This article presents an analysis and the resulting limits on light dark matter inelastically scattering off of electrons, and on dark photon and axionlike particle absorption, using a second-generation SuperCDMS high-voltage eV-resolution detector. The 0.93 g Si detector achieved a 3 eV phonon energy resolution; for a detector bias of 100 V, this corresponds to a charge resolution of 3% of a single electron-hole pair. The energy spectrum is reported from a blind analysis with 1.2 g-days of exposure acquired in an above-ground laboratory. With charge carrier trapping and impact ionization effects incorporated into the dark matter signal models, the dark matter-electron cross section ${\overline{\sigma }}_e$ is constrained for dark matter masses from 0.5 to ${10}^4\mathrm{MeV}/c^2$; in the mass range from 1.2 to $50\mathrm{eV}/c^2$ the dark photon kinetic mixing parameter $ϵ$ and the axioelectric coupling constant $g_{ae}$ are constrained. The minimum 90% confidence-level upper limits within the above-mentioned mass ranges are ${\overline{\sigma }}_e=8.7\times {10}^{-34}{\mathrm{cm}}^2$, $ϵ=3.3\times {10}^{-14}$, and $g_{ae}=1.0\times {10}^{-9}$.

Higgs bundles are a central tool used to study a range of intersecting brane systems in string compactifications. Solutions to the internal gauge theory equations of motion for the corresponding worldvolume theories of branes give rise to different low energy effective field theories. This has been heavily used in the study of M-theory on local $G_2$ spaces and F-theory on local elliptically fibered Calabi-Yau fourfolds. In this paper we show that the 3D $\mathcal{N}=1$ effective field theory defined by M-theory on a local spin(7) space unifies the Higgs bundle data associated with 4D $\mathcal{N}=1$ M- and F-theory vacua. This 3D system appears as an interface with finite thickness between different 4D vacua. We develop the general formalism of M-theory on such local spin(7) spaces and build explicit interpolating solutions. This provides a complementary local gauge theory analysis of a recently proposed approach to constructing spin(7) spaces from generalized connected sums.

We study four-dimensional (4D) systems in which parameters of the theory have position dependence in one spatial direction. In the limit where these parameters jump, this can lead to 3D interfaces supporting localized degrees of freedom. A priori, this sort of position dependence can occur at either weak or strong coupling. Demanding time-reversal invariance for $U(1)$ gauge theories with a duality group $\mathrm{\Gamma }\subset SL(2,\mathbb{Z})$ leads to interfaces at strong coupling which are characterized by the real component of a modular curve specified by $\mathrm{\Gamma }$. This provides a geometric method for extracting the electric and magnetic charges of possible localized states. We illustrate these general considerations by analyzing some 4D $\mathcal{N}=2$ theories with 3D interfaces. These 4D systems can also be interpreted as descending from a six-dimensional theory compactified on a three-manifold generated by a family of Riemann surfaces fibered over the real line. We show more generally that 6D superconformal field theories compactified on such spaces also produce trapped matter by using the known structure of anomalies in the resulting 4D bulk theories.

We consider perturbations of the four-dimensional Reissner-Nordström spacetime induced by the probe scattering of a point particle with charge and mass moving on an unbound trajectory with an asymptotically large velocity. The resulting classical radiative solutions are the gravitational and electromagnetic bremsstrahlung. We use these classical solutions to derive the universal photon and graviton soft factor contributions at the tree level, which have the same form as noted in the literature. The soft factor expressions enable us to investigate the tail contribution to the memory effect in late time gravitational and electromagnetic waveforms. We find that generically, the contribution from the charge dominates that from the mass in the late time radiation.

In general relativity without a cosmological constant, a classical theorem due to Hawking states that stationary black holes must be topologically spherical. This result is one of the several ingredients that collectively imply the uniqueness of the Kerr metric. If, however, general relativity describes gravity inexactly at high energies or over cosmological scales, Hawking’s result may not apply, and black holes with nontrivial topology may be, at least mathematically, permissible. While tests involving electromagnetic and gravitational-wave data have been used to place tight constraints on various theoretical departures from a Kerr description of astrophysical black holes, relatively little attention has been paid to topological alternatives. In this paper, we derive a new exact solution in an $f(R)$ theory of gravity which admits topologically nontrivial black holes, and calculate observables like fluorescent $\mathrm{K}\alpha$ iron-line profiles and black hole images from hypothetical astrophysical systems which house these objects, to provide a theoretical basis for new tests of black hole nature. On the basis of qualitative comparisons, we show that topologically nontrivial objects would leave a strong imprint on electromagnetic observables and can be easily distinguished from general-relativistic black holes in nearly all cases.

Along the last decades, several regular black hole (BH) solutions, i.e., singularity-free BHs, have been proposed and associated to nonlinear electrodynamics models minimally coupled to general relativity. Within this context, it is of interest to study how those nonlinear-electrodynamic-based regular BHs (RBHs) would interact with their astrophysical environment. We investigate the propagation of a massless test scalar field in the background of an electrically charged RBH solution, obtained by Eloy Ayón-Beato and Alberto García. Using a numerical approach, we compute the absorption cross section of the massless scalar field for arbitrary values of the frequency of the incident wave. We compare the absorption cross sections of the Ayón-Beato and García RBH with the Reissner-Nordström BH, showing that they can be very similar in the whole frequency regime.

We study statistical relationships between bubble walls in cosmological first-order phase transitions. We consider the conditional and joint probabilities for different points on the walls to remain uncollided at given times. We use these results to discuss space and time correlations of bubble walls and their relevance for the consequences of the transition. In our statistical treatment, the kinematics of bubble nucleation and growth is characterized by the nucleation rate and the wall velocity as functions of time. We obtain general expressions in terms of these two quantities, and we consider several specific examples and applications.

In this paper, we consider a possibility that the temperature anisotropy of cosmic microwave background (CMB) is dominantly generated by the primordial fluctuations of QCD-axion like particles under a circumstance that inflaton’s perturbation is too small to explain the CMB anisotropy. Since the axion potential is generated by acquiring its energy from radiation, the primordial fluctuations of the axion field generated in the inflation era are correlated with the CMB anisotropies. Consequently, the observations stringently constrain a model of the axion and the early Universe scenario. The following conditions must be satisfied: (i) sufficient amplitudes of the CMB anisotropy (ii) consistency with the axion isocurvature constraint and (iii) the non-Gaussianity constraint. To satisfy these conditions, a large energy fraction ${\mathrm{\Omega }}_A$ of the axion is necessary at the QCD scale when the axion-potential is generated, but simultaneously, it must become tiny at the present era due to the isocurvature constraint. Thus, an additional scenario of the early Universe, such as low scale thermal inflation, is inevitable to dilute the axions after the QCD scale. We investigate such a model and obtain its allowed parameter region.

As space expands, the energy density in black holes increases relative to that of radiation, providing us with motivation to consider scenarios in which the early Universe contained a significant abundance of such objects. In this study, we revisit the constraints on primordial black holes derived from measurements of the light element abundances. Black holes and their Hawking evaporation products can impact the era of big bang nucleosynthesis by altering the rate of expansion at the time of neutron-proton freeze-out, as well as by radiating mesons which can convert protons into neutrons and vice versa. Such black holes can thus enhance the primordial neutron-to-proton ratio, and increase the amount of helium that is ultimately produced. Additionally, the products of Hawking evaporation can break up helium nuclei, which both reduces the helium abundance and increases the abundance of primordial deuterium. Building upon previous work, we make use of modern deuterium and helium measurements to derive stringent constraints on black holes which evaporate in $t_{\mathrm{evap}}\sim {10}^{-1}$ to $\sim {10}^{13}\mathrm{s}$ (corresponding to $M\sim 6\times {10}^8$ to $\sim 2\times {10}^{13}\mathrm{g}$, assuming Standard Model particle content). We also consider how physics beyond the Standard Model could impact these constraints. Due to the gravitational nature of Hawking evaporation, the rate at which a black hole evaporates, and the types of particles that are produced through this process, depend on the complete particle spectrum. Within this context, we discuss scenarios which feature a large number of decoupled degrees of freedom ( i.e., large hidden sectors), as well as models of TeV-scale supersymmetry.

Neutrinos emitted in the coalescence of two neutron stars affect the dynamics of the outflow ejecta and the nucleosynthesis of heavy elements. In this work, we analyze the neutrino emission properties and the conditions leading to the growth of flavor instabilities in merger remnants consisting of a hypermassive neutron star and an accretion disk during the first 10 ms after the merger. The analyses are based on hydrodynamical simulations that include a modeling of neutrino emission and absorption effects via the “improved leakage-equilibration-absorption scheme” (ILEAS). We also examine the nucleosynthesis of the heavy elements via the rapid neutron-capture process ($r$-process) inside the material ejected during this phase. The dominant emission of ${\overline{\nu }}_e$ over ${\nu }_e$ from the merger remnant leads to favorable conditions for the occurrence of fast pairwise flavor conversions of neutrinos, independent of the chosen equation of state or the mass ratio of the binary. The nucleosynthesis outcome is very robust, ranging from the first to the third $r$-process peaks. In particular, more than ${10}^{-5}{M}_{\odot }$ of strontium are produced in these early ejecta that may account for the GW170817 kilonova observation. We find that the amount of ejecta containing free neutrons after the $r$-process freeze-out, which may power early-time UV emission, is reduced by roughly a factor of 10 when compared to simulations that do not include weak interactions. Finally, the potential flavor equipartition between all neutrino flavors is mainly found to affect the nucleosynthesis outcome in the polar ejecta within $\lesssim 30°$, by changing the amount of the produced iron-peak and first-peak nuclei, but it does not alter the lanthanide mass fraction therein.

Quantum vacuum fluctuations fundamentally limit the precision of optical measurements, such as those in gravitational-wave detectors. The injection of a conventional squeezed vacuum can be used to reduce quantum noise in the readout quadrature, but this reduction is at the cost of increasing noise in the orthogonal quadrature. For detectors near the limits imposed by quantum radiation pressure noise (QRPN), both quadratures impact the measurement, and the benefits of conventional squeezing are limited. In this paper, we demonstrate the use of a critically coupled 16 m optical cavity to diminish antisqueezing at frequencies below 90 Hz, where it exacerbates QRPN, while preserving beneficial squeezing at higher frequencies. This is called an amplitude filter cavity, and it is useful for avoiding degradation of detector sensitivity at low frequencies. The attenuation from the cavity also provides technical advantages such as mitigating backscatter.

Vacuum quantum fluctuations impose a fundamental limit on the sensitivity of gravitational-wave interferometers, which rank among the most sensitive precision measurement devices ever built. The injection of conventional squeezed vacuum reduces quantum noise in one quadrature at the expense of increasing noise in the other. While this approach improved the sensitivity of the Advanced LIGO and Advanced Virgo interferometers during their third observing run (O3), future improvements in arm power and squeezing levels will bring radiation pressure noise to the forefront. Installation of a filter cavity for frequency-dependent squeezing provides broadband reduction of quantum noise through the mitigation of this radiation pressure noise, and it is the baseline approach planned for all of the future gravitational-wave detectors currently conceived. The design and operation of a filter cavity requires careful consideration of interferometer optomechanics as well as squeezing degradation processes. In this paper, we perform an in-depth analysis to determine the optimal operating point of a filter cavity. We use our model alongside numerical tools to study the implications for filter cavities to be installed in the upcoming “$\mathrm{A}+$” upgrade of the Advanced LIGO detectors.

Based on AdS/CFT correspondence, we build a deep neural network to learn black hole metrics from the complex frequency-dependent shear viscosity. The network architecture provides a discretized representation of the holographic renormalization group flow of the shear viscosity and can be applied to a large class of strongly coupled field theories. Given the existence of the horizon and guided by the smoothness of spacetime, we show that Schwarzschild and Reissner-Nordström metrics can be learned accurately. Moreover, we illustrate that the generalization ability of the deep neural network can be excellent, which indicates that by using the black hole spacetime as a hidden data structure, a wide spectrum of the shear viscosity can be generated from a narrow frequency range. These results are further generalized to an Einstein-Maxwell-dilaton black hole. Our work might not only suggest a data-driven way to study holographic transports but also shed some light on holographic duality and deep learning.

We apply the general formalism derived by Penalva et al. [Phys. Rev. D 101, 113004 (2020)] to the semileptonic decay of pseudoscalar mesons containing a $b$ quark. While present $\overline{B}\to D^{(*)}$ data give the strongest evidence in favor of lepton flavor universality violation, the observables that are normally considered are not able to distinguish between different new physics (NP) scenarios. In the above reference we discussed the relevant role that the various contributions to the double differential decay widths $d^2\mathrm{\Gamma }/(d\omega d\cos {\theta }_{\ell })$ and $d^2\mathrm{\Gamma }/(d\omega d{E}_{\ell })$ could play to this end. Here $\omega$ is the product of the two hadron four-velocities, ${\theta }_{\ell }$ is the angle made by the final lepton and final hadron three-momenta in the center of mass of the final two-lepton system, and $E_{\ell }$ is the final charged lepton energy in the laboratory system. The formalism was applied by Penalva et al. to the analysis of the ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c$ semileptonic decay, showing the new observables were able to tell apart different NP scenarios. Here we analyze the ${\overline{B}}_c\to {\eta }_c\tau {\overline{\nu }}_{\tau }$, ${\overline{B}}_c\to J/\psi \tau {\overline{\nu }}_{\tau }$, $\overline{B}\to D\tau {\overline{\nu }}_{\tau }$ and $\overline{B}\to D^{*}\tau {\overline{\nu }}_{\tau }$ semileptonic decays. We find that, as a general rule, the ${\overline{B}}_c\to J/\psi$ observables, even including $\tau$ polarization, are less optimal for distinguishing between NP scenarios than those obtained from ${\overline{B}}_c\to {\eta }_c$ decays, or those presented by Penalva et al. for the related ${\mathrm{\Lambda }}_b\to {\mathrm{\Lambda }}_c$ semileptonic decay. Finally, we show that $\overline{B}\to D$ and ${\overline{B}}_c\to {\eta }_c$, and $\overline{B}\to D^{*}$ and ${\overline{B}}_c\to J/\psi$ decay observables exhibit similar behaviors.

We applied a recently published modified Fock-Schwinger (MFS) method to find the exact solution of the propagator equation for a charged vector boson in the presence of a constant magnetic field directly in the momentum space as a sum over Landau levels in arbitrary $\xi$-gauge. In contrast to the standard approaches for finding propagators, MFS method demonstrated several improvements in terms of computational complexity reduction and revealed simple internal structures in intermediate and final expressions, thus allowing us to obtain new useful representations of the propagator.

In this work, we present a new set of unpolarized ($H$) and polarized ($\tilde{H}$) generalized parton distributions (GPDs) that have been determined using a simultaneous ${\chi }^2$ analysis of the nucleon axial form factor (AFF) and wide-angle Compton scattering (WACS) experimental data at the next-to-leading order (NLO) accuracy in QCD. We explore various Ansatzes presented in the literature for GPDs, which use forward parton distributions as input, and choose the ones most suited to our analysis. The experimental data included in our analysis cover a wide range of the squared transverse momentum, which is $0.025<-t<6.46{\mathrm{GeV}}^2$. We show that the WACS data affect significantly the large $-t$ behavior of $\tilde{H}$. The polarized GPDs obtained from the simultaneous analysis of AFF and WACS data differ considerably from the corresponding ones obtained by analyzing AFF and WACS separately, and have less uncertainties. We show that the theoretical predictions obtained using our GPDs are in good agreement with the analyzed AFF and WACS data for the entire range of $-t$ studied. Finally, we obtain the impact parameter dependent parton distributions, both in an unpolarized and in a transversely polarized proton, and present them as tomography plots.

We demonstrate a novel feature of certain phase transitions in theories with large rank symmetry group that exhibit specific types of all-to-all interactions, a typical example being the matrix model description of a large-$N$ gauge theory. Recently, it has been pointed out that nontrivial features of the confinement/deconfinement transition are understood as consequences of the coexistence of the confined and deconfined phases on the group manifold describing the color degrees of freedom. While these novel features of the confinement/deconfinement transition are analogous to the two-phase coexistence at the first-order transition of more familiar local theories, various differences such as the partial breaking of the symmetry group appear due to the all-to-all interaction. In this article, we show that similar phase transitions with partially broken symmetry can exist in various examples from quantum field theory and string theory. Our examples include the deconfinement and chiral transition in QCD, Gross-Witten-Wadia transition in two-dimensional lattice gauge theory, Douglas-Kazakov transition in two-dimensional gauge theory on sphere, and black hole/black string transition. In some of these examples, we give new interpretations to previously known solutions and clarify the underlying physical mechanism governing their phase behavior.

The transversity distribution for $u$ and $d$ quarks is usually extracted from data on spin asymmetries in semi-inclusive deep inelastic scattering (SIDIS): however, due to its chiral odd nature, it has to be coupled to another chiral odd function, typically the Collins or the dihadron fragmentation function. A recent suggestion of considering SIDIS data involving ratios of spin asymmetries and avoiding a knowledge of the Collins function is briefly discussed. New measurements, involving ratios of cross sections, are suggested. They would allow a direct extraction of the transversity ratio, $h_1^{d_V}/h_1^{u_V}$. Numerical estimates are given.

We present a complete analysis of scenarios with radiatively generated neutrino masses that may occur in the minimal supersymmetric Standard Model with low-scale right-handed neutrinos. For brevity, we call such a model the ${\nu }_R\mathrm{MSSM}$. We pay particular attention to the impact of the nonrenormalization theorem of supersymmetry (SUSY) on the loop-induced neutrino masses, by performing our computations in the weak and flavor bases. In particular, we find that the smallness of the observed light neutrino masses may naturally arise due to a soft SUSY-screening effect from a nearly supersymmetric singlet neutrino sector. The profound phenomenological and cosmological implications that may originate from this screening phenomenon in the ${\nu }_R\mathrm{MSSM}$ and its minimal extensions are discussed.

Driven by the recent experimental hints of lepton-flavor-universality violation in the bottom-quark sector, we consider a simple extension of the Standard Model (SM) with an additional vector leptoquark $V_{\mathrm{LQ}}(\mathbf{3},\mathbf{1},2/3)$ and a scalar diquark $S_{\mathrm{DQ}}(\mathbf{6},\mathbf{1},4/3)$ under the SM gauge group $SU(3{)}_c\times SU(2{)}_L\times U(1{)}_Y$, in order to simultaneously explain the $b\to s{\ell }^{+}{\ell }^{-}$ (with $\ell =e$, $\mu$) and $b\to c{l}^{-}{\overline{\nu }}_l$ (with $l=e$, $\mu$, $\tau$) flavor anomalies, as well as to generate small neutrino masses through a two-loop radiative mechanism. We perform a global fit to all the relevant and up-to-date $b\to s{\ell }^{+}{\ell }^{-}$ and $b\to c{l}^{-}{\overline{\nu }}_l$ data under the assumption that the leptoquark couples predominantly to second and third-generation SM fermions. We then look over the implications of the allowed parameter space on lepton-flavor-violating $B$ and $\tau$ decay modes, such as $B_s\to l_i^{+}{l}_j^{-}$, $B\to K^{(*)}{l}_i^{+}{l}_j^{-}$, $B_s\to \varphi l_i^{+}{l}_j^{-}$, $\mathrm{\Upsilon }(nS)\to \mu \tau$, and $\tau \to \mu \gamma$, $\tau \to \mu \varphi ({\eta }^{(\prime )})$, respectively. Minimally extending this model by adding a fermion singlet $\chi (\mathbf{1},\mathbf{1},0)$ also explains the ANITA anomalous upgoing events. Furthermore, we provide complementary constraints on leptoquark and diquark couplings from high-energy collider and other low-energy experiments to test this model.