=2$ operators, as well as their partners that transform under the same irreducible representations of the flavor group. These encompass a substantial subset of $\mathrm{\Delta }F=1$ and $\mathrm{\Delta }F=0$ operators. The present analysis provides a detailed classification of all four-quark operators, exploring their Fierz identities, symmetry properties, and mixing patterns. Different variants of GIRS are explored, including a “democratic” version that treats all mixing operators uniformly. For selected variants, which exhibit smaller mixing effects, we present the conversion matrices from GIRS to the $\overline{\mathrm{MS}}$ scheme at next-to-leading order.

We explore the role of color superconductivity in quarkyonic matter under the conditions of color and electric neutrality at $\beta$ equilibrium and strong equilibrium, as relevant for neutron stars. By explicitly incorporating the color-superconducting pairing gap into the phenomenological model of a smooth transition from hadron to quark matter, we extend the known quarkyonic framework to include this essential aspect relevant at high densities. The momentum dependence of the pairing gap, motivated by the running of the QCD coupling and introduced similarly to chiral quark models with nonlocal interaction, is a novel element of the model that is crucial for enabling the simultaneous onset of all color-flavor quark states in the presence of color superconductivity. While asymptotically conformal behavior of the present model is ensured by construction, we demonstrate that reaching the conformal limit in agreement with the predictions of perturbative QCD is provided by the proper momentum dependence of the thickness of the hadron shell in momentum space. We employ the flexible metamodeling approach to nuclear matter, analyzing the structure of the hadron shell in momentum space and focusing on the effects of color superconductivity in quarkyonic matter. Similar to the effects induced by the onset of the quarkyonic phase, color superconductivity leads to stiffening of the equation of state of the neutron star matter. This causes a significant impact on observable properties of neutron stars, which are analyzed and compared to recent astrophysical and theoretical constraints. We argue that the developed model of color-superconducting quarkyonic matter provides a new, consistent tool for studying the scenario of smooth quark-hadron transition in neutron stars.

We investigate the first-order transport coefficients of a fluid made of quasiparticles with a temperature-dependent mass extracted from chiral models. We describe this system using an effective kinetic theory, given by the relativistic Boltzmann equation coupled to a temperature-dependent background field determined from the thermal masses. We then simplify the collision term using the relaxation time approximation and implement a Chapman-Enskog expansion to calculate all first-order transport coefficients. In particular, we compute the bulk and shear viscosities using thermal masses extracted from the linear sigma model coupled with constituent quarks and the NJL model.

We present a study of charge balance functions inside jets in proton-proton collisions at $\sqrt{s}=13.6\mathrm{TeV}$ using the pythia8 event generator. The balance function is a differential observable of opposite-charge correlations, which is calculated in the jet frame for inclusive charged hadrons and the identified $\pi$, $K$, and $p$. The results show a clear narrowing of the balancing width with increasing jet charged multiplicity, indicating that particle production becomes more localized in momentum space in high-multiplicity jets. This trend resembles features attributed to collective expansion in heavy-ion collisions. The species dependence highlights sensitivity to the redistribution of strangeness and baryon number during string fragmentation and color reconnection. The new color reconnection tune yields a little broader proton balance-function width in $\mathrm{\Delta }{\varphi }^{*}$ than CP5, hinting at enhanced baryon-production dynamics, whereas meson widths differ only mildly. These comparisons suggest that multiparton interactions and color reconnection contribute to the observed trends, potentially generating collectivelike features inside jets, especially in high multiplicity jets, via nontrivial color dynamics alongside standard fragmentation. Taken together, the results establish identified hadron balance functions in high multiplicity jets as a sensitive probe of hadronization and provide new constraints for models of small system collectivity.

Based on the world’s largest $\psi (3686)$ data sample, the BESIII Collaboration recently reported a substructure near the ${\pi }^{+}{\pi }^{-}$ mass threshold in the decay $\psi (3686)\to J/\psi {\pi }^{+}{\pi }^{-}$, challenging the established understanding of the dipion invariant mass spectrum. We propose that this substructure arises directly from dipion correlations. Using a chiral unitary approach, we successfully reproduce the observed anomaly, thereby providing strong evidence of dipion correlation in heavy quarkonium decays. This approach also allows us to predict the corresponding dipion correlation function.

We study the radiative process of three entangled quantum probes initially prepared in a tripartite W state. As a basic setup, we consider the probes to be inertial in flat spacetime and investigate how the radiative process is affected by different probe configurations. We take the quantum probes as either static or moving with uniform velocities and consider different switching scenarios. Our main observation confirms that the radiative process depends distinctively on the initial configuration in which the probes are arranged, as well as on the direction of the probe velocity. We also extend our analysis to a thermal environment, thereby simulating a more realistic background. We thoroughly discuss the effects due to different switchings, the thermal background, and probe motion on the radiative process of these tripartite entangled probes. We also comment on how the observations from this work can help prepare a setup least affected by quantum decoherence.

We construct static, spherically symmetric, charged traversable wormhole solutions to the Einstein-Maxwell equations, supported by bidirectional (ingoing and outgoing) null dust with negative energy and discuss a scenario for their dynamical formation from a black hole. Our solution contains a traversable throat, where the areal radius takes a minimum, although the spacetime is not asymptotically flat. In our formation scenario, the spacetime evolves sequentially from a black hole to Vaidya regions and finally to a wormhole, with each transition mediated by an impulsive null shell. We find that the radius of the wormhole throat is determined by the mass and charge of the initial black hole as well as those of the injected shell.

A new thermal view of scalar-tensor gravity, in which general relativity is the zero-temperature state of gravity, is applied to the subclass of $f(R)$ gravity theories and, specifically, to spatially homogeneous and isotropic universes. Within the limits of application of the new thermal formalism, results on the convergence to Einstein cosmology (or lack thereof) are first obtained for general $f(R)$ theories, and then illustrated with power-law and Starobinsky $f(R)$ gravity.

Extreme mass-ratio inspirals (EMRIs), in which a solar mass compact object is whirling around a supermassive black hole, act as precise tracers of the spacetime geometry and astrophysical environment around the supermassive black hole. These systems are highly sensitive to even the smallest deviations from the vacuum general relativity scenario. However, detecting these signals requires highly accurate waveform modeling up to the first postadiabatic order, incorporating self-force effects, system parameters, and environmental influences. In this paper, we focus on the impact of dark matter on gravitational waveforms. Cold dark matter in galactic centers can be redistributed by the gravitational pull of a supermassive black hole, forming a dense, spikelike profile. When an EMRI evolves in such an environment, the interaction between the binary and the surrounding dark matter can leave distinctive imprints on the emitted waveform, and thus offers a novel way to probe the nature and distribution of dark matter. We specifically examine how dark matter modifies the background spacetime. By treating these modifications perturbatively, we present a framework to incorporate dark matter environmental effects into gravitational waveform modeling at the first postadiabatic order.

The assumption that photons are massless is a foundational postulate of modern physics, yet it remains subject to experimental verification. Fast radio bursts (FRBs), with their cosmological distances and precisely measured dispersion, offer an excellent laboratory for testing this hypothesis. In this work, we propose an improved distribution function for the dispersion measure arising from extragalactic gas and demonstrate that it provides an excellent fit to mock data. We then apply this distribution to constrain the photon rest mass under the $\mathrm{\Lambda }$ cold dark matter (CDM), $w\mathrm{CDM}$, and $w_0{w}_a\mathrm{CDM}$ cosmological models, the last of which is favored by recent Dark Energy Spectroscopic Instrument baryon acoustic oscillation observations. The corresponding $1\sigma$ upper limits on the photon mass are found to be $4.83\times {10}^{-51}\mathrm{kg}$, $4.71\times {10}^{-51}\mathrm{kg}$, and $4.86\times {10}^{-51}\mathrm{kg}$, respectively, which are the most stringent constraints derived from FRBs to date. These results demonstrate that FRBs provide robust and reliable constraints, and offer strong empirical support for the massless nature of the photon.

Recently, the KM3NeT collaboration detected an astrophysical neutrino event, KM3-230213A, with an energy of approximately 220 PeV, providing unprecedented insights into the ultra-high-energy Universe. In this study, we introduce a novel likelihood framework designed to leverage this event to constrain the properties of superheavy dark matter (SHDM) decay. Our approach systematically integrates multimessenger constraints from galactic and extragalactic neutrino flux measurements by IceCube, the absence of comparable neutrino events at IceCube and Auger observatories, and the latest gamma-ray experiment upper limits. Our findings impose the most stringent constraints to date, placing a lower bound on the SHDM lifetime at $\gtrsim 5\times {10}^{29}–{10}^{30}\mathrm{s}$. Importantly, we identify, for the first time, the significant potential of galactic neutrino flux measurements in advancing dark matter research. Future investigations targeting astrophysical neutrinos originating from the Galactic Center at energies above 10 PeV will be crucial, not only for understanding the origin of the cosmic-ray knee but also for exploring the possible contributions of superheavy dark matter to our Universe.

We present a comprehensive Monte Carlo simulation of muon-induced backgrounds for the Colorado Underground Research Institute, a shallow-underground facility with $\approx 415\mathrm{meter\; water\; equivalent}$ overburden. Using coupled mute and geant4 frameworks, we characterize the production and transport of muon-induced secondaries through site-specific rock compositions and geometries, establishing a proof of concept for high-precision, end-to-end simulations. Our simulations employ angular-dependent muon energy distributions, which improve secondary flux accuracy. For the Subatomic Particle Hideout and Cryolab I research spaces, we predict total muon-induced neutron fluxes of $(8.52\pm 1.30_{\mathrm{sys}})\times {10}^{-3}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ and $(8.86\pm 1.62_{\mathrm{sys}})\times {10}^{-3}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$, respectively. Electromagnetic backgrounds are expected to dominate the total flux, with $\gamma$-ray components of $(5.54\pm 0.70_{\mathrm{sys}})\times {10}^{-1}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ and $(6.51\pm 1.06_{\mathrm{sys}})\times {10}^{-1}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$ for the Subatomic Particle Hideout and Cryolab I facilities, respectively. Additionally, we develop a depth-intensity relation to predict the muon-induced neutron flux as a function of facility depth, which is consistent with measurements across a broad range of underground depths. These results provide quantitative background predictions for experimental design and sensitivity projections at shallow- and deep-underground facilities. They further demonstrate that local geology and overburden geometry influence muon-induced secondary yields and energy spectra, emphasizing the need for site-specific simulations for accurate underground background characterization. Therefore, the simulation framework has been made publicly available for the broader low-background physics community to enable meaningful interfacility comparisons.

The Fourier transform of two-point momentum-space Feynman integrals with massless propagators and two off-shell legs can be used to prove identities between their periods, exemplified by the glue-and-cut identity. We generalize this framework to massless momentum-space Feynman integrals with three off-shell legs and obtain a similar family of identities that can be used to calculate these integrals, especially for a nonplanar subset of them, which naturally arise in the off-shell Sudakov form factors.

We investigate the anomalous chromomagnetic dipole moment (CMDM) ${\widehat{\mu }}_t^{\mathrm{BLHM}}$ of the top quark within the bestest little Higgs model (BLHM). Our study incorporates novel interactions arising from the extended Cabibbo-Kobayashi-Maskawa matrix in the BLHM and explores a broad region of the experimentally allowed parameter space, yielding CMDM values on the order of ${10}^{-3}$. This result represents an improvement over previous CMDM calculations within the BLHM and makes it competitive with other beyond the Standard Model scenarios. Experimental and model parameter uncertainties are considered and propagated through our calculations, using a Monte Carlo method.