Primordial gravitational waves, i.e., a background of metric perturbations sourced by the quantum inflationary fluctuations, if measured, could both provide substantial evidence for primordial inflation and shed light on physics at extremely high energy scales. In this work we focus on their propagating speed. Using an effective field theory approach we introduce a time-dependent propagating speed $c_{\mathrm{T}}(t)$ showing that also small deviations from the general relativity (GR) prediction $c_{\mathrm{T}}(t)=c$ can lead to testable consequences. We derive a set of equations that relate the propagating speed and its time dependence to the inflationary parameters and that generalize the usual slow roll consistency relations. Imposing the new generalized consistency relations and combining small and large scales data, we derive model-independent constraints on inflation with nontrivial primordial tensor speed. In particular, we constrain its scale dependence to be $d\log c_{\mathrm{T}}/d\log k=0.082_{-0.11}^{+0.047}$ at 68% C.L. while we only derive the lower bound $c_{\mathrm{T}}>0.22c$ at 95% C.L. We also constrain the tensor-to-scalar ratio at the pivot scale $k_{*}=0.05{\mathrm{Mpc}}^{-1}$ to be $r<0.0599$ at 95% C.L. in agreement with the result provided by the Planck Collaboration. Thanks to a proper small scale parametrization of the tensor spectrum we derive stringent constraints on the tensor tilt $n_{\mathrm{T}}=-0.084_{-0.047}^{+0.10}$ at 68% C.L. and on its runnings ${\alpha }_{\mathrm{T}}=d{n}_{\mathrm{T}}/d\log k=0.0141_{-0.021}^{+0.0035}$ and ${\beta }_{\mathrm{T}}=d{\alpha }_{\mathrm{T}}/d\log k=-0.0061_{-0.0014}^{+0.010}$ both at 68% C.L. Our results show a remarkable agreement with the standard slow roll predictions and prove that current data can significantly constrain deviations from GR on the inflationary energy scales.

The gravitational field of a massive object (for instance, of a galaxy group or cluster) disturbs the Hubble stream, decreasing its speed. Dependence $v(r_0)$ of the radial velocity of the stream on the present-day radius $r_0$ can be directly observed and may provide valuable information about the cluster properties. We offer an exact analytical relationship $v(r_0)$ for a spherically symmetric system.

DEAP-3600 is a single-phase liquid argon detector aiming to directly detect weakly interacting massive particles (WIMPs), located at SNOLAB (Sudbury, Canada). After analyzing data taken during the first year of operation, a null result was used to place an upper bound on the WIMP-nucleon, spin-independent, isoscalar cross section. This study reinterprets this result within a nonrelativistic effective field theory framework and further examines how various possible substructures in the local dark matter halo may affect these constraints. Such substructures are hinted at by kinematic structures in the local stellar distribution observed by the Gaia satellite and other recent astronomical surveys. These include the Gaia Sausage (or Enceladus), as well as a number of distinct streams identified in recent studies. Limits are presented for the coupling strength of the effective contact interaction operators ${\mathcal{O}}_1$, ${\mathcal{O}}_3$, ${\mathcal{O}}_5$, ${\mathcal{O}}_8$, and ${\mathcal{O}}_{11}$, considering isoscalar, isovector, and xenonphobic scenarios, as well as the specific operators corresponding to millicharge, magnetic dipole, electric dipole, and anapole interactions. The effects of halo substructures on each of these operators are explored as well, showing that the ${\mathcal{O}}_5$ and ${\mathcal{O}}_8$ operators are particularly sensitive to the velocity distribution, even at dark matter masses above $100\mathrm{GeV}/c^2$.

Gravitational wave (GW) transients from binary neutron star (BNS) coalescences can, in principle, be subject to gravitational lensing thereby increasing the amplitude and signal-to-noise ratio. We estimate the rate of lensed BNS events resolvable by LIGO and Virgo and find that it is constrained by the current nondetection of a stochastic GW background. Following closely the formalism we developed previously [R. Buscicchio et al., Phys. Rev. Lett. 125, 141102 (2020).] in the context of binary black hole lensing, we show that at current sensitivities the fraction of BNS coalescences with lensing magnifications $\mu >1.02$ is less than $\sim 7\times {10}^{-8}$ and therefore such events should not be expected in the near future. We also make predictions for projected future sensitivities.

We present predictions and projections for hadron-in-jet measurements and electron-jet azimuthal correlations at the future electron-ion collider (EIC). These observables directly probe the three-dimensional structure of hadrons, in particular, the quark transversity and Sivers parton distributions and the Collins fragmentation functions. We explore the feasibility of these experimental measurements by detector simulations and discuss detector requirements. We conclude that jet observables have the potential to enhance the three-dimensional imaging EIC program.

It has been speculated that the metric, $B$-field, and dilaton couplings in the low energy effective action of string theory at any order of ${\alpha }^{\prime }$ may be found by imposing the gauge symmetries and the $T$ duality on the effective action. This proposal can be extended to include the Ramond-Ramond (R-R) couplings as well. In this paper, we first find the dimensional reduction of the R-R fields and then perform explicitly the $T$ duality constraint on the R-R couplings at the supergravity level. Up to an overall factor, it reproduces the democratic form of the R-R couplings.

The nonlinear LC circuit dual to the Toda lattice (voltage) soliton is studied using the reductive perturbation method. It is found that the current flowing through the circuit obeys the defocusing modified Korteweg–de Vries equation with shock-wave-type (current) solitons. The current soliton spatially modulates the nonlinear inductance, equivalently the spatial modulations of electromagnetic wave velocity in the circuit, resulting in the generation of analogue black holes. Hawking radiation from the black holes is also discussed based on the tunneling models.

A two-level atom freely falling towards a Schwarzschild black hole was recently shown to detect radiation in the Boulware vacuum in an insightful paper [M. O. Scully et al., Proc. Natl. Acad. Sci. U.S.A. 115, 8131 (2018)]. The two-state atom acts as a dipole detector and its interaction with the field can be modeled using a quantum optics approach. The relative acceleration between the scalar field and the detector causes the atom to detect the radiation. In this paper, we show that this acceleration radiation is driven by the near-horizon physics of the black hole. This insight reinforces the relevance of near-horizon conformal quantum mechanics for all the physics associated with the thermodynamic properties of the black hole. We additionally highlight the conformal aspects of the radiation that is given by a Planck distribution with the Hawking temperature.

The critical formation of low-mass black holes is a historical cornerstone of numerical general relativity, with important implications in cosmology for censorship conjectures and the production of primordial black holes (PBHs). Concurrent with the surge in black hole observational physics in recent years has been an increased interest in these subjects. Critical formation is often suggested as a mechanism for PBH production, but it is possible that the existence of different types of critical processes potentially accompanying more realistic scenarios may affect this conclusion more than has been considered thus far. This paper numerically investigates, as a toy model, the interplay of multiple near-critical fields in the collapse of spherically symmetric scalar fields. It is found that a combination of type I and type II near-critical fields results in a kind of competition between their respective critical evolutions. A heuristic explanation for this phenomenon is proposed employing ideas from the theory of dynamical systems.

We present a set of localized states for an even number of Dirac fermions under Einsteinian gravity that have an infinite central redshift. Near the center of the localized state the components of the Dirac spinor and the spacetime metric all show simple power-law dependences on the radial distance; further out the fermionic wave function decays to zero and the spacetime becomes asymptotically flat. We show that this “central” solution of the equations of motion can be used to understand much of the structure observed by Finster, Smoller, and Yau [Phys. Rev. D 59, 104020 (1999)] in their numerical solutions of the same problem at finite central redshift.

We study the general infrared behavior of the power spectrum of a stochastic gravitational wave background produced by stress tensor in the form bilinear in certain dynamical degrees of freedom. We find ${\mathrm{\Omega }}_{\mathrm{GW}}\propto k^3$ for a very wide class of the sources which satisfy a set of reasonable conditions. Namely, the $k^3$ scaling is universally valid when the source term is bounded in both frequency and time, is effective in a radiation-dominated stage, and for $k$ smaller than all the physical scales associated with the source, like the peak frequency, peak width, and time duration, etc. We also discuss possible violations of these conditions and their physical implications.

The KOTO experiment has reported an excess of $K_L\to {\pi }^0\nu \overline{\nu }$ events above the Standard Model prediction, in tension with the Grossman-Nir (GN) bound. The GN bound heavily constrains new physics interpretations of an excess in this channel, but another possibility is that the observed events originate from a different process entirely: a decay of the form $K_L\to {\pi }^{0}X$, where $X$ denotes one or more new invisible species. We introduce a class of models to study this scenario with two light scalars playing the role of $X$, and we examine the possibility that the lighter of the two new states may also account for cosmological dark matter (DM). We show that this species can be produced thermally in the presence of additional interactions apart from those needed to account for the KOTO excess. Conversely, in the minimal version of the model, DM must be produced nonthermally. In this case, avoiding overproduction imposes constraints on the structure of the low-energy theory. Moreover, this requirement carries significant implications for the scale of reheating in the early Universe, generically preferring a low but observationally permitted reheating temperature of $\mathcal{O}(10\mathrm{MeV})$. We discuss astrophysical and terrestrial signatures that will allow further tests of this paradigm in the coming years.

Persistent gravitational waves from rapidly rotating neutron stars, such as those found in some young supernova remnants, may fall in the sensitivity band of the Advanced Laser Interferometer Gravitational-wave Observatory (aLIGO). Searches for these signals are computationally challenging, as the frequency and frequency derivative are unknown and evolve rapidly due to the youth of the source. A hidden Markov model (HMM), combined with a maximum-likelihood matched filter, tracks rapid frequency evolution semicoherently in a computationally efficient manner. We present the results of an HMM search targeting 12 young supernova remnants in data from Advanced LIGO’s second observing run. Six targets produce candidates that are above the search threshold and survive predefined data quality vetoes. However, follow-up analyses of these candidates show that they are all consistent with instrumental noise artifacts.

Many continuous gravitational wave searches are affected by instrumental spectral lines that could be confused with a continuous astrophysical signal. Several techniques have been developed to limit the effect of these lines by penalizing signals that appear in only a single detector. We have developed a general method, using a convolutional neural network, to reduce the impact of instrumental artifacts on searches that use the SOAP algorithm Bayley et al. [Phys. Rev. D 100, 023006 (2019)]. The method can identify features in corresponding frequency bands of each detector and classify these bands as containing a signal, an instrumental line, or noise. We tested the method against four different datasets: Gaussian noise with time gaps, data from the final run of Initial LIGO (S6) with signals added, the reference S6 mock data challenge dataset Walsh et al. [Phys. Rev. D 94, 124010 (2016)] and signals injected into data from the second advanced LIGO observing run (O2). Using the S6 mock data challenge dataset and at a 1% false alarm probability we showed that at 95% efficiency a fully automated SOAP search has a sensitivity corresponding to a coherent signal-to-noise ratio of 110, equivalent to a sensitivity depth of $10{\mathrm{Hz}}^{-1/2}$, making this automated search competitive with other searches requiring significantly more computing resources and human intervention.

The diffuse neutrino flux measured in IceCube is comparable with the ultrahigh-energy cosmic-ray (UHECR) flux, which has led to the concept of a unified origin of high-energy neutrino and UHECR backgrounds. We construct a generic unification model of sources to explain UHECR data at $\gtrsim {10}^{19}\mathrm{eV}$, and high-energy neutrinos with energies that exceed $\sim 100\mathrm{TeV}$ in the framework of photo-meson production processes, and provide general constraints on the source properties. A source environment with moderately efficient in situ production of $\gtrsim 100\mathrm{TeV}$ neutrinos with an optical depth of $0.1\lesssim {\tau }_{p\gamma }\lesssim 0.6$ must be realized to accelerate cosmic rays to ultrahigh energies. The measured fluxes of cosmic rays and neutrinos set a bound on the source luminosity and its rate density. Although the results are rather general and applicable to unknown source population, among the proposed source candidates, low-luminosity gamma-ray bursts and tidal disruption events could satisfy the requirements if the Lorentz bulk factor of plasma outflow and the equipartition parameters for cosmic rays and magnetic field are appropriately selected.

Radiative and nonradiative electron spin-flip probabilities are analyzed in both plane wave and focused laser backgrounds. We provide a simple and physically transparent description of spin dynamics in plane waves, and demonstrate that there exists a kinematic regime in which the usual leading-order perturbative hierarchy of quantum electrodynamics is reversed, and nonradiative loop effects dominate over radiative tree-level spin flips. We show that while this loop dominance becomes suppressed in focused laser pulses due to a high sensitivity to field geometry, there is nevertheless a regime in which, in principle, loop effects on spin transitions can be discerned.

Hadronic showers transfer a relevant amount of their energy to electromagnetic subshowers. We show that the generation of “secondary” dark photons in these subshowers is significant and typically dominates the production at low dark photon masses. The resulting dark photons are however substantially less energetic than the ones originating from mesons decay. We illustrate this point both semianalytically and through Monte Carlo simulations. Existing limits on vector-mediator scenarios for light dark matter are updated with the inclusion of the new production processes.

The values of the antineutron-nucleus scattering lengths, and, in particular, their imaginary parts, are needed to evaluate the feasibility of using neutron mirrors in laboratory experiments to search for neutron-antineutron oscillations. We analyze existing experimental and theoretical constraints on these values with emphasis on low-$A$ nuclei and use the results to suggest materials for the neutron-antineutron guide and to evaluate the systematic uncertainties in estimating the neutron-antineutron oscillation time. As an example, we discuss a scenario for a future neutron-antineutron oscillation experiment proposed for the European Spallation Source. We also suggest future experiments which can provide a better determination of the values of antineutron-nuclei scattering lengths.

We examine the resonant conversion of axionlike particle (ALP) or dark photon to the electromagnetic photon in the early Universe, which takes place due to the ALP-photon-dark photon oscillations in background dark photon gauge fields. It is noted that the corresponding conversion probability can have an unusual spectral feature which allows strong conversion at low frequency domain, but has negligible conversion at high frequencies above certain critical frequency which is determined by the ALP coupling to dark photon and the strength of background dark photon gauge field. We apply this scheme to heat up the 21-cm photons without affecting the cosmic microwave background, which can explain the tentative absorption signal of 21-cm photons detected recently by the EDGES experiment.

We analyze the LHC prospects for measurements of the $t\overline{t}$ pair produced exclusively in photon-photon or semiexclusively in photon-Pomeron and Pomeron-Pomeron processes using protons tagged in forward proton detectors on both sides of the interaction point. These processes are interesting from the point of view of a possible measurement of the top quark mass and constraining models used in beyond the Standard Model physics. Focusing on the semileptonic channel, $t\overline{t}\to jjbl{\nu }_l\overline{b}$, making use of the exclusive nature of the final state, together with the use of timing information provided by forward proton detectors, relevant exclusive and inclusive backgrounds are studied in detail for different luminosity (or pileup) scenarios and found to be important for further consideration. While good prospects are found for observing the signal, the top quark mass measurement turns out not to be competitive with measurements in inclusive channels.