We examine thermal warm dark matter (WDM) models that are being probed by current constraints, and the relationship between the particle dark matter spin and commensurate thermal history. We find significant corrections to the linear matter power spectrum for given thermal WDM particle masses. Two primary classes are examined: spin-$1/2$ particles (e.g., thermalized sterile neutrinos, axinos) and thermal spin-$3/2$ particles (e.g., gravitinos or nonsupersymmetric particles). We present new transfer function fits for thermal WDM candidates in particle mass regimes beyond the range of previous work, and at the scales of current and upcoming constraints. Importantly, we find that the standard, predominantly used, spin-$1/2$, thermal WDM particle produces a colder transfer function than that determined in previous work. We also analyze the entropy requirements for these WDM models to successfully produce observed dark matter densities. We explore the early Universe physics of gravitinos as either partially thermalized or fully thermalized species, which considerably changes the particle dark matter candidates’ thermalization history and effects on structure formation. For the first time, we also calculate the transfer function for thermal spin-$3/2$ WDM.

Identifying the Milky Way’s very high energy hadronic cosmic-ray accelerators—the PeVatrons—is a critical problem. While gamma-ray observations reveal promising candidate sources, neutrino detection is needed for certainty, and this has not yet been successful. Why not? There are several possibilities, as we delineated in a recent paper [T. Sudoh and J. F. Beacom, Phys. Rev. D 107, 043002 (2023)]. Here we further explore the possibility that the challenges arise because PeVatrons have a large angular extent, either due to cosmic-ray propagation effects or due to clusters of sources. We show that while extended neutrino sources could be missed in the commonly used muon-track channel, they could be discovered in the all-flavor shower channel, which has a lower atmospheric-neutrino background flux per solid angle. Intrinsically, showers are quite directional and would appear so in water-based detectors like the future KM3NeT, even though they are presently badly smeared by light scattering in ice-based detectors like IceCube. Our results motivate new shower-based searches as part of the comprehensive approach to identifying the Milky Way’s hadronic PeVatrons.

Boson stars are, at present, hypothetical compact stellar objects whose existence, however, could resolve several enigmas of current astrophysics. If they exist, either as independent astrophysical entities or as a matter admixture of more standard compact stars, then their imprints can probably be observed in the not-too-distant future from the gravitational signal of coalescing binaries in current and future GW detectors. Here we show that the multipole moments of rotating boson stars obey certain universal relations, valid for a broad set of models and various states in terms of the harmonic indices. These universal relations are equivalent to a kind of no-hair theorem for this exotic matter, allowing to map these universal (i.e., model independent) multipoles to an equally universal gravitational field around the stellar object. Further, the multipole moments can be related to observable astrophysical quantities.

Relativistic hydrodynamics is surprisingly predictive, even for systems that violate the fundamental assumptions of small gradients and small deviations from local thermal equilibrium. The method of moments can be used to extract second-order viscous hydrodynamics from a kinetic background, without the explicit request of small gradients and local equilibrium. The relativistic Boltzmann equation itself, however, is not general enough to justify hydrodynamics in all cases of interest. A possible explanation, often invoked but not yet formalized, focuses on the similarities between the relativistic Boltzmann equation and its quantum precursor, the evolution of the Wigner distribution. Indeed, it is possible to recover a systematically improvable hydrodynamic expansion. It is necessary, however, to work with a set of regularized, parametric moments. Their integrals reduce, in the classical limit, to the momentum integrals appearing in the moments expansion; most of the integrals appearing in the classical method of moments being undefined off shell. The regularized moments are, on the other hand, always well defined. Just like its classical counterpart, the evolution of the Wigner distribution can be solved exactly for a ($1+1$)-dimensional expansion with the relaxation time approximation. The convergence of the regularized expansion is checked numerically against the exact solutions. Second-order viscous hydrodynamics can be predictive even far from the kinetic limit, and far from local equilibrium.

The idea that the gravity-induced breaking of global symmetries is encoded in Planck-suppressed operators is not scale invariant: heavy particles which have nothing to do with the UV completion of gravity can mediate the breaking and produce low-energy operators (partly) suppressed by their own mass scales. Such contributions from heavy fields are typically subdominant with respect to the least Planck-suppressed operators, unless the latter are forbidden, as is usual in solutions to the axion quality problem based on four-dimensional gauge symmetries. Therefore, with a focus on axion physics, I investigate such situations and present toy examples where a nonminimal sector of heavy fields coupling to the axion generates operators whose coefficients are orders of magnitude larger than the naive Planck-suppressed estimates, despite gravity being the only source of breaking. I also stress that the key features of these toy models, namely several families of heavy fields with family-dependent gauge charges, are already present in some nonminimal QCD axion models, using the axiflavon/flaxion and the lighter-than-usual KSVZ axion as examples. This suggests that gauge-symmetry-based solutions to the axion quality problem, or of any quality problem really, need to describe complete UV scenarios or make precise UV assumptions.

The combination of precise determinations of $V_{us}$ and $V_{ud}$ hints toward a violation of the Cabibbo-Kobayashi-Maskawa matrix first row unitarity at about $3\sigma$ level. Conversely, the recent measurement of the $W$-boson mass by the CDF Collaboration exhibits significant tension with the Standard Model prediction, intensifying the conflict that may arise in models addressing the unitarity violation. We demonstrate that one vectorlike $SU(2{)}_L$ doublet with mass of a few TeV mixing with light quarks and the top quark can simultaneously account for the two anomalies, without conflicting with flavor-changing phenomena and electroweak observables. Moreover, another tension in the value of the Cabibbo angle is also reported at the $3\sigma$ level, between two determinations of $V_{us}$ obtained from semileptonic $K\ell 3$ and leptonic $K\mu 2$ kaon decays. We show that the vectorlike doublet can be at the origin of this discrepancy and the substantial positive shift in the $W$-boson mass. This unique feature of the vectorlike quark doublet may render it a crucial puzzle piece in new physics scenarios addressing the Cabibbo-Kobayashi-Maskawa matrix unitarity problem. The model can be potentially probed in future colliders.

Dark Matter (DM) residing in a secluded sector with suppressed portal interaction could evade direct detections and collider searches. The indirect detections provide the most robust probe to this scenario. Depending on the structure of the dark sector, novel DM annihilation spectra are possible. The dark shower is a common phenomenon for particles in the dark sector which take part in strong interactions and are boosted. In terms of simplified two-component DM models with vector portal interaction and pseudoscalar portal interaction, we study the dark showering effects for DM indirect detection. In those models, the heavier DM component which dominates the relic density annihilates into boosted lighter species. Together with the large coupling through which the lighter DM annihilates away in the early Universe, the showered spectra provide as the smoking gun for the DM existence. Considering bounds obtained by the AMS-02 positron data and Fermi-LAT measurement of gamma-ray from the dwarf galaxies, we find the dark shower could open a new region of sensitivity that could not be probed before.

We analyze the scenario within the next to minimal supersymmetric Standard Model, where the lightest supersymmetric particle is singlinolike neutralino. By systematically considering various possible admixtures in the electroweakino sector, we classify regions of parameter space where the next to lightest supersymmetric particle is a long-lived electroweakino while remaining consistent with constraints from flavor physics, dark matter direct detection, and collider data. We identify viable cascade decay modes featuring the long-lived next to lightest supersymmetric particle for directly produced chargino-neutralino pairs, thus, leading to displaced vertex signatures at the high luminosity LHC (HL-LHC). We construct a track-based analysis in order to uncover such scenarios at the HL-LHC and analyze their discovery potential. We show that through such focused searches for the long-lived particles at the HL-LHC, one can probe regions of the electroweakino parameter space that are otherwise challenging.

Inflaton seeds nonthermal leptogenesis by pair-producing right-handed neutrinos in the seesaw model. We show that the inevitable graviton bremsstrahlung associated with inflaton decay can be a unique probe of nonthermal leptogenesis. The emitted gravitons contribute to a high-frequency stochastic gravitational waves background with a characteristic fall-off below the peak frequency. Besides leading to a lower bound on the frequency ($f\gtrsim {10}^{11}\mathrm{Hz}$), the seesaw-perturbativity condition makes the mechanism sensitive to the lightest neutrino mass. For an inflaton mass close to the Planck scale, the gravitational waves contribute to sizeable dark radiation, which is within the projected sensitivity limits of future experiments such as CMB-S4 and CMB-HD.

In the gradient flow method of lattice gauge theory, coarse graining is performed so as to reduce the action, and as the coarse graining progresses, the field strength becomes very small. However, the confinement property that particles interact strongly is not lost by the gradient flow. It is seemingly mysterious, and something stable against coarse graining is expected to be behind the nature of confinement. By performing Monte Carlo simulations of $U(1)$ lattice gauge theory, we discuss the relationship between the gradient flow and magnetic monopoles created by the compactness of the $U(1)$ gauge group. Many magnetic monopoles are generated in the confinement phase but not so many in the deconfinement phase. Since the monopole is a kind of topological quantity, the number of monopoles does not change much by the coarse graining. To investigate why the confinement properties are not lost by the gradient flow, we computed Wilson loops and Polyakov loops separating them into the field strength and the monopole contributions. We found that the field strength, which decreases with the gradient flow, does not affect confinement properties, and the monopole and the confinement properties are strongly related. Furthermore, we discuss the relationship between the magnetic monopole and the center symmetry, which is the symmetry broken by the confinement phase transition.

Two methodologies have been presented in the literature which connect relativistic three-particle scattering amplitudes with lattice QCD spectra—the “relativistic effective field theory” approach and the “finite-volume unitarity” method. While both methods have been shown to be equivalent in various works, it has not been shown how to arrive at the relativistic effective field theory results directly from $S$-matrix unitarity. In this work, we provide a simple proof of the relativistic effective field theory form of the scattering equations directly from unitarity. Motivated by the finite-volume unitarity approach, we then postulate a set of quantization conditions which relate the finite-volume energy spectra to the $K$-matrices which drive the short-distance physics in the scattering equations, obtaining all previously known results for three identical particles. This work also presents new relations which provide a new pathway to generalize the results to arbitrary systems.

We calculate the spectrum of gluons sourced by the branching of an energetic quark in the presence of an inhomogeneous QCD medium, focusing on the soft radiation limit. We take into account multiple soft interactions between the partons and matter, treating the transverse variations of its parameters within a gradient expansion. Thus, we derive the general form of the medium induced spectrum up to the first order in gradients, and consider its simplifying limits. In particular, we show that to the leading order in matter gradients and using the harmonic approximation for the scattering potential, the full gluon spectrum can be written in a compact closed form suitable for numerical evaluation. The final gluon transverse momentum tends to align along the anisotropy direction, resulting in a nontrivial azimuthal pattern in the jet substructure.

We analyze Mueller’s QCD dipole wave function evolution in the double logarithm approximation (DLA). Using complex analytical methods, we show that the distribution of the dipole in the wave function (gluon multiplicity distribution) asymptotically satisfies the Koba-Nielsen-Olesen (KNO) scaling, with a nontrivial scaling function $f(z)$ with $z=\frac{n}{\overline{n}}$. The scaling function decays exponentially as $2(2.55{)}^{2}z{e}^{-\frac{z}{0.3917}}$ at large $z$, while its growth is log-normal as $e^{-\frac{1}{2}{\ln }^{2}z}$ for small $z$. A detailed analysis of the Fourier-Laplace transform of $f(z)$ allows for performing the inverse Fourier transform and accessing the nonasymptotic bulk region around the peak. The bulk and asymptotic results are shown to be in good agreement with the measured hadronic multiplicities in DIS, as reported by the H1 Collaboration at HERA in the region of large $Q^2$. A numerical tabulation of $f(z)$ is included. Remarkably, the same scaling function is found to emerge in the resummation of double logarithms in the evolution of jets. Using the generating function approach, we show why this is the case. The absence of KNO scaling in noncritical and super-renormalizable theories is briefly discussed. We also discuss the universal character of the entanglement entropy in the KNO scaling limit and its measurement using the emitted multiplicities in DIS and $e^{+}{e}^{-}$ annihilation.

We investigate the relativistic scattering of three identical scalar bosons interacting via pair-wise interactions. Extending techniques from the nonrelativistic three-body scattering theory, we provide a detailed and general prescription for solving and analytically continuing integral equations describing the three-body reactions. We use these techniques to study a system with zero angular momenta described by a single scattering length leading to a bound state in a two-body subchannel. We obtain bound-state-particle and three-particle amplitudes in the previously unexplored kinematical regime; in particular, for real energies below elastic thresholds and complex energies in the physical and unphysical Riemann sheets. We extract positions of three-particle bound-states that agree with previous finite-volume studies, providing further evidence for the consistency of the relativistic finite-volume three-body quantization conditions. We also determine previously unobserved virtual bound states in this theory. Finally, we find numerical evidence of the breakdown of the two-body finite-volume formalism in the vicinity of the left-hand cuts and argue for the generalization of the existing formalism.

A study of anomalous couplings of the Higgs boson to vector bosons and fermions is presented. The data were recorded by the CMS experiment at a center-of-mass energy of pp collisions at the LHC of 13 TeV and correspond to an integrated luminosity of $138{\mathrm{fb}}^{-1}$. The study uses Higgs boson candidates produced mainly in gluon fusion or electroweak vector boson fusion at the LHC that subsequently decay to a pair of $\tau$ leptons. Matrix-element and machine-learning techniques were employed in a search for anomalous interactions. The results are combined with those from the four-lepton and two-photon decay channels to yield the most stringent constraints on anomalous Higgs boson couplings to date. The pure $CP$-odd scenario of the Higgs boson coupling to gluons is excluded at 2.4 standard deviations. The results are consistent with the standard model predictions.

Group field theories are quantum field theories built on groups. They can be seen as a tool to generate topological state-sums or quantum gravity models. For four dimensional manifolds, different arguments have pointed toward 2-groups (such as crossed modules) as the relevant symmetry structure to probe four dimensional topological features. Here, we introduce a group field theory built on crossed modules which generate a four dimensional topological model, as we prove that the Feynman diagram amplitudes can be related by Pachner moves. This model is presumably the dual version of the Yetter-Mackaay model.

The cumulants of baryon number fluctuations serve as a good probe for experimentally exploring the QCD phase diagram at finite density, giving rise to characteristic fluctuation patterns associated with a possible critical endpoint (CEP). We compute the higher-order baryon number susceptibilities at finite temperature and baryon chemical potential using a holographic QCD model to address the nonperturbative aspect of strongly coupled QCD matter. The model can accurately confront lattice QCD data on a quantitative level and the location of the CEP is found to fall within the range accessible to upcoming experimental measurements. The baryon number susceptibilities up to the twelfth order are computed, and the collision energy dependence of different ratios of these susceptibilities is examined along the chemical freeze-out line. The holographic results show quantitative agreement with experimental data and the functional renormalization group results in a large collision energy range, with all ratios exhibiting a peak structure around 5–10 GeV. The mismatching between our holographic results with experimental data for sufficiently low-collision energy is possibly due to nonequilibrium effects and complex experimental environments. The future experiments with measurements in the low-collision energy range $\sqrt{S_{NN}}\approx 1–10\mathrm{GeV}$ and reduced experimental uncertainty could reveal more nonmonotonic behavior signals which can be used to locate the CEP.

In $\mathrm{AdS}/\mathrm{CFT}$, the entanglement wedge $\mathrm{EW}(B)$ is the portion of the bulk geometry that can be reconstructed from a boundary region $B$; in other words, $\mathrm{EW}(B)$ is the hologram of $B$. We extend this notion to arbitrary spacetimes. Given any gravitating region $a$, we define a max- and a min-entanglement wedge, $e_{\max }(a)$ and $e_{\min }(a)$, such that $e_{\min }(a)\supset e_{\max }(a)\supset a$. Unlike their analogs in $\mathrm{AdS}/\mathrm{CFT}$, these two spacetime regions can already differ at the classical level, when the generalized entropy is approximated by the area. All information outside $a$ in $e_{\max }(a)$ can flow inwards towards $a$, through quantum channels whose capacity is controlled by the areas of intermediate homology surfaces. In contrast, all information outside $e_{\min }(a)$ can flow outwards. The generalized entropies of appropriate entanglement wedges obey strong subadditivity, suggesting that they represent the von Neumann entropies of ordinary quantum systems. The entanglement wedges of suitably independent regions satisfy a no-cloning relation. This suggests that it may be possible for an observer in $a$ to summon information from spacelike related points in $e_{\max }(a)$, using resources that transcend the semiclassical description of $a$.

The quantum null energy condition (QNEC) is usually stated as a bound on the expectation value of null components of the stress-energy tensor at a point in terms of second null shape variations of the entanglement entropy at the same point. It can be recast as the statement that the sign of the second null shape variation of the relative entropy of any state with respect to the vacuum is positive. Using instead a Rényi generalization of relative entropy, called sandwiched Rényi divergence (SRD), leads to what is termed the Rényi QNEC: The second null shape variation of SRD of any state with respect to the vacuum is positive. In this work, we prove the Rényi QNEC for free and superrenormalizable fermionic quantum field theories in spacetime dimensions greater than 2 using null quantization, for the case where the Rényi parameter $n>1$. We end with comments on multiple possible generalizations.

There is increasing interest in discrete or “pixelated” spacetime models as a foundation for a satisfactory theory of quantum gravity. If spacetime possesses a cellular structure, there should be observable consequences; for example, the vacuum becomes a dispersive medium. Of obvious interest are the implications for the thermodynamic properties of quantum black holes. As a first step to investigating that topic, we present here a calculation of the response of a uniformly accelerating particle detector in the (modified) quantum vacuum of a background pixelated spacetime, which is well known to mimic some features of the Hawking effect. To investigate the detector response we use the standard DeWitt’s treatment, with a two-point function modified to incorporate the dispersion. We use dispersion relations taken from the so-called doubly special relativity (DSR) and Hořava-Lifshitz gravity. We find that the correction terms retain the Planckian nature of particle detection, but only for propagation faster than the speed of light, a possibility that arises in this treatment because the dispersion relations violate Lorentz invariance. A fully Lorentz-invariant theory requires additional features; however, we believe the thermal response will be preserved in the more elaborate treatment.