We present the spectrum of baryons in $SU(4)$ gauge theory with fundamental fermion constituents, which is of significant interest for composite dark matter model building. We first compare the spectra and properties of baryons in $SU(3)$ and $SU(4)$ gauge theories (in which they are fermionic and bosonic, respectively) and then compute the cross section for direct detection of dark matter via Higgs boson exchange for TeV-scale composite dark matter arising from a confining $SU(4)$ gauge sector. Comparison with the latest LUX results leads to tight bounds on the fraction of the mass of the constituent fermion that may arise from electroweak symmetry breaking. Lattice calculations of the dark matter mass spectrum and the Higgs–dark-matter coupling are performed on quenched ${16}^3\times 32$, ${32}^3\times 64$, ${48}^3\times 96$, and ${64}^3\times 128$ lattices with three different lattice spacings, using Wilson fermions with moderate to large pseudoscalar meson masses. Our results lay a foundation for future analytic and numerical studies of composite baryonic dark matter.

In the framework of the one-boson exchange model, we have calculated the effective potentials between two heavy mesons $B{\overline{B}}^{*}$ and $D{\overline{D}}^{*}$ from the t- and u-channel $\pi$-, $\eta$-, $\rho$-, $\omega$-, and $\sigma$-meson exchanges with four kinds of quantum number: $I=0$, $J^{PC}=1^{++}$; $I=0$, $J^{PC}=1^{+-}$; $I=1$, $J^{PC}=1^{++}$; $I=1$, $J^{PC}=1^{+-}$. We keep the recoil corrections to the $B{\overline{B}}^{*}$ and $D{\overline{D}}^{*}$ systems up to $O(\frac{1}{M^2})$. The spin-orbit force appears at $O(\frac{1}{M})$, which turns out to be important for the very loosely bound molecular states. Our numerical results show that the momentum-related corrections are unfavorable to the formation of the molecular states in the $I=0$, $J^{PC}=1^{++}$ and $I=1$, $J^{PC}=1^{+-}$ channels in the $D{\overline{D}}^{*}$ system.

We study the signatures at the LHC of the electroweak SU(2) lepton doublet which embeds a doubly charged lepton. The doubly charged lepton pair and single production rates, which are different from the triplet case, are studied and all the detectable decay modes are considered. We also apply the same kinematic cuts as in the triplet case to reduce the background at the LHC, and the needed integrated luminosities to find the doubly charged leptons with different masses are analyzed. We also suggest a method to distinguish the exotic lepton doublet and triplet.

Whether the anarchical ansatz or more symmetric structures best describe the neutrino parameters is a long standing question that underwent a revival of interest after the discovery of a nonvanishing reactor angle and the indication of a nonmaximal atmospheric angle. In this letter, a Bayesian statistical approach is adopted in order to analyze and compare the two hypotheses within the context of $U(1)$ flavor models. We study the constraints on individual model parameters and perform a model comparison: the results elect constructions with built-in hierarchies among the matrix elements as preferred over the anarchical ones, with values of the evidence that depend slightly on whether the $U(1)$ charges are also considered free parameters or not, and on the priors used.

We perform a comprehensive study of the $\mathrm{\Delta }(96)$ family symmetry combined with the generalized $CP$ symmetry $H_{CP}$. We investigate the lepton mixing parameters which can be obtained from the original symmetry $\mathrm{\Delta }(96)⋊H_{CP}$ breaking to different remnant symmetries in the neutrino and charged lepton sectors, namely $G_{\nu }$ and $G_l$ subgroups in the neutrino and the charged lepton sector, respectively, and the remnant $CP$ symmetries from the breaking of $H_{CP}$ are $H_{CP}^{\nu }$ and $H_{CP}^l$, respectively, where all cases correspond to a preserved symmetry smaller than the full Klein symmetry, as in the semidirect approach, leading to predictions which depend on a single undetermined real parameter, which may be fitted to the reactor angle for example. We discuss 26 possible cases, including a global ${\chi }^2$ determination of the best fit parameters and the correlations between mixing parameters, in each case.

Measurements of the differential cross sections for the production of exactly four jets in proton-proton collisions are presented as a function of the transverse momentum $p_{\mathrm{T}}$ and pseudorapidity $\eta$, together with the correlations in azimuthal angle and the $p_{\mathrm{T}}$ balance among the jets. The data sample was collected in 2010 at a center-of-mass energy of 7 TeV with the CMS detector at the LHC, with an integrated luminosity of $36{\mathrm{pb}}^{-1}$. The cross section for exactly four jets, with two hard jets of $p_{\mathrm{T}}>50\mathrm{GeV}$ each, together with two jets of $p_{\mathrm{T}}>20\mathrm{GeV}$ each, within $|\eta |<4.7$ is measured to be $\sigma =330\pm 5\text{(stat.)}\pm 45(\text{syst.})\mathrm{nb}$. It is found that fixed-order matrix element calculations including parton showers describe the measured differential cross sections in some regions of phase space only, and that adding contributions from double parton scattering brings the Monte Carlo predictions closer to the data.

We consider the finite temperature effective potential of the standard model at the one-loop level in four dimensions by taking account of two kinds of order parameters, the Higgs vacuum expectation value and the zero modes of gauge fields for the Euclidean time direction. We study the vacuum structure of the model, focusing on the existence of the new phase, where the zero modes, that is, the new order parameters, develop nontrivial vacuum expectation values except for the center of the gauge group. We find that under certain conditions there appears no new phase at finite temperature.

Quantum Hall effects on the complex Grassmann manifolds ${\mathbf{Gr}}_2({\mathbb{C}}^N)$ are formulated. We set up the Landau problem in ${\mathbf{Gr}}_2({\mathbb{C}}^N)$ and solve it using group theoretical techniques and provide the energy spectrum and the eigenstates in terms of the $SU(N)$ Wigner $\mathcal{D}$ functions for charged particles on ${\mathbf{Gr}}_2({\mathbb{C}}^N)$ under the influence of Abelian and non-Abelian background magnetic monopoles or a combination of these. In particular, for the simplest case of ${\mathbf{Gr}}_2({\mathbb{C}}^4)$, we explicitly write down the $U(1)$ background gauge field as well as the single- and many-particle eigenstates by introducing the Plücker coordinates and show by calculating the two-point correlation function that the lowest Landau level at filling factor $\nu =1$ forms an incompressible fluid. Our results are in agreement with the previous results in the literature for the quantum Hall effect on $\mathbb{C}{P}^N$ and generalize them to all ${\mathbf{Gr}}_2({\mathbb{C}}^N)$ in a suitable manner. Finally, we heuristically identify a relation between the $U(1)$ Hall effect on ${\mathbf{Gr}}_2({\mathbb{C}}^4)$ and the Hall effect on the odd sphere $S^5$, which is yet to be investigated in detail, by appealing to the already-known analogous relations between the Hall effects on $\mathbb{C}{P}^3$ and $\mathbb{C}{P}^7$ and those on the spheres $S^4$ and $S^8$, respectively.

We develop a high-precision model for laser ranging interferometric (LRI) observables of the GRACE Follow-On (GRACE-FO) mission. For this, we study the propagation of an electromagnetic wave in the gravitational field in the vicinity of an extended body, in the post-Newtonian approximation of the general theory of relativity. We present a general relativistic model for the phase of a plane wave that accounts for contributions of all the multipoles of the gravitating body and its angular momentum, as well as the contribution of tidal fields produced by external sources. We develop a new approach to model a coherent signal transmission in the gravitational field of the Solar System that relies on a relativistic treatment of the phase. We use this approach to describe high-precision interferometric measurements on GRACE-FO and formulate the key LRI observables, namely, the phase and phase rate of a coherent laser link between the two spacecraft. We develop a relativistic model for the LRI-enabled range between the two GRACE-FO spacecraft, accurate to less than 1 nm, and a high-precision model for the corresponding range rate, accurate to better than 0.1 nm/s. We also formulate high-precision relativistic models for the double one-way range (DOWR) and DOWR-enabled range-rate observables originally used on GRACE and now studied for interferometric measurements on GRACE-FO. Our formulation justifies the basic assumptions behind the design of the GRACE-FO mission and highlights the importance of achieving nearly circular and nearly identical orbits for the GRACE-FO spacecraft.

We consider Dirac neutrinos interacting with background fermions in the frame of the standard model. We demonstrate that a time-dependent effective potential is quite possible in a protoneutron star (PNS) at certain stages of its evolution. For the first time, we formulate a nonperturbative treatment of neutrino processes in a matter with arbitrary time-dependent effective potential. Using linearly growing effective potential, we study the typical case of a slowly varying matter interaction potential. We calculate differential mean numbers of $\nu \overline{\nu }$ pairs created from the vacuum by this potential and find that they crucially depend on the magnitude of masses of the lightest neutrino eigenstate. These distributions uniformly span up to $\sim 10\mathrm{eV}$ energies for muon and tau neutrinos created in PNS core due to the compression just before the hydrodynamic bounce and up to $\sim 0.1\mathrm{eV}$ energies for all three active neutrino flavors created in the neutronization. Considering different stages of the PNS evolution, we derive constraints on neutrino masses, $m_{\nu }\lesssim (10^{-8}-10^{-7})\mathrm{eV}$, corresponding to the nonvanishing $\nu \overline{\nu }$ pairs flux produced by this mechanism. We show that one can distinguish such coherent flux from chaotic fluxes of any other origin. Part of these neutrinos, depending on the flavor and helicity, are bounded in the PNS, while antineutrinos of any flavor escape the PNS. If the created pairs are ${\nu }_e{\overline{\nu }}_e$, then a part of the corresponding neutrinos also escape the PNS. The detection of $\nu$ and $\overline{\nu }$ with such low energies is beyond current experimental techniques.

It was proposed by Ryu and Takayanagi that the entanglement entropy in conformal field theory (CFT) is related through the AdS/CFT correspondence to the area of a minimal surface in the bulk. We apply this holographic geometrical method of calculating the entanglement entropy to study the vacuum case of a CFT which is holographically dual to empty anti-de Sitter (AdS) spacetime. We present all possible minimal surfaces spanned on one or two spherical boundaries at AdS infinity. We give exact analytical expressions for the regularized areas of these surfaces and identify finite renormalized quantities. In the case of two disjoint boundaries the existence of two different phases of the entanglement entropy is confirmed. A trivial phase corresponds to two disconnected minimal surfaces, while the other one corresponds to a tube connecting the spherical boundaries. A transition between these phases is reminiscent of the finite temperature deconfinement transition in the CFT on the boundary. The exact analytical results are thus consistent with previous numerical and approximate computations. We also briefly discuss the character of a spacetime extension of the minimal surface spanned on two uniformly accelerated boundaries.

Spinning black holes tend to expel magnetic fields. In this way they are similar to superconductors. It has been a persistent concern that this black hole “Meissner effect” could quench jet power at high spins. This would make it impossible for the rapidly rotating black holes in Cyg X-1 and GRS $1915+105$ to drive Blandford-Znajek jets. We give a simple geometrical argument why fields which become entirely radial near the horizon are not expelled by the Meissner effect and may continue to power jets up to the extremal limit. A simple and natural example is a split-monopole field. We stress that ordinary Blandford-Znajek jets are impossible if the Meissner effect operates and expels the field. Finally, we note that in our general relativistic magnetohydrodynamic simulations of black hole jets, there is no evidence that jets are quenched by the Meissner effect. The simulated jets develop a large split-monopole component spontaneously which supports our proposal for how the Meissner effect is evaded and jets from rapidly rotating black holes are powered in nature.

This paper deals with a special kind of problems that appear in solutions of Einstein’s field equations for extended bodies: many structure-dependent terms appear in intermediate calculations that cancel exactly in virtue of the local equations of motion or can be eliminated by appropriate gauge transformations. For a single body at rest, these problems are well understood for both the post-Newtonian and the post-Minkowskian cases. However, the situation is still unclear for approximations of higher orders. This paper discusses this problem for a “body” of spherical symmetry to post-linear order. We explicitly demonstrate how the usual Schwarzschild field can be derived directly from the field equations in the post-linear approximation in the harmonic gauge and for an arbitrary spherically symmetric matter distribution. Both external and internal solutions are considered. The case of static incompressible fluid is then compared to the well-known results from the literature. The results of this paper can be applied to generalize the well-known post-Newtonian and post-Minkowskian multipole expansions of the metric in the post-linear approximation.

The equations of motion for spinning compact binaries on eccentric orbits are treated perturbatively in powers of a fractional mass-difference ordering parameter. The solution is valid through first order in the mass-difference parameter. A canonical point transformation removes the leading-order terms of the spin-orbit Hamiltonian which induce a wiggling precession of the orbital angular momentum around the conserved total angular momentum, a precession which disappears in the case of equal masses or one single spin. Action-angle variables are applied that make a canonical perturbation theory easily treatable.

We investigate the properties of relativistic star spheres made of an electrically charged incompressible fluid, generalizing, thus, the Schwarzschild interior solution. The investigation is carried by integrating numerically the hydrostatic equilibrium equation, i.e., the Tolman-Oppenheimer-Volkoff (TOV) equation, with the hypothesis that the charge distribution is proportional to the energy density. We match the interior to a Reissner-Nordström exterior, and study some features of these star spheres such as the total mass $M$, the radius $R$, and the total charge $Q$. We also display the pressure profile. For star spheres made of a perfect fluid there is the Buchdahl bound, $R/M\ge 9/4$, a compactness bound found from generic principles. For the Schwarzschild interior solution there is also the known compactness limit, the interior Schwarzschild limit where the configurations attain infinite central pressure, given by $R/M=9/4$, yielding an instance where the Buchdahl bound is saturated. We study this limit of infinite central pressure for the electrically charged stars and compare it with the Buchdahl-Andréasson bound, a limit that, like the Buchdahl bound for the uncharged case, is obtained by imposing some generic physical conditions on charged configurations. We show that the electrical interior Schwarzschild limit of all but two configurations is always below the Buchdahl-Andréasson limit, i.e., we find that the electrical interior Schwarzschild limit does not generically saturate the Buchdahl-Andréasson bound. We also find that the quasiblack hole limit, i.e., the extremal most compact limit for charged incompressible stars, is reached when the matter is highly charged and the star’s central pressure tends to infinity. This is one of the two instances where the Buchdahl-Andréasson bound is saturated, the other being the uncharged, interior Schwarzschild solution.

We calculate the absorption cross section of a massive neutral scalar field impinging upon a Reissner-Nordström black hole. First, we derive key approximations in the high- and low-frequency regimes. Next, we develop a numerical method to compute the cross section at intermediate frequencies, and present a selection of results. Finally, we draw together our complementary approaches to give a quantitative full-spectrum description of absorption.

Magnetic fields surrounding spinning black holes can confine radiation and trigger superradiant instabilities. To investigate this effect, we perform the first fully-consistent linear analysis of the Ernst spacetime, an exact solution of the Einstein–Maxwell equations describing a black hole immersed in a uniform magnetic field $B$. In the limit in which the black-hole mass vanishes, the background reduces to the marginally stable Melvin spacetime. The presence of an event horizon introduces a small dissipative term, resulting in a set of long-lived—or unstable—modes. We provide a simple interpretation of the mode spectrum in terms of a small perfect absorber immersed in a confining box of size $\sim 1/B$ and show that rotation triggers a superradiant instability. By studying scalar perturbations of a magnetized Kerr–Newman black hole, we are able to confirm and quantify the details of this instability. The instability time scale can be orders of magnitude shorter than that associated to massive bosonic fields. The instability extracts angular momentum from the event horizon, competing against accretion. This implies that strong magnetic fields set an upper bound on the black-hole spin. Conversely, observations of highly-spinning massive black holes impose an intrinsic limit to the strength of the surrounding magnetic field. We discuss the astrophysical implications of our results and the limitations of the Ernst spacetime to describe realistic astrophysical configurations.

We present a lower bound for the multifield bounce action with a quartic potential with bounded coefficients in the absence of gravity. We find that for a large number of fields the lower bound decreases with the number of fields as $N^{-3}$. This work clarifies previous statements made in numerical studies which found that the bounce action scales as $N^{-2.66}$ and discusses some subtleties of studying field space trajectories.

Bulk motions of electrons along the line of sight induce secondary temperature fluctuations in the postdecoupling, reionized Universe. In the presence of a magnetic field not only the scalar mode but also the vector mode act as a source for the bulk motion. The resulting angular power spectrum of temperature anisotropies of the cosmic microwave background is calculated assuming a simple model of reionization. Contributions from the standard adiabatic, curvature mode and a nonhelical magnetic field are included. The contribution due to magnetic fields with field strengths of order nG and negative magnetic spectral indices becomes important for multipoles larger than $\ell \sim {10}^4$.

The crystalline color superconducting phase is believed to be the ground state of deconfined quark matter for sufficiently large values of the strange quark mass. This phase has the remarkable property of being more rigid than any known material. It can therefore sustain large shear stresses, supporting torsional oscillations of large amplitude. The torsional oscillations could lead to observable electromagnetic signals if strange stars have a crystalline color superconducting crust. Indeed, considering a simple model of a strange star with a bare quark matter surface, it turns out that a positive charge is localized in a narrow shell about ten Fermi thick beneath the star surface. The electrons needed to neutralize the positive charge of quarks spill in the star exterior forming an electromagnetically bounded atmosphere hundreds of Fermi thick. When a torsional oscillation is excited, for example by a stellar glitch, the positive charge oscillates with typical kHz frequencies, for a crust thickness of about one-tenth of the stellar radius, to hundreds of Hz, for a crust thickness of about nine-tenths of the stellar radius. Higher frequencies, of the order of few GHz, can be reached if the star crust is of the order of a few centimeters thick. We estimate the emitted power considering emission by an oscillating magnetic dipole, finding that it can be quite large, of the order of ${10}^{45}\mathrm{erg}/\mathrm{s}$ for a thin crust. The associated relaxation times are very uncertain, with values ranging between microseconds and minutes, depending on the crust thickness. The radiated photons will be in part absorbed by the electronic atmosphere, but a sizable fraction of them should be emitted by the star.