We discuss the predictions in the simplest theory for neutrino masses based on the spontaneous breaking of local lepton number. This theory provides a simple theoretical framework to understand the possible relation between the origin of neutrino masses and the nature of the dark matter. In this theory, one of the fields needed for anomaly cancellation is a dark matter candidate and the local lepton number is broken at the low scale. We discuss in great detail the dark matter properties showing the allowed parameter space by the relic density bounds and the predictions for direct detection. The predictions for gamma and neutrino lines from dark matter annihilation are investigated. In the case of Dirac neutrinos, the bound on the effective number of relativistic degrees of freedom plays an important role and the predictions for gamma lines could be tested in the near future. We discuss the predictions in the case of Majorana neutrinos, where the dark matter candidate has extra annihilation channels, and compare all the predictions to the case with Dirac neutrinos.

The search for heavy $W^{\prime }$ bosons in their decay modes to a lepton and a heavy neutrino offers a promising avenue for probing new physics beyond the Standard Model. This work focuses on such a signature with an energetic lepton plus a fat jet, originating from the heavy neutrino and containing a lepton. We have employed the jet substructure techniques to isolate the embedded lepton as a subjet of the fat jet. The lepton subjet fraction ($LSF$) and lepton mass drop ($LMD$) variables constructed from the lepton subjet help in separating the signal region from the background. We further study the polarization properties of the $W^{\prime }$ coupling to the lepton and heavy neutrino through the decay products of the neutrino. Instead of relying on a specific model, we employ generic couplings and explore the discrimination power. Jet substructure-based angular variables $z_{\ell }$, $z_{\theta }$, and $z_k$ are combined to form BDT scores to obtain a better separation power between the left-chiral ($V-A$) and right-chiral ($V+A$) coupling configurations. By using $C{L}_s$ type profile likelihood estimator, we could achieve $1.6\sigma -2.8\sigma$ significance of excluding one coupling configuration in favor of the other.

Minimally doubled fermion actions offer a discretization for two-flavor quantum chromodynamics without rooting, but retaining a U(1) chiral symmetry at the same time. The price to pay is a breaking of the hypercubic symmetry, which requires the inclusion and tuning of new counterterms. Similar to staggered quarks, these actions suffer from taste breaking. We perform a mixed-action numerical study with the Karsten-Wilczek formulation of minimally doubled fermions on 4stout staggered configurations, generated with physical quark masses, covering a broad range of lattice spacings. We consider a tree-level spatial Naik improvement to mitigate discretization errors. We carry out a nonperturbative tuning of the KW action with and without improvement and investigate the taste breaking and the approach to the continuum limit.

Nonperturbative effects have a small but nontrivial impact on the determination of the strong coupling from hadronic $\tau$ decay data. Several approaches have been proposed to take these into account, the two most important of which are the “truncated Operator Product Expansion (OPE)” approach and “Duality Violation (DV)-model” approach. Recently, Pich and Rodríguez-Sánchez have raised a number of criticisms of the latter approach, including, most notably, claims of the existence of (i) a supposed instability with respect to variations of the model for incorporating quark-hadron duality violations, and (ii) an alleged redundancy in the fitting strategy employed in the DV-model approach. In this paper, we investigate these criticisms and show they fail to survive more detailed scrutiny of the mathematical or numerical arguments that underpin them. We also show that, while the redundancy claim does not apply to the DV-model approach, it does, in fact, apply to the truncated OPE approach. In particular, the ${\alpha }_s$ value determined in the latter turns out to derive purely from perturbation theory, with no role played by the nonperturbative condensates determined in the rest of the analysis. This leads to the conclusion that a revision of the conventional understanding of what is learned from truncated OPE analyses is necessary and that only very limited self-consistency checks are possible within this framework. These observations raise new, nontrivial issues for the truncated OPE approach.

In the quenched electroweak theory on the lattice I construct a set of physical states which overlap the physical photon and $Z$ boson states. This is done by employing eigenstates of the covariant lattice Laplacian, in addition to the Higgs and lattice link variables, to construct gauge invariant vector boson creation operators. Diagonalizing the transfer matrix in the subspace of Hilbert space spanned by this set yields a massless photon and massive $Z$ particle, as expected. But in the numerical data there is evidence for more vector bosons in the spectrum, albeit with considerable uncertainty in their masses, with the lowest finite mass particle in the range of 3–4 GeV.

We explored the efficacy of lab-grown diamonds as potential target materials for the direct detection of sub-GeV dark matter (DM) using metallic magnetic calorimeters (MMCs). Diamond, with its excellent phononic properties and the low atomic mass of the constituent carbon, can play a crucial role in detecting low mass dark matter particles. The relatively long electron-hole pair lifetime inside the crystal may provide discrimination power between the DM-induced nuclear recoil events and the background-induced electron recoil events. Utilizing the fast response times of the MMCs and their unique geometric versatility, we deployed a novel methodology for quantifying phonon dynamics inside diamond crystals. We demonstrated that lab-grown diamond crystals fabricated via the chemical vapor deposition (CVD) technique can satisfy the stringent quality requirements for sub-GeV dark matter searches. The high-quality polycrystalline CVD diamond showed a superior athermal phonon collection efficiency compared to that of the reference sapphire crystal, and achieved energy resolution 62.7 eV at the 8.05 keV copper fluorescence line. With this energy resolution, we explored the low-energy range below 100 eV and confirmed the existence of so-called low-energy excess (LEE) reported by multiple cryogenic experiments.

We present the arguments that the X(1750) has the isospin $I=0$, and as such, it belongs to the $\varphi$ family. We base our argument on the X(1750) appearing in the $e^{+}{e}^{-}\to {\mathrm{K}}^{+}{\mathrm{K}}^{-}$ process as a narrow resonance and not appearing in the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}$ process at all.

We investigate higher-order corrections to correlators in a general CFT (conformal field theory) with the double-trace $T\overline{T}$ deformation. Standard perturbation theory proves inadequate for this problem due to the intricate stress-tensor flow induced by the deformation. To tackle this challenge, we introduce a novel technique termed the conservation equation method. This method leverages the stress tensor’s trace relation and conservation property to establish relationships between higher and lower-order corrections, and subsequently determine the correlators by enforcing symmetry properties. As an illustration, we compute first- and higher-order corrections to various types of correlators. Our results align with existing calculations in the literature and demonstrate the viability of our method for general CFTs.

We investigate the trans-series structure of a quantum mechanical system originating from a Lie-algebraic Kähler sigma model with multiple right-handed chiral fermions, extending previous results for the standard one-dimensional complex projective (${\mathbb{CP}}^1$) model [T. Fujimori et al., Nonperturbative contributions from complexified solutions in $\mathbb{C}{P}^{N-1}$ models, Phys. Rev. D 94, 105002 (2016); T. Fujimori et al.Exact resurgent trans-series and multibion contributions to all orders, Phys. Rev. D 95, 105001 (2017)] to its deformed counterpart. We identify and analyze saddle-point solutions and examine their contributions within the perturbative expansions of the ground-state energy, revealing that the ambiguity structure observed in the ${\mathbb{CP}}^1$ model persists in the deformed model as well. Additionally, we explore the role of the elongation parameter and its potential impact on higher-loop corrections and propose that it becomes relevant in shaping the system’s quantum behavior from the three-loop level. This verifies that the trans-series framework provides a comprehensive approach to capturing the structure of quantum fluctuations and ambiguities in these deformed sigma models.

We determine the energy stored in the crystal defects induced by $\mathcal{O}(10–100)\mathrm{eV}$ nuclear recoils in low-threshold ${\mathrm{CaWO}}_4$ cryogenic detectors. A machine learning interatomic potential is developed to perform molecular dynamics simulations. We show that the energy spectra expected from dark matter and neutrino coherent scattering are affected by the crystal defects and we provide reference predictions. We discuss the special case of the spectrum of nuclear recoils induced by neutron capture, which could offer a unique sensitivity to the calculated stored energies.

In quantum field theory applied to black hole spacetimes, substantial evidence suggests that the Unruh and Hartle-Hawking vacuum states become singular at Cauchy horizons. This raises essential questions regarding the impact of quantum field backreaction on the stability of Cauchy horizons in static scenarios and inner horizons in evolving spacetimes. To approach this problem, we employ analytic approximations to the renormalized stress-energy tensor (RSET) of quantum fields in four dimensions. Specifically, we utilize the anomaly-induced effective action, which generates four-dimensional approximate RSETs through a pair of auxiliary scalar fields that satisfy higher-order equations of motion. The boundary conditions imposed on these auxiliary fields yield RSETs with leading-order terms that mimic the behavior of different vacuum states. This study presents the first application of the anomaly-induced effective action method to Reissner-Nordström black hole interiors, evaluating its accuracy, applicability, and connections with prior RSET approximations. Among the range of possible states accessible through this method, we found none that remain regular at both the event and Cauchy horizons, aligning with theoretical expectations. The method shows strong agreement with exact four-dimensional RSET results for the Hartle-Hawking state but does not fully capture the unique characteristics of the Unruh state in Reissner-Nordström spacetimes. We conclude by suggesting possible extensions to address these limitations.

Recently obtained black hole solutions within the framework of beyond-Horndeski theories, which have the advantage of featuring primary hair, are generalized in the presence of two axionic fields. In order to induce a momentum dissipation, the axionic field solutions are homogeneously distributed along the horizon coordinates of the planar base manifold. We show that, despite the explicit dependence of the scalar field and the metric on the primary hair, this latter does not directly affect the calculation of transport properties. Its influence is indirect, modifying the horizon location, but the transport properties themselves do not explicitly depend on the hair parameter. We take a step further and show that even within a more general class of beyond-Horndeski theories, where the scalar field depends linearly on the hair parameter, the scalar hair still has no direct impact on the DC conductivity. This result underscores the robustness of our earlier findings, and seem to confirm that the transport properties remain unaffected by the explicit presence of the hair parameter.

Inspired by the success of system-plus-reservoir models in the theory of open systems, we investigate the dynamics of spacetime as an open system. As a preliminary step toward a comprehensive gravitation-plus-reservoir framework, we present a Schwarzschild-plus-reservoir toy model, where the influence of unknown or inaccessible degrees of freedom is captured through an interacting reservoir. The potential of this approach is illustrated by modeling quasistatic accretion processes.

We consider a general dynamical, spherically symmetric background in the cubic subclass of Horndeski theory and obtain the quadratic action for the perturbations. We analyze the stability conditions for high-energy modes and study the issue of the no-go theorem. We formulate the no-go theorem for weak dependence on one variable (time or radial) and derive its generalization to the cases which could be reduced by coordinate transformation to scenarios where the scalar field has weak dependence on one of the coordinates. Moreover, we show that a wide class of singular solutions is also prohibited within the cubic subclass of Horndeski theory.

Superradiance clouds of kinetically mixed dark photons around spinning black holes can produce observable multimessenger electromagnetic and gravitational wave signals. The cloud generates electric fields of up to a teravolt-per-meter, which leads to a cascade production of charged particles, yielding a turbulent quasiequilibrium plasma around the black hole, and resulting in electromagnetic fluxes ranging from supernova to pulsar-like luminosities. For stellar mass black holes, such systems resemble millisecond pulsars and are expected to emit pulsating radio waves and continuous gravitational waves (CWs) within the LIGO-Virgo-KAGRA (LVK) sensitivity band. We select 44 sources with approximately coincident frequencies or positive frequency drifts from existing pulsar catalogs as potential candidates of long-lasting superradiance clouds around old Galactic black holes. For a subset of 34 sources that are well measured and have not been previously targeted, we perform the first search for CW emission in LVK data from the third observing run. We find no evidence of a CW signal and place 95% confidence level upper limits on the emitted strain amplitude. We interpret these results, together with limits from previous searches, in terms of the underlying dark photon theory by performing an analysis of the expected signals from superradiance clouds from Galactic black holes. We find that, even for moderately spinning black holes, the absence of an observed CW signal disfavors a discrete set of dark photon masses between about ${10}^{-13}$ and ${10}^{-12}\mathrm{eV}/{\mathrm{c}}^2$ and kinetic mixing couplings in the range of ${10}^{-9}–{10}^{-7}$, subject to assumptions about the properties of the black hole population and the cloud’s electromagnetic emission.

A relativistic theory including two types of gravitation, tensor and scalar field, has recently been published by Zhang, providing the origin of the Hubble tension as well as that of the cosmological constant. It is shown here that the combination of scalar and tensor fields enables the relativistic theory to be compatible with Mach’s principle (MP). The scalar field can also act as an inflation field at the cosmic inflationary era and convert to dark matter particles during its oscillating era. As the quanta of the excitation states of the scalar field, unlike ordinary matter, this type of dark matter does not couple to the equilibrium state of the scalar field. The masses of the quanta are estimated to be less than 31 meV if we assume that all dark matter is of this type. The most probable mass is 2 meV. Due to the dynamic equilibrium state of the scalar field acting as dark energy, a simulated equation of state is introduced for this dynamical dark energy. Consequently, if the true space of the Universe is closed, observers who are based on the assumption of flat space would discover that the equation of state for dark energy has ever crossed $-1$ in the near past. Since Dark Energy Spectroscopic Instrument Data (DESI) imply that the equation of state may cross $-1$, then the spatial curvature of our Universe may be positive based on the gravitational scheme. These effects above are analyzed in the frame of general relativity (GR) by canonically subsuming the canonical scalar field into GR. It is also demonstrated that the new interaction between the scalar field and ordinary matter can be independently analyzed in the frame of special relativity (SR). The equations of motion of several given matter fields in the presence of the scalar gravitational field are obtained in SR frame. Unlike the GR effect of the self-interaction potential of the scalar field accelerating the expansion rate of the Universe, the so-called scalar-field-mediating force is caused by the gradient of the scalar field and is entirely an effect of SR, independent of GR. We refer to this new interaction as scalar gravitation to distinguish it from Einstein’s tensor gravitation. Since all ordinary matter couples to the scalar field in the same conformal way, the scalar field can result in forces not only between fermions but also bosons. Due to the spontaneous-symmetry-breaking of the coupling, the matter-density-dependent forces are often short ranged. In the current density of the Universe, the range of interaction is estimated to be 2.2 μm if all dark matter is attributed to the excitation of the scalar field. When the Lorentz invariant effective nonrelativistic energy density ${\rho }_{\mathrm{N}}=\rho -3P$ of the ordinary matter fluid decreases (which does not necessarily mean that the energy density $\rho$ of the fluid must be low because the fluid pressure $P$ can be high enough to make ${\rho }_{\mathrm{N}}=0$), the range of interaction will increase as a function of $1/\sqrt{{\rho }_{\mathrm{N}}}$. Thus, the scalar-mediated force will play a crucial role in the formation of galaxies, especially under relativistic conditions and extremely low energy densities of ordinary matter.

We present goku, a suite of cosmological $N$-body simulations, and the corresponding 10-dimensional emulator, gokuemu, for the nonlinear matter power spectrum. The simulations span the base parameters of $\mathrm{\Lambda }$ Cold Dark Matter ($\mathrm{\Lambda }\mathrm{CDM}$) cosmology and its extensions, including dynamical dark energy ($w_0$, $w_a$), the sum of the neutrino masses ($\sum m_{\nu }$), the effective number of neutrinos ($N_{\mathrm{eff}}$), and the running of the scalar spectral index (${\alpha }_{\mathrm{s}}$), enabling tests of new physics with data from upcoming surveys like the Roman Space Telescope, Euclid, and LSST. Designed within the mf-box framework, which integrates multiscale and multifidelity simulations, the suite includes high-fidelity simulations evolving ${3000}^3$ particles in $1(\mathrm{Gpc}/h{)}^3$ volumes and low-fidelity simulations with ${750}^3$ particles across varying box sizes. This approach achieves percent-level accuracy in high-likelihood regions and 5% accuracy across broader parameter ranges, while reducing computational costs by 94% compared to single-fidelity methods. The simulations adopt an accurate treatment of massive neutrinos, enhancing predictions of the matter power spectrum on nonlinear scales. Key innovations include an adaptive sampling strategy and the use of beam search to optimize generalization accuracy. The emulator is valid for redshifts $z\le 3$ and scales $0.01\lesssim k/(h{\mathrm{Mpc}}^{-1})\lesssim 10$. Beyond the matter power spectrum, the simulations also support analyses of other statistical measures, such as the halo mass function. The emulator and its training data are publicly available, providing a valuable resource for cosmological parameter inference and model testing.

We perform cosmological parameters estimation on Planck cosmic microwave background (CMB) maps masking the recently discovered foreground related to nearby spiral galaxies. In addition, we also analyze the association between these foreground regions and recent claims of cosmological causal horizons in localized CMB parameter estimates. Our analysis shows consistent cosmological parameter values regardless of the masking approach, though reduced sky areas introduce larger uncertainties. By modeling the new extragalactic foreground, we identify a resemblance with local parameter variation maps with a statistical significance at the $3\sigma$ level, suggesting that a simplified foreground model partially accounts, $(40–50)\%$ correlation with 15% uncertainty, for the observed causal horizons. These findings add new evidence to the existence of the new foreground associated with large spiral galaxies and show that estimates of cosmological parameters on smaller patches on the sky can be largely affected by these foregrounds, but that the parameters taken over the full sky are unaltered.

One well-known method of generating a large blue spectral index for axionic isocurvature perturbations is through a flat direction not having a quartic potential term for the radial partner of the axion field. In this work, we show how one can obtain a large blue spectral index even with a quartic potential term associated with the Peccei-Quinn symmetry breaking radial partner. We use the fact that a large radial direction with a quartic term can naturally induce a conformal limit which generates an isocurvature spectral index of 3. We point out that this conformal representation is intrinsically different from both the ordinary equilibrium axion scenario or massless fields in Minkowski spacetime. Another way to view this limit is as a scenario where the angular momentum of the initial conditions slows down the radial field or as a superfluid limit. Quantization of the nonstatic system in which the derivative of the radial field and the derivative of the angular field do not commute is treated with great care to compute the vacuum state. The parametric region consistent with axion dark matter and isocurvature cosmology is discussed.