Moving cavities promise to be a suitable system for relativistic quantum information processing. It has been shown that an inertial and a uniformly accelerated one-dimensional cavity can become entangled by letting an atom emit an excitation while it passes through the cavities, but the acceleration degrades the ability to generate entanglement. We show that in the two-dimensional case the entanglement generated is affected not only by the cavity’s acceleration but also by its transverse dimension which plays the role of an effective mass.

Recently [E. Bergshoeff et al., Classical Quantum Gravity 31, 145008 (2014)], an extension of the topologically massive gravity (TMG) in $2+1$ dimensions, dubbed as minimal massive gravity (MMG), which is free of the bulk-boundary unitarity clash that inflicts the former theory and all the other known three-dimensional theories, was found. Field equations of MMG differ from those of TMG at quadratic terms in the curvature that do not come from the variation of an action depending on the metric alone. Here we show that MMG is a unique theory and there does not exist a deformation of TMG or MMG at the cubic and quartic order (and beyond) in the curvature that is consistent at the level of the field equations. The only extension of TMG with the desired bulk and boundary properties having a single massive degree of freedom is MMG.

We consider collisions of particles near generic axially symmetric extremal black holes. We examine the possibility of an indefinitely large extraction of energy (the so-called super-Penrose process) in the limit when the point of collision approaches the horizon. Three potential options are considered: fractional powers of the lapse function in the relations between the energies and the angular momenta of particles at the point of collision, collision between outgoing and ingoing particles, and collision in the ergoregion far from the horizon. It turns out in all three cases that states suitable for the super-Penrose process cannot be obtained from the previous collision of particles with finite masses and angular momenta.

We study the transmission of information and correlations through quantum fields in cosmological backgrounds. With this aim, we make use of quantum information tools to quantify the classical and quantum correlations induced by a quantum massless scalar field in two particle detectors, one located in the early universe (Alice’s) and the other located at a later time (Bob’s). In particular, we focus on two phenomena: (a) the consequences on the transmission of information of the violations of the strong Huygens principle for quantum fields, and (b) the analysis of the field vacuum correlations via correlation harvesting from Alice to Bob. We will study a standard cosmological model first and then assess whether these results also hold if we use other than the general relativistic dynamics. As a particular example, we will study the transmission of information through the big bounce, that replaces the big bang, in the effective dynamics of loop quantum cosmology.

We investigate axial quasinormal modes of realistic neutron stars in Einstein-Gauss-Bonnet-dilaton gravity. We consider eight realistic equations of state containing nuclear, hyperonic, and hybrid matter. We focus on the fundamental curvature mode and compare the results with those of pure Einstein theory. We observe that the frequency of the modes is increased by the presence of the Gauss-Bonnet-dilaton, while the impact on the damping time is typically smaller. Interestingly, we obtain that universal relations valid in pure Einstein theory still hold for Einstein-Gauss-Bonnet-dilaton gravity, and we propose a method to use these phenomenological relations to constrain the value of the Gauss-Bonnet coupling.

In effective models of loop quantum cosmology, the holonomy corrections are associated with deformations of space-time symmetries. The most evident manifestation of the deformations is the emergence of a Euclidean phase accompanying the nonsingular bouncing dynamics of the scale factor. In this article, we compute the power spectrum of scalar perturbations generated in this model, with a massive scalar field as the matter content. Instantaneous and adiabatic vacuum-type initial conditions for scalar perturbations are imposed in the contracting phase. The evolution through the Euclidean region is calculated based on the extrapolation of the time direction pointed by the vectors normal to the Cauchy hypersurface in the Lorentzian domains. The obtained power spectrum is characterized by a suppression in the IR regime and oscillations in the intermediate energy range. Furthermore, the speculative extension of the analysis in the UV reveals a specific rise of the power leading to results incompatible with the data.

The 2-point angular correlation function $w(\theta )$ (2PACF), where $\theta$ is the angular separation between pairs of galaxies, provides the transversal baryon acoustic oscillation (BAO) signal almost model independently. In this paper we use 409 337 luminous red galaxies in the redshift range $z=[0.440,0.555]$ obtained from the tenth data release of the Sloan Digital Sky Survey (SDSS DR10) to estimate ${\theta }_{\mathrm{BAO}}(z)$ from the 2PACF at six redshift shells. Since noise and systematics can hide the BAO signature in the $w\text{−}\theta$ plane, we also discuss some criteria to localize the acoustic bump. We identify two sources of model dependence in the analysis, namely, the value of the acoustic scale from cosmic microwave background (CMB) measurements and the correction in the ${\theta }_{\mathrm{BAO}}(z)$ position due to projection effects. Constraints on the dark energy equation-of-state parameter $\mathrm{w}(z)$ from the ${\theta }_{\mathrm{BAO}}(z)$ diagram are derived, as well as from a joint analysis with current CMB measurements. We find that the standard $\mathrm{\Lambda }\mathrm{CDM}$ model as well as some of its extensions are in good agreement with these ${\theta }_{\mathrm{BAO}}(z)$ measurements.

Starting with the relativistic Boltzmann equation for a system of particles defined by a distribution function, we have derived the virial relation for a spherical structure within an expanding background in the context of general relativity. This generalized form of the virial relation is then applied to the static case of a spherically symmetric structure to see the difference in the simplest case to the Newtonian relation. A relativistic mass-temperature relation for this simple case is also derived which can be applied to compact objects in astrophysics. Our general virial relation is then applied to the nonstatic case of a structure within an expanding universe where an extra term, usually missed in studies of structures in the presence of the dark energy, appears.

In this paper we examine the constraints dedicated LHC multilepton searches can place on $Z^{\prime }$ bosons coming from a gauged muon number minus tau number, $L_{\mu }-L_{\tau }$. As the $L_{\mu }-L_{\tau }$ gauge boson does not couple to proton constituents or electrons at tree level, the current bounds are fairly loose, especially for $M_{Z^{\prime }}\gtrsim 1\mathrm{GeV}$. For $2m_{\mu }<M_{Z^{\prime }}<M_Z/2$ we develop search strategies using the $pp\to Z\to 4\mu$ channel. The cleanliness of the final state, combined with the fact that $pp\to Z\to 4e$, $Z\to 2e2\mu$ can be used as background control samples, allow us to spot $L_{\mu }-L_{\tau }$ $Z^{\prime }$ with couplings $\mathcal{O}(10^{-3})$ times the Standard Model couplings. For lighter $Z^{\prime }$, we propose the mode $pp\to 2\mu +{\cancel{E}}_T$. The presence of missing energy means there is a wider set of backgrounds to consider in this final state, such as Drell-Yan production of leptonically decaying $\tau$ pairs; however, we find that these can be controlled with careful cuts. Combining the $4\mu$ and $2\mu +{\cancel{E}}_T$ modes, we find that with $\sim 3{\mathrm{ab}}^{-1}$ of integrated luminosity we are sensitive to couplings $g_{Z^{\prime }}\gtrsim 0.005g_1$ for $0.5\mathrm{GeV}\le M_{Z^{\prime }}\le 40\mathrm{GeV}$ and $g_{Z^{\prime }}\gtrsim 0.001g_1$ for $M_{Z^{\prime }}<2m_{\mu }$. This region includes the parameter space where $L_{\mu }-L_{\tau }$ models can ameliorate the muon $g-2$ anomaly. We repeat these analyses at a future $e^{+}{e}^{-}$ $Z$-factory, where we find improved sensitivity. Specifically, given $2.6{\mathrm{ab}}^{-1}$ of luminosity, we can exclude $g_{Z^{\prime }}\gtrsim 0.001g_1$ for $2m_{\mu }\le M_{Z^{\prime }}\le M_Z/2$.

The mass-constraining variable $M_2$, a ($1+3$)-dimensional natural successor of extremely popular $M_{T2}$, possesses an array of rich features having the ability to use on-shell mass constraints in semi-invisible production at a hadron collider. In this work, we investigate the consequence of applying a heavy resonance mass-shell constraint in the context of a semi-invisible antler decay topology produced at the LHC. Our proposed variable, under additional constraint, develops a new kink solution at the true masses. This enables one to determine the invisible particle mass simultaneously with the parent particle mass from these events. We analyze in a way to measure this kink optimally, exploring the origin and the properties of such interesting characteristics. We also study the event reconstruction capability inferred from this new variable and find that the resulting momenta are unique and well correlated with true invisible particle momenta.

A diboson excess has been observed—albeit with very limited statistical significance—in $WW$, $WZ$, and $ZZ$ final states at the LHC experiments using the accumulated 8 TeV data. Assuming that these signals are due to resonances resulting from an extended symmetry breaking sector in the standard model and exact custodial symmetry, we determine using unitarization methods the values of the relevant low-energy constants in the corresponding effective Lagrangian. Unitarity arguments also predict the widths of these resonances. We introduce unitarized form factors to allow for a proper treatment of the resonances in Monte Carlo generators and a more precise comparison with experiment.

We calculate the mean and variance of net-baryon number and net-electric charge distributions from quantum chromodynamics (QCD) using a next-to-leading order Taylor expansion in terms of temperature and chemical potentials. We compare these expansions with experimental data from STAR and PHENIX, determine the freeze-out temperature in the limit of vanishing baryon chemical potential, and, for the first time, constrain the curvature of the freeze-out line through a direct comparison between experimental data on net-charge fluctuations and a QCD calculation. We obtain a bound on the curvature coefficient, ${\kappa }_2^f<0.011$, that is compatible with lattice QCD results on the curvature of the QCD transition line.

We present results for the matrix elements of the additional $\mathrm{\Delta }S=2$ operators that appear in models of physics beyond the Standard Model (BSM), expressed in terms of four BSM $B$-parameters. Combined with experimental results for $\mathrm{\Delta }{M}_K$ and ${\epsilon }_K$, these constrain the parameters of BSM models. We use improved staggered fermions, with valence hypercubic blocking transfromation (HYP)-smeared quarks and $N_f=2+1$ flavors of “asqtad” sea quarks. The configurations have been generated by the MILC Collaboration. The matching between lattice and continuum four-fermion operators and bilinears is done perturbatively at one-loop order. We use three lattice spacings for the continuum extrapolation: $a\approx 0.09$, 0.06 and 0.045 fm. Valence light-quark masses range down to $\approx m_s^{\mathrm{phys}}/13$ while the light sea-quark masses range down to $\approx m_s^{\mathrm{phys}}/20$. Compared to our previous published work, we have added four additional lattice ensembles, leading to better controlled extrapolations in the lattice spacing and sea-quark masses. We report final results for two renormalization scales, $\mu =2$ and 3 GeV, and compare them to those obtained by other collaborations. Agreement is found for two of the four BSM $B$-parameters ($B_2$ and $B_3^{\mathrm{SUSY}}$). The other two ($B_4$ and $B_5$) differ significantly from those obtained using regularization independent momentum subtraction (RI-MOM) renormalization as an intermediate scheme, but are in agreement with recent preliminary results obtained by the RBC-UKQCD Collaboration using regularization independent symmetric momentum subtraction (RI-SMOM) intermediate schemes.

In this analysis, we present the contribution associated with the chromomagnetic dipole operator ${\mathcal{O}}_8$ to the double differential decay width $d\mathrm{\Gamma }/(d{s}_{1}d{s}_2)$ for the inclusive process $\overline{B}\to X_s\gamma \gamma$. The kinematical variables $s_1$ and $s_2$ are defined as $s_i=(p_b-q_i{)}^2/m_b^2$, where $p_b$, $q_1$, $q_2$ are the momenta of $b$ quark and two photons. This contribution (taken at tree level) is of order ${\alpha }_s$, like the recently calculated QCD corrections to the contribution of the operator ${\mathcal{O}}_7$. In order to regulate possible collinear singularities of one of the photons with the strange quark, we introduce a nonzero mass $m_s$ for the strange quark. Our results are obtained for exact $m_s$, which we interpret as a constituent mass being varied between 400 and 600 MeV. Numerically it turns out that the effect of the (${\mathcal{O}}_8$, ${\mathcal{O}}_8$) contribution to the branching ratio of $\overline{B}\to X_s\gamma \gamma$ does not exceed $+0.1\%$ for any kinematically allowed value of our physical cutoff parameter $c$, confirming the expected suppression of this contribution relative to the QCD corrections to $d{\mathrm{\Gamma }}_{77}/(d{s}_{1}d{s}_2)$.

We study the cross section for vector boson ($W^{\pm }/Z^0/{\gamma }^{*}$) production in polarized nucleon-nucleon collisions for low transverse momentum of the observed vector boson. For the case where one measures the transverse momentum and azimuthal angle of the vector bosons, we present the cross sections and the associated spin asymmetries in terms of transverse momentum dependent parton distribution functions (TMDs) at tree level within the TMD factorization formalism. To assess the feasibility of experimental measurements, we estimate the spin asymmetries for $W^{\pm }/Z^0$ boson production in polarized proton-proton collisions at the Relativistic Heavy Ion Collider by using current knowledge of the relevant TMDs. We find that some of these asymmetries can be sizable if the suppression effect from TMD evolution is not too strong. The $W$ program at RHIC can, thus, test and constrain spin theory by providing unique information on the universality properties of TMDs, TMD evolution, and the nucleon structure. For example, the single transverse spin asymmetries could be used to probe the well-known Sivers function $f_{1T}^{\perp q}$, as well as the transversal helicity distribution $g_{1T}^q$ via the parity-violating nature of $W$ production.

We study the role of the nonperturbative input to the transverse momentum dependent (TMD) gluon density in hard processes at the LHC. We derive the input TMD gluon distribution at a low scale ${\mu }_0^2\sim 1{\mathrm{GeV}}^2$ from a fit of inclusive hadron spectra measured at low transverse momenta in $pp$ collisions at the LHC and demonstrate that the best description of these spectra for larger hadron transverse momenta can be achieved by matching the derived TMD gluon distribution with the exact solution of the Balitsky-Fadin-Kuraev-Lipatov equation obtained at low $x$ and small gluon transverse momenta outside the saturation region. Then, we extend the input TMD gluon density to higher ${\mu }^2$ numerically using the Catani-Ciafoloni-Fiorani-Marchesini gluon evolution equation. Special attention is paid to phenomenological applications of the obtained TMD gluon density to some LHC processes, which are sensitive to the gluon content of a proton.

We evaluate the two-photon exchange (TPE) correction to the unpolarized elastic electron-proton scattering at small momentum transfer $Q^2$. We account for the inelastic intermediate states approximating the double virtual Compton scattering by the unpolarized forward virtual Compton scattering. The unpolarized proton structure functions are used as input for the numerical evaluation of the inelastic contribution. Our calculation reproduces the leading terms in the $Q^2$ expansion of the TPE correction and goes beyond this approximation by keeping the full $Q^2$ dependence of the proton structure functions. In the range of small momentum transfer, our result is in good agreement with the empirical TPE fit to existing data.

The breaking of parity, a fundamental symmetry between left and right, is best understood in the framework of left-right symmetric extension of the standard model. We show that the production of a heavy right-handed neutrino at the proposed Large Hadron-Electron Collider (LHeC) could give us the most simple and direct hint of the scale of this breaking in left-right symmetric theories. This production mode gives a lepton number violating signal with $\mathrm{\Delta }L=2$ which is very clean and has practically no standard model background. We highlight that the right-handed nature of $W_R$ exchange which defines the left-right symmetric theories can be confirmed by using a polarized electron beam and also enhance the production rates with relatively lower beam energy.

We carry out a systematic study of entanglement entropy in nonrelativistic conformal field theories via holographic techniques. After a discussion of recent results concerning Galilean conformal field theories, we deduce a novel expression for the entanglement entropy of ($1+1$)-dimensional Lifshitz field theories—this is done both at zero and finite temperature. Based on these results, we pose a conjecture for the anomaly coefficient of a Lifshitz field theory dual to new massive gravity. It is found that the Lifshitz entanglement entropy at finite temperature displays a striking similarity with that corresponding to a flat space cosmology in three dimensions. We claim that this structure is an inherent feature of the entanglement entropy for nonrelativistic conformal field theories. We finish by exploring the behavior of the mutual information for such theories.

We develop the perturbation theory of double field theory around arbitrary solutions of its field equations. The exact gauge transformations are written in a manifestly background covariant way and contain at most quadratic terms in the field fluctuations. We expand the generalized curvature scalar to cubic order in fluctuations and thereby determine the cubic action in a manifestly background covariant form. As a first application we specialize this theory to group manifold backgrounds, such as $SU(2)\simeq S^3$ with $H$-flux. In the full string theory this corresponds to a Wess-Zumino-Witten background CFT. Starting from closed string field theory, the cubic action around such backgrounds has been computed before by Blumenhagen, Hassler, and Lüst. We establish precise agreement with the cubic action derived from double field theory. This result confirms that double field theory is applicable to arbitrary curved background solutions, disproving assertions in the literature to the contrary.