Within the symmetric mass generation (SMG) approach to the construction of lattice chiral gauge theories, one attempts to use interactions to render mirror fermions massive without symmetry breaking, thus obtaining the desired chiral massless spectrum. If successful, the gauge field can be turned on, and thus a chiral gauge theory can be constructed in the phase in which SMG takes place. In this paper we argue that the zeros that often replace the mirror poles of fermion two-point functions in an SMG phase should be “kinematical” singularities. We conjecture that the SMG interactions generate opposite-chirality bound states, which combine with the gapped elementary mirror states to form massive Dirac fermions. The propagator zeros can then be avoided by choosing an appropriate set of interpolating fields that contains both elementary and composite fields. This allows us to apply general constraints on the existence of a chiral fermion spectrum which are valid in the presence of (nongauge) interactions of arbitrary strength, including in any SMG phase. Using a suitably constructed one-particle lattice Hamiltonian describing the fermion spectrum, we formulate a generalized no-go theorem which establishes the conditions for the applicability of the Nielsen-Ninomiya theorem to this Hamiltonian. If these conditions are satisfied, the massless fermion spectrum must be vectorlike. We add some general observations on the strong coupling limit of SMG models. We also elaborate on the qualitative differences between four-dimensional and two-dimensional theories that limit the lessons that can be drawn from two-dimensional models. Finally, we compile a list of open questions which must be addressed in any SMG model in order to determine whether or not it is subject to the generalized no-go theorem.

In this paper, we investigate the distribution amplitudes (DAs) of pseudoscalar mesons within the light-front quark model, and the $n$th Gegenbauer moment $a_n(\mu )$, $\xi$ moment $⟨{\xi }^n⟩$, and transverse moment $⟨{\mathbf{k}}_{\perp }^n⟩$ are also studied. Two parameter sets are adopted by fitting to mesonic decay constants or mass spectra, leading to distinct schemes for numerical analysis. Our results reveal several key insights: (1) Under scheme I, the second Gegenbauer moment for the pion, $a_{2,\pi }=0.054$, is in excellent agreement with predictions from the platykurtic model and the nonlocal chiral quark model. Meanwhile, scheme II yields $a_{2,\pi }=0.126$, which is consistent with lattice QCD, Dyson-Schwinger equation, and data-driven light-cone sum rules analyses. Furthermore, we observe that ${\varphi }_{2,\pi }={\varphi }_{3,\pi }^P$ with the replacement $M\to M_0$. (2) Flavor symmetry breaking effects are found to be more significant in higher-twist DAs, with a notable relation $a_1^P\approx 2a_1$ emerging in heavy meson systems. (3) Interestingly, numerical analysis indicates that the transverse moment $⟨{\mathbf{k}}_{\perp }^n⟩$ is twist independent with the replacement $M\to M_0$. Additionally, we propose an empirical scaling relation $\frac{\mathrm{\Delta }{m}^{0.61}}{{\beta }^{1.10}}{x}_p=0.67$ to effectively describe the shape of DAs for heavy mesons. Collectively, these results demonstrate that mass asymmetry remarkably influences DAs and kinds of moments; these theoretical predictions will be tested in future experiments.

In this work we study the quark-meson model within a real-time formulation of the functional renormalization group (FRG) on the Schwinger-Keldysh contour. First, we discuss in detail the symmetry of thermal equilibrium for the fermionic sector of the Keldysh action. We take into account dissipation for the bosonic degrees of freedom in the spirit of the Caldeira-Leggett model by coupling the system to an $O(4)$ invariant external heat bath. We study the effect of dissipation on static equilibrium properties, most prominently on the FRG flow of the effective potential and thus on the resulting phase diagram. We find that, unlike in classical systems, through the contributions from nonzero Matsubara modes the dissipative dynamics can in general have an effect on static observables. We investigate these effects within two phenomenological models for the temperature dependence of the pion damping to verify that they are quantitatively small. To estimate their largest possible influence, we consider limits where the damping constants approach infinity.

We introduce an array-scalable, magnon-based detector to search for the spin-dependent interactions of electron-coupled axion dark matter with mass in the $1-100\mathrm{\mu }\mathrm{eV}$ range. These axions can excite single magnons in magnetic targets, such as yttrium iron garnet (YIG) spheres, which are subsequently sensed by the detector. In our concept, this sensing is implemented by coupling the magnons in the YIG spheres to magnetic-field-resilient single-electron charge-qubits, whose state is then interrogated with a quantum nondemolition measurement. Using standard superconducting fabrication techniques, it is possible to integrate many YIG sphere-qubit sensors, forming a large detector array. We outline the detector design and operation for our concept, and determine its sensitivity to axion dark matter. We find that using available technology can already exceed the sensitivity of previous ferromagnetic haloscopes, and further improvements in performance would search for electron-coupled axion dark matter in unexplored parameter space.

We study a neutrino mass model with Froggatt-Nielsen (FN) like modular symmetry. The FN mechanism requires an additional gauge symmetry, $U(1{)}_{\mathrm{FN}}$, which is spontaneously broken at high energies. But in this work, we do not need an extra symmetry as modular weights play the role of the FN charges of the additional $U(1{)}_{\mathrm{FN}}$ symmetry. We have constructed a neutrino mass model using FN-like modular symmetry in the $T^{\prime }$ group. This model can accommodate neutrino oscillation parameters and also address other phenomena beyond the Standard Model, such as neutrinoless double beta decay and the baryon asymmetry of the Universe.

In this study, we explore various lab-frame angular observables at the Large Hadron-electron Collider (LHeC) to test their sensitivity to the most general structure of the Higgs ($H$) to neutral weak boson ($Z$) coupling ($HZZ$) via the process $e^{-}p\to e^{-}Hj$ at the center of mass energy $\sqrt{s}\approx 1.3\mathrm{TeV}$. The most general Lorentz structure of the $HZZ$ coupling beyond the standard model is composed of two $CP$-even (${\lambda }_{1Z}$ and ${\lambda }_{2Z}$) and one $CP$-odd (${\tilde{\lambda }}_Z$) component. In a previous study, we investigated the absolute value of azimuthal correlation ($|\mathrm{\Delta }\varphi |$) between the final state electron and the jet to derive constraints on the nonstandard $HZZ$ couplings. This choice of observable is motivated by its potential to discriminate between $CP$-odd and $CP$-even couplings in the $e^{-}p\to {\nu }_{e}Hj$ process. Since the process $e^{-}p\to e^{-}Hj$ has an electron in the final state, one can construct more angular observables. In addition to $|\mathrm{\Delta }\varphi |$, we identify new angular observables: the sign-sensitive azimuthal correlation ($\mathrm{\Delta }\varphi$) and the polar angle of the final state electron ($\theta$), which are suitable for constraining nonstandard $HZZ$ coupling. Our analysis shows that these new angles improve the constraints on ${\lambda }_{2Z}$ and ${\tilde{\lambda }}_Z$ in the range of 48%–67%. We also study the potential of the asymmetry in $\mathrm{\Delta }\varphi$ to constrain the parameters corresponding to the $CP$-odd coupling.

In this work, we investigate the dipion transition processes $X(3872)\to \pi \pi {\chi }_{cJ}$ ($J=0$, 1, 2) within the framework of heavy hadron chiral perturbation theory, treating $X(3872)$ as a molecular state composed of $D{\overline{D}}^{*}+\mathrm{H}.\mathrm{c}.$ components. By analyzing the box and triangle loop diagrams with the nonrelativistic effective field theory power-counting rule, we demonstrate that box diagrams dominate these dipion transition processes. Branching ratios are calculated as functions of the mixing angle $\theta$, which parametrizes the neutral and charged meson compositions of the $X(3872)$. Our results indicate that the branching fractions for $X(3872)\to \pi \pi {\chi }_{c0}$, $X(3872)\to \pi \pi {\chi }_{c1}$, and $X(3872)\to \pi \pi {\chi }_{c2}$ are of the orders of ${10}^{-4}$, ${10}^{-3}$, and ${10}^{-5}$, respectively. We also predict the ratios $\mathcal{B}[X(3872)\to \pi \pi {\chi }_{c0/2}]/\mathcal{B}[X(3872)\to \pi \pi {\chi }_{c1}]$ and $\mathcal{B}[X(3872)\to {\pi }^{+}{\pi }^{-}{\chi }_{cJ}]/\mathcal{B}[X(3872)\to {\pi }^0{\pi }^0{\chi }_{cJ}]$. The latter deviates from isospin-symmetry expectations, revealing various degrees of isospin violation. By studying the ${\pi }^{+}{\pi }^{-}$ and ${\pi }^{+}{\chi }_{cJ}$ invariant mass spectra, we find a double-bump structure in the ${\pi }^{+}{\pi }^{-}$ invariant mass distributions of the process $X(3872)\to {\pi }^{+}{\pi }^{-}{\chi }_{c1}$ and ${\pi }^{+}{\chi }_{c0}$ invariant mass distribution of the process $X(3872)\to {\pi }^{+}{\pi }^{-}{\chi }_{c0}$, which could be tested by future experimental measurements.

Recent computations in gravity suggest that nonsupersymmetric extremal black holes lack any sizeable ground state degeneracy. We confirm this for a D-brane description of nonsupersymmetric four-charge extremal black holes in $\mathrm{N}=8$ string theory. The microscopic description comprises four stacks of D-branes wrapping various cycles of the internal six torus and intersecting at a point. The orientations of the stacks are such that supersymmetry is broken completely. We construct the low energy worldline Lagrangian for the brane system, which is seen to have 32 Goldstinos and 28 Goldstones. The Hamiltonian has a unique ground state, which carries a nonzero energy implying the absence of any truly extremal state. Our arguments rely on symmetry and hence should hold in the supergravity regime as well.

The main goal of string phenomenology is to find realistic models of particle physics and cosmology within string theory. Dark bubble cosmology is an alternative to string compactifications, where our Universe lives on a bubble expanding in a higher-dimensional spacetime. This construction is inherently nonsupersymmetric and can yield a four-dimensional realistic cosmology, where radiation behaves as expected due to its coupling to higher-dimensional fields. We study the coupling of the electroweak and strong sectors to the induced braneworld gravity via the same mechanism. While the electroweak sector is unaffected, the gravitational and inertial masses of the proton differ significantly, severely violating measurements of the equivalence principle.

We study the complexity of the gravity dual to the confining $SU(N)\times SU(N+M)$ Klebanov-Strassler gauge theory, which is an important test case for holographic complexity in higher-dimensional and nonconformal gauge-gravity dualities. We emphasize the dependence of the complexity on parameters of the gauge theory, finding a common behavior with confinement scale for several complexity functionals. We also analyze how the complexity diverges with the UV cutoff, which is more complicated than in AdS backgrounds because the theory is nonconformal. Our results may provide new perspectives on questions in the holographic complexity program as well as a starting point for further studies of complexity in general gauge-gravity dualities.

The Unruh effect is notoriously difficult to detect, as it is exponentially overwhelmed by Wigner-Weisskopf spontaneous emission. We show that this fundamental obstacle can be overcome by harnessing multidetector quantum interference. By preparing a system of three entangled Unruh-DeWitt detectors in a specific W state, the spontaneous emission channels can be forced to destructively interfere and vanish, thereby “saving” the Unruh signal by coherently silencing this dominant noise. Our central result is the derivation of the condition for complete and simultaneous cancellation of all right- and left-traveling emission modes. We find this requires preparing the detectors in a unique entangled state whose real-valued coefficients are fixed by an elegant geometric constraint, given by a ratio of sines of the logarithms of the detector accelerations. This work establishes multidetector entanglement as a precision tool for noise cancellation in relativistic quantum settings, offering a new pathway toward the definitive observation of the Unruh signal.

There exist two consistent theories of massless, self-interacting gravitons, which differ by their local symmetries: general relativity and Weyl transverse gravity. We show that these two theories are also the only two metric descriptions of gravity in four spacetime dimensions which obey the equivalence principle for test gravitational physics. We further analyze how the weaker formulations of the equivalence principle are realized in Weyl transverse gravity (and its generalizations). The analysis sheds light on the behavior of matter fields in this theory.

We develop a fully numerical framework to compute and visualize the hypershadow [J. a. P. A. Novo et al., Hypershadows of higher dimensional black objects: A case study of cohomogeneity-one $\mathrm{d}=5$ Myers-Perry, J. High Energy Phys. 11 (2024) 171], the three-dimensional generalization of the black hole shadow in five-dimensional spacetimes. Our method is based on backward ray tracing and allows flexible control over observer position, enabling the reconstruction of the full shadow volume. For visualization, we combine discrete sampling with surface contouring and introduce reflection difference maps on central slices to quantify mirror symmetries. Applying this method to the Schwarzschild-Tangherlini and Myers-Perry geometries, we validate the former’s spherical symmetry and systematically discuss the hypershadow’s dependence on observer position and black hole spin parameters. We also provide compact quantitative measures for size reduction and global displacement, revealing clear monotonic trends. The framework is readily extendible to other metrics and opens the way to numerical studies of more exotic objects, such as black rings and their prospective toroidal hypershadows.

The demand for long and accurate gravitational waveforms is increasing as we prepare for the next generation of detectors and seek to improve current waveform models. However, numerical relativity waveforms, while highly accurate, are often too short for these applications due to their high computational cost. Hybrid waveforms, which stitch together gravitational wave signals from different modeling approaches, provide a way to generate complete inspiral-merger-ringdown signals. While hybridization is well established for aligned-spin systems, precession introduces additional complexities due to gauge ambiguities, frame dependence, or spin dynamics. Here we study the challenges associated with alignment of precessing waveforms and present a systematic approach for constructing hybrid waveforms of precessing quasicircular systems. Our approach relies on minimal assumptions about the merger waveforms and employs the quadrupole-aligned frame to mitigate mode mixing. Our method is designed to be robust and broadly applicable, imposing minimal constraints on the input waveforms. This framework expands the applicability of hybridization techniques, facilitating flexible hybrid construction for parameter estimation, model calibration, and gravitational-wave data analysis.

Primordial black holes (PBHs) are a compelling dark matter candidate and a unique probe of small-scale cosmological fluctuations. Their formation is usually attributed to large positive curvature perturbations, which collapse upon Hubble reentry during radiation domination. In this work we investigate instead the role of negative curvature perturbations, corresponding to the growth of primordial void (PV) like regions. Using numerical relativity simulations, we show that sufficiently deep PV can undergo a nonlinear rebounce at the center, generating an effective overdensity that eventually collapses into a PBH. We determine the critical threshold for this process for a variety of equations of state, and demonstrate that the resulting black holes masses obey a scaling relation analogous to the standard overdensity case. These results establish primordial voids as a novel channel for PBH formation and highlight their potential impact on PBH abundances and cosmological signatures.

We generalize the analytic formula for the gravitational-wave spectrum from bubble collisions during a cosmological first-order phase transition, under the thin-wall and envelope approximations, by incorporating the effect of cosmic expansion in the FLRW metric. Along with presenting the complete analytic expression and corresponding numerical results, we also derive simplified formulas valid in the large- and small-$k$ limits, as well as in the Minkowski limit. The latter expansion reveals that the Minkowski approximation breaks down for $\beta /H_{*}\lesssim 10$, where $\beta$ denotes the inverse duration of the phase transition and $H_{*}$ the Hubble parameter at its completion. Furthermore, the next-to-leading-order term contributes about a 10% correction for $\beta /H_{*}\sim 140$, a typical value for the electroweak phase transition.

We investigate the observational viability of Nash gravity as an alternative to the standard $\mathrm{\Lambda }\mathrm{CDM}$ cosmology. Based on Nash’s embedding theorem, the model introduces orthogonal perturbations via variations in the extrinsic curvature, generating scalar-type metric perturbations directly from geometry, without the need to introduce additional fields. We confront the model with current observational data, including cosmic microwave background measurements from Planck, baryon acoustic oscillations from DESI-DR2, and recent type Ia supernova compilations. Our analysis shows that Nash gravity provides a good fit to the data, yielding a slightly higher value for the Hubble constant, $H_0=69.32\pm 0.72\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$, compared with the $\mathrm{\Lambda }\mathrm{CDM}$ model, thus offering a potential alleviation of the $H_0$ tension. Furthermore, the model naturally predicts a suppressed growth of structure, with $S_8\approx 0.76$ across various joint analyses, potentially alleviating the so-called $S_8$ tension, assuming that this discrepancy is not solely due to systematic effects in other independent measurements. In some cases, Nash gravity achieves a better fit to the data than the $\mathrm{\Lambda }\mathrm{CDM}$ paradigm at the $2\sigma$ level.

The accretion of dark matter (DM) onto compact objects and the potential gravitational collapse of neutron stars due to this accretion has become a promising indirect probe of DM properties, complementing terrestrial experiments. We show that the accretion flux of DM on stellar objects is amplified in binary systems due to the complex gravitational interaction of said particles with the binary. We perform few-body Monte Carlo simulations to show that this amplification factor is $\sim 4–5$ for circular binaries, small DM velocity dispersions and mass ratios $q\gtrsim 0.3$. We use this factor to improve previous constraints on the scattering cross section of nonannihilating bosonic DM with baryonic matter, and derive upper bounds on this cross section from the observation of the binary NS merger associated with GW170817. We also show that the maximally accretable mass fraction of DM by binary NSs is $\lesssim {10}^{-3}$, even for extreme DM densities only possible in DM spikes, due to the dynamical friction exerted by the ambient DM.