Initial state evolution in parton shower event generators involves parton distribution functions. We examine the probability for the system to evolve from a higher scale to a lower scale without an initial state splitting. A simple argument suggests that this probability, when multiplied by the ratio of the parton distributions at the two scales, should be independent of the parton distribution functions. We call this the PDF property. We examine whether the PDF property actually holds using pythia and deductor. We also test a related property for the deductor shower and discuss the physics behind the results.

In this paper, we discuss the exclusive photoproduction of ground and excited states of $\psi (1S,2S)$ and $\mathrm{\Upsilon }(1S,2S)$ in ultraperipheral collisions (UPCs). Using the potential model in order to obtain the vector meson wave function, we find a good agreement of our calculations with data from the LHC and HERA colliders for $J/\psi (1S,2S)$ and $\mathrm{\Upsilon }(1S)$ in $\gamma p$ collisions. We extend the calculations to the nuclear target case applying them to $AA$ UPCs with the use of the shadowing and finite coherence length effects fitted to the data. Our results are compared to the recent LHC data, in both incoherent ($J/\mathrm{\Psi }(1S)$ at 2.76 TeV) and coherent ($J/\mathrm{\Psi }(1S)$ at 2.76 and 5.02 TeV) processes. We also show the corresponding predictions for the excited states, in the hope that future measurements could provide more detailed information about the vector meson wave functions and nuclear effects.

We investigate some consequences if neutrinoless double beta decays ($0\nu \beta \beta \mathrm{s}$) of nuclei are dominated by short range interactions. To illustrate our results, we assume that $0\nu \beta \beta \mathrm{s}$ proceed mainly through short range interactions involving two-W-boson exchanges and confine ourselves to only include new scalars without new gauge interactions for the SM fermions. For the neutrino mass problem, we propose to solve it by adopting that the light neutrinos have predominantly Dirac masses and the small Majorana masses induced by the new scalars render them quasi-Dirac particles. This particular aspect of neutrinos may be detectable in the next generations of neutrino oscillation experiments and/or neutrino telescope. If so this opens a new connection between $0\nu \beta \beta$ and neutrino physics. We also note the new physics signals such as the high charged states that can be explored in hadron colliders. In particular, we find that a high energy $e^{-}{e}^{-}$ will be very useful in testing the origin of lepton number violation, which complements the $0\nu \beta \beta$ studies.

The generation of accurate neutrino-nucleus cross section models needed for neutrino oscillation experiments requires simultaneously the description of many degrees of freedom and precise calculations to model nuclear responses. The detailed calculation of complete models makes the Monte Carlo generators slow and impractical. We present exhaustive neural importance sampling, a method based on normalizing flows to find a suitable proposal density for rejection sampling automatically and efficiently, and discuss how this technique solves common issues of the rejection algorithm.

Møller scattering is one of the most fundamental processes in QED, and a variety of modern experiments require its knowledge to high precision. A recent calculation considered the radiative process at low energy, where the electron mass cannot be neglected. To test the calculation, an experiment was carried out using the Van de Graaff accelerator at the MIT High Voltage Research Laboratory. Momentum spectra at three scattering angles are reported here and compared to simulation, based on our previous calculation. Good agreement between the measurements and our calculation is observed.

Flipping a symmetry often leads to a more fundamental symmetry and new physics insight. Applying this principle to the standard model electroweak symmetry, we obtain a novel gauge symmetry, which defines dark charge besides electric charge, neutrino mass mechanism, and resultant dark parity as residual flipped symmetry. The dark parity divides the model particles into two classes: odd and even. The dark matter candidate transforms as a fermion or a scalar singlet, having a mass below the electron mass, being stabilized by the dark parity. Scenarios for consistent neutrino mass generation and dark matter relic are proposed. The nature and further implication of the flipping approach are determined.

We study (fermionic) spectral functions in two holographic models, the Gubser-Rocha-linear axion model and the linear axion model, where translational symmetry is broken by axion fields linear to the boundary coordinates (${\psi }_I=\beta {\delta }_{Ii}{x}^i$). Here, $\beta$ corresponds to the strength of momentum relaxation. The spectral function is computed by the fermionic Green’s function of the bulk Dirac equation, where a fermion mass, $m$, and a dipole coupling, $p$, are introduced as input parameters. By classifying the shape of spectral functions, we construct complete phase diagrams in ($m$, $p$, $\beta$) space for both models. We find that two phase diagrams are similar even though their background geometries are different. This similarity might be due to temperature effect, since our analysis has been done at small but finite temperature ($T/\mu =0.1$). We also find that the effect of momentum relaxation on the (spectral function) phases of two models are similar even though the effect of momentum relaxation on the dc conductivities of two models are very different. We suspect that this is because holographic fermion does not backreact to geometry in our framework.

Black holes of sufficiently large initial radius are expected to be well described by a semiclassical analysis at least until half of their initial mass has evaporated away. For a small number of spacetime dimensions, this holds as long as the black hole is parametrically larger than the Planck length. In that case, curvatures are small, and backreaction onto geometry is expected to be well described by a time-dependent classical metric. We point out that at large $D$, small curvature is insufficient to guarantee a valid semiclassical description of black holes. Instead, the strongest bounds come from demanding that the rate of change of the geometry is small and that black holes scramble information faster than they evaporate. This is a consequence of the enormous power of Hawking radiation in $D$ dimensions due to the large available phase space and the resulting minuscule evaporation times. Asymptotically, only black holes with entropies $S\ge D^{D+3}\log D$ are semiclassical. We comment on implications for realistic quantum gravity models in $D\le 26$ as well as relations to bounds on theories with a large number of gravitationally interacting light species.

We present an extension of work in an earlier paper showing high precision comparisons between black hole perturbation theory and post-Newtonian (PN) theory in their region of overlapping validity for bound, eccentric-orbit, Schwarzschild extreme-mass-ratio inspirals. As before we apply a numerical fitting scheme to extract eccentricity coefficients in the PN expansion of the gravitational wave fluxes, which are then converted to exact analytic form using an integer-relation algorithm. In this work, however, we fit to individual $lmn$ modes to exploit simplifying factorizations that lie therein. Since the previous paper focused solely on the energy flux, here we concentrate initially on analyzing the angular momentum flux to infinity. A first step involves finding convenient forms for hereditary contributions to the flux at low-PN order, analogous to similar terms worked out previously for the energy flux. We then apply the upgraded techniques to find new PN terms through 9PN order and (at many PN orders) to $e^{30}$ in the power series in eccentricity. With the new approach applied to angular momentum fluxes, we return to the energy fluxes at infinity to extend those previous results. Like before, the underlying method uses a Mathematica code based on use of the Mano-Suzuki-Takasugi (MST) function expansion formalism to represent gravitational perturbations and spectral source integration (SSI) to find numerical results at arbitrarily high precision.

With the advent of gravitational wave astronomy, searching for gravitational wave echoes from black holes (BHs) is becoming an interesting probe of their quantum nature near their horizons. Newborn BHs may be strong emitters of echoes, as they accompany large perturbations in the surrounding spacetime upon formation. Utilizing the Quantum Black Hole Seismology framework [N. Oshita et al., preceding paper, Phys. Rev. D 102, 024045 (2020)], we study the expected echoes upon BH formation resulting from neutron star mergers and failed supernovae. For BH remnants from neutron star mergers, we evaluate the consistency of these models with the recent claim on the existence of echoes following the neutron star merger event GW170817. We find that the claimed echoes in GW170817, if real, suggest that overtones contribute a significant amount of energy in the ringdown of the remnant BH. We finally discuss the detectability of echoes from failed supernovae by second and third-generation gravitational wave detectors, and find that current (future) detectors constrain physical reflectivity models for events occurring within a few Mpc (a few $\times 10\mathrm{Mpc}$). Detecting such echo signals may significantly constrain the maximum mass and equation of state of neutron stars.

Searches for gravitational wave echoes in the aftermath of mergers and/or formation of astrophysical black holes have recently opened a novel and surprising window into the quantum nature of their horizons. Similar to astro- and helioseismology, a study of the spectrum of quantum black holes provides a promising method to understand their inner structure, what we call quantum black hole seismology. We provide a detailed numerical and analytic description of this spectrum in terms of the properties of the Kerr spacetime and quantum black hole horizons, showing that it drastically differs from their classical counterparts. Our most significant findings are the following: (1) If the temperature of quantum black hole is $\lesssim 2\times$ Hawking temperature, then it will not suffer from ergoregion instability (although the bound is looser at smaller spins). (2) We find how quantum black hole spectra pinpoint the microscopic properties of quantum structure. For example, the detailed spacing of spectral lines can distinguish whether quantum effects appear through compactness (i.e., exotic compact objects) or frequency (i.e., modified dispersion relation). (3) We find out that the overtone quasinormal modes may strongly enhance the amplitude of echo in the low-frequency region. (4) We show the invariance of the spectrum under the generalized Darboux transformation of linear perturbations, showing that it is a genuine covariant observable.

We revisit the issue of the fluid description of minimally coupled scalar fields. While in a cosmological setup the interpretation of a time-evolving scalar field as a perfect fluid is well understood; the situation is more intricate when the scalar field is static but has a spatial gradient, a situation motivated by black hole perturbations in scalar-tensor theories. Then the scalar field is interpreted as either a particular imperfect fluid of type I or a superposition of a pair of leftgoing (incoming) and rightgoing (outgoing) null dusts with a perfect fluid. Finally, when the scalar gradient is null, it is equivalent to an imperfect fluid of type II, degenerating into null dust when the energy conditions are imposed. We also propose the suitable action in terms of the fluid pressure components for each case and discuss the variational principle for a generic class of minimally coupled scalar fields.

We argue that the neutrino halo, a population of neutrinos that have undergone direction-changing scattering in the stellar envelope of a core-collapse supernova (CCSNe), is sensitive to neutrino emission history through time of flight. We show that the constant time approximation, commonly used in calculating the neutrino halo, does not capture the spatiotemporal evolution of the halo neutrino population and that correcting for time of flight can produce conditions which may trigger fast neutrino flavor conversion. We also find that there exists a window of time early in all CCSNe where the neutrino halo population is sufficiently small that it may be negligible. This suggests that collective neutrino oscillation calculations which neglect the halo may be well founded at sufficiently early times.

Quark matter may appear due to a hadronic-quark transition in the core of a hybrid star. Quarkyonic matter is an approach in which both quarks and nucleons appear as quasiparticles in a crossover transition, and provides an explicit realization of early ideas concerning quark matter (e.g., the MIT bag model). This description has recently been employed by McLerran and Reddy to model chargeless (pure neutron) matter with an approach that has the virtue that the speed of sound rises quickly at a neutron-quark transition so as to satisfy observational constraints on the neutron star maximum mass ($\gtrsim 2M_{\odot }$) and the radius of a $1.4M_{\odot }$ star ($R_{1.4}\lesssim 13.5\mathrm{km}$). Traditional models involving first-order transitions result in softer pressure-energy density relations that have difficulty satisfying these constraints except with very narrow choices of parameters. We propose a variation of quarkyonic matter involving protons and leptons whose energy can be explicitly minimized to achieve both chemical and beta equilibrium, which cannot be done in the chargeless formulation. Quarkyonic stellar models are able to satisfy observed mass and radius constraints with a wide range of model parameters, avoiding the obligatory fine-tuning of conventional hybrid star models, including requiring the transition density to be very close to the nuclear saturation density. Our formulation fits experimental and theoretical properties of the nuclear symmetry energy and pure neutron matter, and contains as few as three free parameters. This makes it an ideal tool for the study of high-density matter that is an efficient alternative to piecewise polytrope or spectral decomposition methods.

We apply a fully automated extension of the $R^{*}$ operation capable of calculating higher-loop anomalous dimensions of $n$-point Green’s functions of arbitrary, possibly nonrenormalizable, local quantum field theories. We focus on the case of the $CP$-violating Weinberg operator of the Standard Model effective field theory whose anomalous dimension is so far known only at one loop. We calculate the two-loop anomalous dimension in full QCD and the three-loop anomalous dimensions in the limit of pure Yang-Mills theory. We find sizable two-loop and large three-loop corrections, due to the appearance of a new quartic group invariant. We discuss phenomenological implications for electric dipole moments and future applications of the method.

We study the sensitivity of detectors with directional sensitivity to coherent elastic neutrino-nucleus scattering ($\mathrm{CE}\nu \mathrm{NS}$), and how these detectors complement measurements of the nuclear recoil energy. We consider stopped pion and reactor neutrino sources, and use gaseous helium and fluorine as examples of detector material. We generate Standard Model predictions, and compare to scenarios that include new, light vector or scalar mediators. We show that directional detectors can provide valuable additional information in discerning new physics, and we identify prominent spectral features in both the angular and the recoil energy spectrum for light mediators, even for nuclear recoil energy thresholds as high as $\sim 50\mathrm{keV}$. Combined with energy and timing information, directional information can play an important role in extracting new physics from $\mathrm{CE}\nu \mathrm{NS}$ experiments.

First principles calculations of the form factors of baryon excitations are now becoming accessible through advances in lattice-QCD techniques. In this paper, we explore the utility of the parity-expanded variational analysis (PEVA) technique in calculating the Sachs electromagnetic form factors for excitations of the proton and neutron. We study the two lowest-lying odd-parity excitations and demonstrate that at heavier quark masses, these states are dominated by behavior consistent with constituent quark models for the $N^{*}(1535)$ and $N^{*}(1650)$, respectively. We also study the lowest-lying localized even-parity excitation and find that its form factors are consistent with a radial excitation of the ground-state nucleon. A comparison of the results from the PEVA technique with those from a conventional variational analysis exposes the necessity of the PEVA approach in baryon excited-state studies.

A constituent gluon model that is informed by recent lattice field theory is developed. The model is then used to compute hybrid strong decay widths that could be useful for the GlueX Collaboration at Jefferson Lab and the PANDA Collaboration at FAIR. Commensurately, forthcoming data from GlueX and PANDA will test the model. Widths tend to be typical of charmonia, except for those of the lightest hybrid $S$-wave multiplet. Selection rules, extensions, limitations, and applications are discussed.

We diagram the behavior of five-dimensional anti–de Sitter spacetime against horizon formation in the gravitational collapse of a scalar field, treating the scalar field mass and width of initial data as free parameters, which we call the stability phase diagram. We find that the class of stable initial data becomes larger and shifts to smaller widths as the field mass increases. In addition to classifying initial data as stable or unstable, we identify two other classes based on nonperturbative behavior. The class of metastable initial data forms a horizon over longer time scales than suggested by the lowest order perturbation theory at computationally accessible amplitudes, and irregular initial data can exhibit nonmonotonic and possibly chaotic behavior in the horizon formation times. Our results include evidence for chaotic behavior even in the collapse of a massless scalar field.

In the context of realizing de Sitter vacua and the slow-roll inflation, several no-go conditions have been found in the framework of type IIA (generalized) flux compactifications. In this article, using our recently proposed $T$-dual dictionary [P. Shukla, A dictionary for the type II non-geometric flux compactifications, arXiv:1909.07391], we translate various such type IIA no-go conditions that subsequently lead to some interesting de Sitter no-go scenarios in the presence of (non)geometric fluxes on the dual type IIB side. We also present the relevance of using $K3/{\mathbb{T}}^4$-fibered Calabi Yau threefolds in order to facilitate one particular class of the de Sitter no-go conditions. This analysis helps in refining certain corners of the vast nongeometric flux landscape for the hunt of de Sitter vacua.