In the framework of the dense-dilute color glass condensate approach, we study fluctuations in the multiplicity of produced particles in $p-A$ collisions. We show that the leading effect that drives the fluctuations is the Bose enhancement of gluons in the proton wave function. We explicitly calculate the moment generating function that resums the effects of Bose enhancement. We show that it can be understood in terms of the Liouville effective action for the composite field, which is identified with the fluctuating density, or saturation momentum of the proton. The resulting probability distribution turns out to be very close to the $\gamma$ distribution. We also calculate the first correction to this distribution, which is due to pairwise Hanbury Brown–Twiss correlations of produced gluons.

We provide the most up-to-date predictions for the top-quark charge asymmetry $A_{\mathrm{C}}$ at the LHC with a center-of-mass energy of 8 TeV. Our result is accurate at the NNLO level in the strong interactions and at the complete-NLO level in both the strong and electroweak interactions. We present results for the inclusive $A_{\mathrm{C}}$, several differential asymmetries as well as the $p_{T,t\overline{t}}$ and $m_{t\overline{t}}$ cumulative asymmetries. Similarly to the Tevatron forward-backward asymmetry $A_{\mathrm{FB}}$, both NNLO QCD and NLO EW corrections to $A_{\mathrm{C}}$ are found to be significant. The inclusion of higher-order corrections reduces the residual scale dependence in the predicted $A_{\mathrm{C}}$. The pattern of higher-order corrections indicates good perturbative control over these observables. We conclude that at present there is nearly uniform agreement between standard model predictions and LHC measurements across all $A_{\mathrm{C}}$-related observables. All previously published differential $A_{\mathrm{FB}}$ predictions at the Tevatron are updated to the same accuracy.

A certain identification of points in a planar Schwarzschild-anti de Sitter (AdS) black hole generates a four-dimensional static black string. In turn, a rotating black string can be obtained from a static one by means of a local boost along the compact direction. On the basis of the gauge/gravity duality, these black strings are dual to rotating thermal states of a strongly interacting conformal field theory (CFT) that lives on a cylinder. In this work, we obtain the complete quasinormal mode (QNM) spectrum of the gravitational perturbations of rotating black strings. Analytic solutions for the dispersion relations are found in the hydrodynamic limit, characterized by fluctuations with wave number and frequency much smaller than the Hawking temperature of the string (or the temperature of the CFT in the dual description). We obtain these dispersion relations both by studying the gravitational perturbations of rotating black strings and by investigating relativistic wave vectors in a moving fluid living on the boundary of the AdS spacetime. Relativistic effects like the Doppler shift of the frequencies, wavelength contraction, and dilation of the thermalization time are shown explicitly in such a regime. The numerical solutions for the fundamental QNMs show a crossover (a transition) from a hydrodynamic-like behavior to a linear relativistic scaling for large wave numbers. Additionally, we find a new family of QNMs which are purely damped in the zero wave number limit and that does not follow as a continuation of QNMs of the static black string, but that appears to be closely related to the algebraically special perturbation modes.

We consider the dependence of the recently proposed action/complexity duality conjecture on time and on the underlying topology of the bulk spacetime. For the former, we compute the dependence of the CFT complexity on a boundary temporal parameter and find it to be commensurate with corresponding computations carried out in terms of the rate of change of the bulk action on a Wheeler deWitt (WDW) patch. For the latter, we compare the action/complexity relation for ($d+1$)-dimensional Schwarzschild AdS black holes to those of their geon counterparts, obtained via topological identification in the bulk spacetime. The complexity/action duality relation holds in both cases, but with the proportionality changed by a factor of 4, indicating sensitivity to spacetime topology.

We study properties of heavy-light-heavy three-point functions in two-dimensional conformal field theories by using the modular invariance of two-point functions on a torus. We show that the result is nontrivially consistent with the condition of eigenstate thermalization hypothesis. We also study the open-closed duality of cylinder amplitudes and derive behaviors of disk one-point functions.

We consider the information metric and Berry connection in the context of noncommutative matrix geometry. We propose that these objects give a new method of characterizing the fuzzy geometry of matrices. We first give formal definitions of these geometric objects and then explicitly calculate them for the well-known matrix configurations of fuzzy $S^2$ and fuzzy $S^4$. We find that the information metrics are given by the usual round metrics for both examples, while the Berry connections coincide with the configurations of the Wu-Yang monopole and the Yang monopole for fuzzy $S^2$ and fuzzy $S^4$, respectively. Then, we demonstrate that the matrix configurations of fuzzy $S^n$ ($n=2$, 4) can be understood as images of the embedding functions $S^n\to {\mathbf{R}}^{n+1}$ under the Berezin-Toeplitz quantization map. Based on this result, we also obtain a mapping rule for the Laplacian on fuzzy $S^4$.

In general relativity, gravity is universally attractive, a feature embodied by the Raychaudhuri equation which requires that the expansion of a congruence of geodesics is always non-increasing, as long as matter obeys the strong or weak energy conditions. This behavior of geodesics is an important ingredient in general proofs of singularity theorems, which show that many spacetimes are singular in the sense of being geodesically incomplete and suggest that general relativity is itself incomplete. It is possible that alternative theories of gravity, which reduce to general relativity in some limit, can resolve these singularities, so it is of interest to consider how the behavior of geodesics is modified in these frameworks. We compute the leading corrections to the Raychaudhuri equation for the expansion due to models in string theory, braneworld gravity, $f(R)$ theories, and loop quantum cosmology, for cosmological and black hole backgrounds, and show that while in most cases geodesic convergence is reinforced, in a few cases terms representing repulsion arise, weakening geodesic convergence and thereby the conclusions of the singularity theorems.

A new form time crystal has been proposed, and some of its consequences have been studied. The model is a generalization of the Friedmann-Robertson-Walker (FRW) cosmology endowed with noncommutative geometry corrections. In the minisuperspace approach, the scale factor undergoes the time periodic behavior, or Sisyphus dynamics, which allows us to interpret this cosmological time crystal as a physically motivated toy model to simulate the cyclic universe. Analyzing our model purely from the time crystal perspective reveals many novelties such as a complex singularity structure (more complicated than the previously encountered swallowtail catastrophe) and a richer form of Sisyphus dynamics. In the context of cosmology, the system can serve as a toy model in which, apart from inducing a form of the cyclic universe feature, it is possible to generate an arbitrarily small positive effective cosmological constant. We stress that the model is purely geometrical without introduction of matter degrees of freedom (d.o.f.).

We use the requirement of diffeomorphism invariance in the Bianchi I context to derive the form of the quantum Hamiltonian constraint. After imposing the correct classical behavior and making a certain minimality assumption, together with a certain restriction to “planar loops,” we then obtain a unique expression for the quantum Hamiltonian operator for Bianchi I to both leading and subleading orders in $\hslash$. Specifically, this expression is found to exactly match the form proposed by Ashtekar and Wilson-Ewing in the loop quantum cosmology (LQC) literature. Furthermore, by using the projection map from the quantum states of the Bianchi I model to the states of the isotropic model, we constrain the dynamics also in the homogeneous isotropic case, and obtain, again to both leading and subleading order in $\hslash$, a quantum constraint which exactly matches the standard “improved dynamics” of Ashtekar, Pawlowski and Singh. This result in the isotropic case does not require a restriction to planar loops, but only the minimality assumption. Our results strengthen confidence in LQC dynamics and its observational predictions as consequences of more basic fundamental principles. Of the assumptions made in the isotropic case, the only one not rigidly determined by physical principle is the minimality principle; our work also shows the exact freedom allowed when this assumption is relaxed.

The EDGES experiment has recently measured an anomalous global 21-cm spectrum due to hydrogen absorptions at redshifts of about $z\sim 17$. Model independently, the unusually low temperature of baryons probed by this observable sets strong constraints on any physical process that transfers energy into the baryonic environment at such redshifts. Here, we make use of the 21-cm spectrum to derive bounds on the energy injection due to a possible population of $\mathcal{O}(1–100)M_{\odot }$ primordial black holes, which induce a wide spectrum of radiation during the accretion of the surrounding gas. After calculating the total radiative intensity of a primordial black hole population, we estimate the amount of heat and ionizations produced in the baryonic gas and compute the resulting thermal history of the Universe with a modified version of RECFAST code. Finally, by imposing that the temperature of the gas at $z\sim 17$ does not exceed the indications of EDGES, we constrain the possible abundance of primordial black holes. Depending on uncertainties related to the accretion model, we find that $\mathcal{O}(10)M_{\odot }$ primordial black holes can only contribute to a fraction $f_{\mathrm{PBH}}<(1–{10}^{-3})$ of the total dark matter abundance.

We show how the distances to binary black holes measured in gravitational wave observations with ground-based interferometers can be used to constrain the redshift-distance relation and, thereby, measure the Hubble constant ($H_0$). Gravitational wave observations of stellar-mass binary black holes are not expected to be accompanied by any electromagnetic event that may help in accessing their redshifts. We address this deficiency by using an optical catalog to get the distribution of galaxies in redshift. Assuming that the clustering of the binaries is correlated with that of the galaxies, we propose using that correlation to measure $H_0$. We show that by employing this method on simulated data obtained for second-generation networks comprising at least three detectors, e.g., the advanced LIGO–advanced VIRGO network, one can measure $H_0$ with an accuracy of $\sim 8\%$ with detection of a reference population of 25 binaries, each with black holes of mass $10M_{\odot }$. As expected, with third-generation detectors like the Einstein telescope (ET), which will measure distances much more accurately and to greater depths, one can obtain better estimates for $H_0$. Specifically, we show that with 25 observations, the ET can constrain $H_0$ to an accuracy of $\sim 7\%$. This method can also be used to estimate other cosmological parameters like the matter density ${\mathrm{\Omega }}_m$ and the dark energy equation of state.

A signal of high-energy extraterrestrial neutrinos from unknown source(s) was recently discovered by the IceCube experiment. Neutrinos are always produced together with $\gamma$-rays, but the $\gamma$-ray flux from extragalactic sources is suppressed due to attenuation in the intergalactic medium. We report the discovery of a $\gamma$-ray excess at high galactic latitudes starting at energies 300 GeV in the data of the Fermi telescope. We show that the multi-TeV $\gamma$-ray diffuse emission has spectral characteristics at both low and high galactic latitudes compatible with those of the IceCube high neutrino signal in the same sky regions. This suggests that these $\gamma$-rays are the counterpart of the IceCube neutrino signal, implying that a sizable part of the IceCube neutrino flux originates from the Milky Way. We argue that the diffuse neutrino and $\gamma$-ray signal at high galactic latitudes originates either from previously unknown nearby cosmic ray “PeVatron” source(s), an extended galactic cosmic ray halo or from decays of heavy dark matter particles.

We estimate the gravitational radiation signature of the electron/positron annihilation-driven neutrino burst accompanying the asymmetric collapse of an initially hydrostatic, radiation-dominated supermassive object suffering the Feynman-Chandrasekhar instability. An object with a mass $5\times {10}^4{M}_{\odot }<M<5\times {10}^5{M}_{\odot }$, with primordial metallicity, is an optimal case with respect to the fraction of its rest mass emitted in neutrinos as it collapses to a black hole: lower initial mass objects will be subject to scattering-induced neutrino trapping and consequently lower efficiency in this mode of gravitational radiation generation, while higher masses will not get hot enough to radiate significant neutrino energy before producing a black hole. The optimal case collapse will radiate several percent of the star’s rest mass in neutrinos and, with an assumed small asymmetry in temperature at peak neutrino production, produces a characteristic linear memory gravitational wave burst signature. The time scale for this signature, depending on redshift, is $\sim 1$ to 10 s, optimal for proposed gravitational wave observatories like DECIGO. Using the response of that detector, and requiring a signal-to-noise ratio $\mathrm{SNR}>5$, we estimate that collapse of a $\sim 5\times {10}^4{M}_{\odot }$ supermassive star could produce a neutrino burst-generated gravitational radiation signature detectable to redshift $z\lesssim 7$. With the envisioned ultimate DECIGO design sensitivity, we estimate that the linear memory signal from these events could be detectable with $\mathrm{SNR}>5$ to $z\lesssim 13$.

One of the uncertainties in the interpretation of ultrahigh energy cosmic ray data comes from the hadronic interaction models used for air shower Monte Carlo (MC) simulations. The number of muons observed at the ground from ultrahigh energy cosmic ray–induced air showers is expected to depend upon the hadronic interaction model. One may therefore test the hadronic interaction models by comparing the measured number of muons with the MC prediction. In this paper, we present the results of studies of muon densities in ultrahigh energy extensive air showers obtained by analyzing the signal of surface detector stations which should have high muon purity. The muon purity of a station will depend on both the inclination of the shower and the relative position of the station. In seven years’ data from the Telescope Array experiment, we find that the number of particles observed for signals with an expected muon purity of $\sim 65\%$ at a lateral distance of 2000 m from the shower core is $1.72\pm 0.10(\mathrm{stat})\pm 0.37(\mathrm{syst})$ times larger than the MC prediction value using the QGSJET II-03 model for proton-induced showers. A similar effect is also seen in comparisons with other hadronic models such as QGSJET II-04, which shows a $1.67\pm 0.10\pm 0.36$ excess. We also studied the dependence of these excesses on lateral distances and found a slower decrease of the lateral distribution of muons in the data as compared to the MC, causing larger discrepancy at larger lateral distances.

We promote the open-closed string map, originally formulated by Seiberg & Witten, to a solution generating prescription in generalized supergravity. The approach hinges on a knowledge of an antisymmetric bivector $\mathrm{\Theta }$, built from antisymmetric products of Killing vectors, which is specified by the equations of motion. In the cases we study, the equations of motion reproduce the classical Yang-Baxter equation (CYBE) and $\mathrm{\Theta }$ is the most general $r$-matrix solution. Our work generalizes Yang-Baxter deformations to non-coset spaces and unlocks gravity as a means to classify $r$-matrix solutions to the CYBE.

We revisit the “interpolating formula” proposed in our previous publication. It allows one to calculate the $0\nu \beta \beta$-decay half-life for arbitrary neutrino mass without the involvement of the complicated results for nuclear matrix elements (NMEs) obtained within specific nuclear structure models. The formula derives from the finding that the value of a properly normalized ratio of the NMEs for the light and heavy neutrino mass mechanisms weakly depends on the isotope. From this fact, it follows, in particular, that the light and heavy neutrino mass mechanisms can hardly be distinguished in a model-independent way searching for $0\nu \beta \beta$ decay of different nuclei. Here, we show that this formula holds for all the known nuclear structure approaches. We give a mathematical justification of our results examining analytical properties of the NMEs. We also consider several simplified benchmark scenarios within left-right symmetric models and analyze the conditions for the dominance of the light or heavy neutrino mass mechanisms in $0\nu \beta \beta$ decay.

Despite the current absence of new-physics signals at the LHC, a $Z^{\prime }$ boson with $m_{Z^{\prime }}\sim 100\mathrm{GeV}$ could still emerge via Drell-Yan (DY) production, $q\overline{q}\to Z^{\prime }\to {\mu }^{+}{\mu }^{-}$, in the next few years. To unravel the nature of the $Z^{\prime }$ coupling, we utilize the $c$- and $b$-tagging algorithms developed by ATLAS and CMS to investigate $cg\to c{Z}^{\prime }$ at the 14 TeV LHC. While light-jet contamination can be eliminated, mistagged $b$ jets cannot be rejected in any of the tagging schemes we adopt. On the other hand, for nonzero $bb{Z}^{\prime }$ coupling, far superior $b$ tagging could discover the $bg\to b{Z}^{\prime }$ process, where again light-jet mistagging can be ruled out, but mistagged $c$ jets cannot yet be excluded. Provided that DY production is discovered soon enough, we find that a simultaneous search for $cg\to c{Z}^{\prime }$ and $bg\to b{Z}^{\prime }$ can conclusively discern the nature of the $Z^{\prime }$ couplings involved.

The eigenvalue spectrum $\rho (\lambda )$ of the Dirac operator is numerically calculated in lattice QCD with $2+1$ flavors of dynamical domain-wall fermions. In the high-energy regime, the discretization effects become significant. We subtract them at the leading order and then take the continuum limit with lattice data at three lattice spacings. Lattice results for the exponent $\partial \ln \rho /\partial \ln \lambda$ are matched to continuum perturbation theory, which is known up to $O({\alpha }_s^4)$, to extract the strong coupling constant ${\alpha }_s$.

The Reactor Experiment for Neutrino Oscillation (RENO) has been taking electron antineutrino (${\overline{\nu }}_e$) data from the reactors in Yonggwang, Korea, using two identical detectors since August 2011. Using roughly 500 live days of data through January 2013 we observe 290 775 (31 514) reactor ${\overline{\nu }}_e$ candidate events with 2.8% (4.9%) background in the near (far) detector. The observed visible positron spectra from the reactor ${\overline{\nu }}_e$ events in both detectors show a discrepancy around 5 MeV with regard to the prediction from the current reactor ${\overline{\nu }}_e$ model. Based on a far-to-near ratio measurement using the spectral and rate information, we have obtained ${\sin }^{2}2{\theta }_{13}=0.082\pm 0.009(\mathrm{stat}.)\pm 0.006(\mathrm{syst}.)$ and $|\mathrm{\Delta }{m}_{ee}^2|=[2.62_{-0.23}^{+0.21}(\mathrm{stat}.{)}_{-0.13}^{+0.12}(\mathrm{syst}.)]\times {10}^{-3}{\mathrm{eV}}^2$.