The installation of forward detectors in CMS and ATLAS turn the LHC into an effective photon-photon collider. The elastic scattering of the beam protons via the emission of photons, which can be identified by tagging the intact protons in the forward detectors, provides a powerful diagnostic of the central production of new particles through photon-photon annihilation. In this paper we study the central production of dark matter particles and the potential of the LHC to constrain the cross section of this process. By virtue of the crossing symmetry, this limit can immediately be used to constrain the production of monochromatic gamma rays in dark matter annihilation, a smoking gun signal under investigation in indirect dark matter searches. We show that with the integrated luminosity $\mathcal{L}=30{\mathrm{fb}}^{-1}$ in the LHC at center-of-mass energy $\sqrt{s}=13\mathrm{TeV}$, for dark matter masses $\sim (50–600)\mathrm{GeV}$, a model-independent constraint on the cross section of dark matter annihilation to monochromatic gamma rays at the same order of magnitude as the current Fermi-LAT and the future limits from CTA can be obtained.

According to the ideal walking technicolor paradigm, large mass anomalous dimensions arise in gauged Nambu–Jona-Lasinio (NJL) models when the four-fermion coupling is sufficiently strong to induce spontaneous symmetry breaking in an otherwise conformal gauge theory. We therefore study the $SU(2)$ gauged NJL model with two adjoint fermions using lattice simulations. The model is in an infrared conformal phase at small NJL coupling while it displays a chirally broken phase at large NJL couplings. In the infrared conformal phase, we find that the mass anomalous dimension varies with the NJL coupling, reaching ${\gamma }_m\sim 1$ close to the chiral symmetry breaking transition, de facto making the present model the first explicit realization of the ideal walking scenario.

We present a precise lattice computation of pseudoscalar and vector heavy-light meson masses for heavy-quark masses ranging from the physical charm mass up to $\simeq 4$ times the physical $b$-quark mass. We employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with $N_f=2+1+1$ dynamical quarks at three values of the lattice spacing ($a\simeq 0.062,0.082,0.089\mathrm{fm}$) with pion masses in the range $M_{\pi }\simeq 210–450\mathrm{MeV}$. The heavy-quark mass is simulated directly on the lattice up to $\simeq 3$ times the physical charm mass. The interpolation to the physical $b$-quark mass is performed using the ETMC ratio method, based on ratios of the meson masses computed at nearby heavy-quark masses, and adopting the kinetic mass scheme. The extrapolation to the physical pion mass and to the continuum limit yields $m_b^{\mathrm{kin}}(1\mathrm{GeV})=4.61(20)\mathrm{GeV}$, which corresponds to ${\overline{m}}_b({\overline{m}}_b)=4.26(18)\mathrm{GeV}$ in the $\overline{\mathrm{MS}}$ scheme. The lattice data are analyzed in terms of the heavy-quark expansion (HQE) and the matrix elements of dimension-four and dimension-five operators are extracted with a good precision, namely, $\overline{\mathrm{\Lambda }}=0.552(26)\mathrm{GeV}$, ${\mu }_{\pi }^2=0.321(32){\mathrm{GeV}}^2$, and ${\mu }_G^2(m_b)=0.253(25){\mathrm{GeV}}^2$. The data also allow for a rough estimate of the dimension-six operator matrix elements. As the HQE parameters play a crucial role in the inclusive determination of the Cabibbo-Kobayashi-Maskawa matrix elements $V_{ub}$ and $V_{cb}$, their precise determination on the lattice may eventually validate and improve the analyses based on fits to the semileptonic moments.

We study the Polyakov loop correlator in the weak coupling expansion and show how the perturbative series reexponentiates into singlet and adjoint contributions. We calculate the order $g^7$ correction to the Polyakov loop correlator in the short distance limit. We show how the singlet and adjoint free energies arising from the reexponentiation formula of the Polyakov loop correlator are related to the gauge invariant singlet and octet free energies that can be defined in pNRQCD, namely we find that the two definitions agree at leading order in the multipole expansion, but differ at first order in the quark-antiquark distance.

We study the charmed and bottomed doubly strange baryons within the heavy-quark-light-diquark framework. The two strange quarks are assumed to lie in $S$ wave and thus their total spin is 1. We calculate the mass spectra of the $S$- and $P$-wave orbitally excited states and find the ${\mathrm{\Omega }}_c^0(2695)$ and ${\mathrm{\Omega }}_c^0(2770)$ fit well as the $S$-wave states of charmed doubly strange baryons. The five newly ${\mathrm{\Omega }}_c^0(X)$ resonances observed by the LHCb Collaboration, i.e., ${\mathrm{\Omega }}_c^0(3000)$, ${\mathrm{\Omega }}_c^0(3050)$, ${\mathrm{\Omega }}_c^0(3066)$, ${\mathrm{\Omega }}_c^0(3090)$, and ${\mathrm{\Omega }}_c^0(3119)$, can be interpreted as the $P$-wave orbitally excited states. In heavy quark effective theory, we analyze their decays into the ${\mathrm{\Xi }}_c^{+}{K}^{-}$ and ${\mathrm{\Xi }}_c^{\prime +}{K}^{-}$, and point out that decays of the five P-wave ${\mathrm{\Omega }}_c^0$ states into the ${\mathrm{\Xi }}_c^{+}{K}^{-}$ and ${{\mathrm{\Xi }}_c^{\prime }}^{+}{K}^{-}$ are suppressed by either heavy quark symmetry or phase space. The narrowness of the five newly observed ${\mathrm{\Omega }}_c^0(X)$ states can then be naturally interpreted with heavy quark symmetry.

We compute photon production at early times in semicentral relativistic heavy-ion collisions from nonequilibrium gluon fusion induced by a magnetic field. The calculation accounts for the main features of the collision at these early times, namely, the intense magnetic field and the high gluon occupation number. The gluon fusion channel is made possible by the magnetic field and would otherwise be forbidden due to charge conjugation invariance. Thus, the photon yield from this process is an excess over calculations without magnetic field effects. We compare this excess to the difference between PHENIX data and recent hydrodynamic calculations for the photon transverse momentum distribution and elliptic flow coefficient $v_2$. We show that with reasonable values for the saturation scale and magnetic field strength, the calculation helps us better describe the experimental results obtained at RHIC energies for the lowest part of the transverse photon momentum.

A search is presented for supersymmetry in all-hadronic events with missing transverse momentum and tagged top quarks. The data sample was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of $2.3{\mathrm{fb}}^{-1}$ of proton-proton collisions at a center-of-mass energy of 13 TeV. Search regions are defined using the properties of reconstructed jets, the multiplicity of bottom and top quark candidates, and an imbalance in transverse momentum. With no statistically significant excess of events observed beyond the expected contributions from the standard model, we set exclusion limits at 95% confidence level on the masses of new particles in the context of simplified models of direct and gluino-mediated top squark production. For direct top squark production with decays to a top quark and a neutralino, top squark masses up to 740 GeV and neutralino masses up to 240 GeV are excluded. Gluino masses up to 1550 GeV and neutralino masses up to 900 GeV are excluded for a gluino-mediated production case, where each of the pair-produced gluinos decays to a top-antitop quark pair and a neutralino.

We investigate the structure of the three-qubit magic Veldkamp line (MVL). This mathematical notion has recently shown up as a tool for understanding the structures of the set of Mermin pentagrams, objects that are used to rule out certain classes of hidden variable theories. Here we show that this object also provides a unifying finite geometric underpinning for understanding the structure of functionals used in form theories of gravity and black hole entropy. We clarify the representation theoretic, finite geometric and physical meaning of the different parts of our MVL. The upshot of our considerations is that the basic finite geometric objects enabling such a diversity of physical applications of the MVL are the unique generalized quadrangles with lines of size three, their one-point extensions as well as their other extensions isomorphic to affine polar spaces of rank 3 and order 2. In a previous work we have already connected generalized quadrangles to the structure of cubic Jordan algebras related to entropy fomulas of black holes and strings in five dimensions. In some respect the present paper can be regarded as a generalization of that analysis for also providing a finite geometric understanding of four-dimensional black hole entropy formulas. However, we find many more structures whose physical meaning is yet to be explored. As a familiar special case our work provides a finite geometric representation of the algebraic extension from cubic Jordan algebras to Freudenthal systems based on such algebras.

We analyze the interactions of particle detectors with coherent states of a free scalar field. We find that the eigenvalues of the postinteraction density matrices of i) a single detector, ii) two detectors, and iii) the partial transpose of the latter, are all independent of which coherent state the field was in. A consequence of these results is that a detector pair can harvest the same amount of entanglement from any coherent field state as from the vacuum.

We study the excess of (Renyi) entanglement entropy in various free field theories for the locally excited states defined by acting with local operators on the ground state. It is defined by subtracting the entropy for the ground state from the one for the excited state. Here the spacetime dimension is greater than or equal to 4. We find a correspondence between entanglement and a probability. The probability with which a quasiparticle exists in a subregion gives the excess of the entropy. We also propose a toy model which reproduces the excess in the replica method. In this model, a quasiparticle created by a local operator propagates freely and its probability distribution gives the excess.

We extend the standard construction of conserved currents for matter fields in general relativity to general gauge theories. In the original construction, the conserved current associated with a spacetime symmetry generated by a Killing field $h^{\mu }$ is given by $\sqrt{-g}{T}^{\mu \nu }{h}_{\nu }$, where $T^{\mu \nu }$ is the energy-momentum tensor of the matter. We show that if in a Lagrangian field theory that has gauge symmetry in the general Noetherian sense some of the elementary fields are fixed and are invariant under a particular infinitesimal gauge transformation, then there is a current ${\mathcal{B}}^{\mu }$ that is analogous to $\sqrt{-g}{T}^{\mu \nu }{h}_{\nu }$ and is conserved if the nonfixed fields satisfy their Euler-Lagrange equations. The conservation of ${\mathcal{B}}^{\mu }$ can be seen as a consequence of an identity that is a generalization of ${\nabla }_{\mu }{T}^{\mu \nu }=0$ and is a consequence of the gauge symmetry of the Lagrangian. This identity holds in any configuration of the fixed fields if the nonfixed fields satisfy their Euler-Lagrange equations. We also show that ${\mathcal{B}}^{\mu }$ differs from the relevant canonical Noether current by the sum of an identically conserved current and a term that vanishes if the nonfixed fields are on shell. For an example, we discuss the case of general, possibly fermionic, matter fields propagating in fixed gravitational and Yang-Mills background. We find that in this case the generalization of ${\nabla }_{\mu }{T}^{\mu \nu }=0$ is the Lorentz law ${\nabla }_{\mu }{T}^{\mu \nu }-F^{a\nu \lambda }{\mathcal{J}}_{a\lambda }=0$, which holds as a consequence of the diffeomorphism, local Lorentz and Yang-Mills gauge symmetry of the matter Lagrangian. For a second simple example, we consider the case of general fields propagating in a background that consists of a gravitational and a real scalar field.

We use quantum energy teleportation in the light-matter interaction as an operational means to create quantum field states that violate energy conditions and have negative local stress-energy densities. We show that the protocol is optimal in the sense that it scales in a way that saturates the quantum interest conjecture.

Utilizing concepts from dynamical systems theory, we demonstrate how the existence of light rings, or fixed points, in a spacetime will give rise to families of periodic orbits and invariant manifolds in phase space. It is shown that these structures can define the shape of the black hole shadow as well as a number of salient features of the spacetime lensing. We illustrate this through the analysis of lensing by a hairy black hole.

Ladder operators can be useful constructs, allowing for unique insight and intuition. In fact, they have played a special role in the development of quantum mechanics and field theory. Here, we introduce a novel type of ladder operators, which map a scalar field onto another massive scalar field. We construct such operators, in arbitrary dimensions, from closed conformal Killing vector fields, eigenvectors of the Ricci tensor. As an example, we explicitly construct these objects in anti–de Sitter ($AdS$) spacetime and show that they exist for masses above the Breitenlohner-Freedman bound. Starting from a regular seed solution of the massive Klein-Gordon equation, mass ladder operators in AdS allow one to build a variety of regular solutions with varying boundary condition at spatial infinity. We also discuss mass ladder operator in the context of spherical harmonics, and the relation between supersymmetric quantum mechanics and so-called Aretakis constants in an extremal black hole.

An important aspect in understanding the dynamics in the context of deparametrized models of loop quantum gravity (LQG) is to obtain a sufficient control on the quantum evolution generated by a given Hamiltonian operator. More specifically, we need to be able to compute the evolution of relevant physical states and observables with a relatively good precision. In this article, we introduce an approximation method to deal with the physical Hamiltonian operators in deparametrized LQG models, and we apply it to models in which a free Klein-Gordon scalar field or a nonrotational dust field is taken as the physical time variable. This method is based on using standard time-independent perturbation theory of quantum mechanics to define a perturbative expansion of the Hamiltonian operator, the small perturbation parameter being determined by the Barbero-Immirzi parameter $\beta$. This method allows us to define an approximate spectral decomposition of the Hamiltonian operators and hence to compute the evolution over a certain time interval. As a specific example, we analyze the evolution of expectation values of the volume and curvature operators starting with certain physical initial states, using both the perturbative method and a straightforward expansion of the expectation value in powers of the time variable. This work represents a first step toward achieving the goal of understanding and controlling the new dynamics developed in Alesci et al. [Phys. Rev. D 91, 124067 (2015)] and Assanioussi et al. [Phys. Rev. D 92, 044042 (2015)].

We investigate the Lorentz symmetry breaking effects (LSBE) on the deflection of light by a rotating cosmic string spacetime in the weak limit approximation. We first calculate the deflection angle by a static cosmic string for a fixed spacelike 4-vector case (FSL) with the corresponding effective-string optical metric using the Gauss-Bonnet theorem (GBT). Then, we focus on a more general scenario, namely we calculate the deflection angle by a rotating cosmic string applying the GBT to Randers effective-string metric. We obtain a significant modification in the deflection angle because of the LSBE parameter. We find first and second order correction terms due to the global effective topology which are proportional to the cosmic string and LSBE parameter, respectively. Finally, for a fixed time-like 4-vector (FTL) case, we show that the deflection angle is not affected by LSBE parameter.

The standard black holes (BHs) in general relativity, as well as other ultracompact objects (with or without an event horizon) admit planar circular photon orbits. These light rings (LRs) determine several spacetime properties. For instance, stable LRs trigger instabilities and, in spherical symmetry, (unstable) LRs completely determine BH shadows. In generic stationary, axisymmetric spacetimes, nonplanar bound photon orbits may also exist, regardless of the integrability properties of the photon motion. We suggest a classification of these fundamental photon orbits (FPOs) and, using Poincaré maps, determine a criterion for their stability. For the Kerr BH, all FPOs are unstable (similar to its LRs) and completely determine the Kerr shadow. But in non-Kerr spacetimes, stable FPOs may also exist, even when all LRs are unstable, triggering new instabilities. We illustrate this for the case of Kerr BHs with Proca hair, wherein, moreover, qualitatively novel shadows with a cuspy edge exist, a feature that can be understood from the interplay between stable and unstable FPOs. FPOs are the natural generalization of LRs beyond spherical symmetry and should generalize the LRs key role in different spacetime properties.

The absence of a true thermodynamical equilibrium for an observer located in the causal area of a Schwarzschild–de Sitter spacetime has repeatedly raised the question of the correct definition of its temperature. In this work, we consider five different temperatures for a higher-dimensional Schwarzschild–de Sitter black hole: the bare $T_0$, the normalized $T_{\mathrm{BH}}$, and three effective ones given in terms of both the black-hole and cosmological horizon temperatures. We find that these five temperatures exhibit similarities but also significant differences in their behavior as the number of extra dimensions and the value of the cosmological constant are varied. We then investigate their effect on the energy emission spectra of Hawking radiation. We demonstrate that the radiation spectra for the normalized temperature $T_{\mathrm{BH}}$—proposed by Bousso and Hawking over twenty years ago—leads to the dominant emission curve, while the other temperatures either support a significant emission rate only in a specific $\mathrm{\Lambda }$ regime or have their emission rates globally suppressed. Finally, we compute the bulk-over-brane emissivity ratio and show that the use of different temperatures may lead to different conclusions regarding the brane or bulk dominance.

Numerical results, based on a lattice method for computational general relativity, will be presented for Cauchy evolution of initial data for the Brill, Teukolsky and polarized Gowdy spacetimes. The simple objective of this paper is to demonstrate that the lattice method can, at least for these spacetimes, match results obtained from contemporary methods. Some of the issues addressed in this paper include the handling of axisymmetric instabilities (in the Brill space-time) and an implementation of a Sommerfeld radiation condition for the Brill and Teukolsky spacetimes. It will be shown that the lattice method performs particularly well in regard to the passage of the waves through the outer boundary. Questions concerning multiple black holes, mesh refinement and long term stability will not be discussed here but may form the basis of future work.

The Darboux transformation between ordinary differential equations is a 19th century technique that has seen wide use in quantum theory for producing exactly solvable potentials for the Schrödinger equation with specific spectral properties. In this paper we show that the same transformation appears in black hole theory, relating, for instance, the Zerilli and Regge-Wheeler equations for axial and polar Schwarzschild perturbations. The transformation reveals these two equations to be isospectral, a well known result whose method has been repeatedly reintroduced under different names. We highlight the key role that the so-called algebraically special solutions play in the black hole Darboux theory and show that a similar relation exists between the Chandrasekhar-Detweiler equations for Kerr perturbations. Finally, we discuss the limitations of the method when dealing with long-range potentials and explore the possibilities offered by a generalized Darboux transformation.