We study the collision of two particles in the Teo wormhole spacetime, in which the wormhole is stationary and axisymmetric. We show that a nonrotating Teo wormhole cannot be a high energy particle collider, while a rotating Teo wormhole can be used to accelerate particles and create high energy collisions because of the deep effective potential of the colliding particles. The process is different from that in the vicinity of a near-extremal black hole, since here there is no event horizon. This is the first example of particle collision with high center-of-mass energy in a spacetime with no event horizon and no naked singularity and not being extremal in a clear sense. The process can unlikely have direct implications for astrophysical observations, but it is interesting as a tool to investigate wormhole instabilities.

We study the effect of coarse graining the dynamics of a pressureless self-gravitating fluid (coarse-grained dust) in the context of cosmological perturbation theory, in both the Eulerian and Lagrangian frameworks. We obtain recursion relations for the Eulerian perturbation kernels of the coarse-grained dust model by relating them to those of the standard pressureless fluid model. The effect of the coarse graining is illustrated by means of power and cross spectra for the density and velocity, which are computed up to one-loop order. In particular, the large-scale vorticity power spectrum that arises naturally from a mass-weighted velocity is derived from first principles. We find qualitatively good agreement for the magnitude, shape, and spectral index of the vorticity power spectrum with recent measurements from $N$-body simulations and results from the effective field theory of large-scale structure. To lay the ground for applications in the context of Lagrangian perturbation theory, we finally describe how the kernels obtained in Eulerian space can be mapped to Lagrangian ones.

It is well known that there is a black hole and cosmological horizons in a Kerr–de Sitter spacetime. The thermodynamic quantities on both horizons satisfy the laws of black hole thermodynamics. In this paper, by considering the relations between the two horizons, we give the effective thermodynamic quantities in axially symmetric de Sitter spacetime. The thermodynamic properties of these effective quantities are analyzed. Moreover, the critical temperature and the critical pressure are obtained. We conclude that the phase transition point is irrelevant to the angular momentum. It only depends on the ratio of the black hole horizon and the cosmological horizon. This result is consistent with the nature of the liquid-gas phase transition at the critical point and, thus, deepens the understanding of the analogy of the rotating de Sitter spacetime and liquid-gas systems.

Motivated by the gravity-fluid correspondence, we introduce a new method for characterizing nonlinear gravitational interactions. Namely we map the nonlinear perturbative form of the Einstein equation to the equations of motion of a collection of nonlinearly coupled harmonic oscillators. These oscillators correspond to the quasinormal or normal modes of the background spacetime. We demonstrate the mechanics and the utility of this formalism within the context of perturbed asymptotically anti–de Sitter black brane spacetimes. We confirm in this case that the boundary fluid dynamics are equivalent to those of the hydrodynamic quasinormal modes of the bulk spacetime. We expect this formalism to remain valid in more general spacetimes, including those without a fluid dual. In other words, although born out of the gravity-fluid correspondence, the formalism is fully independent and it has a much wider range of applicability. In particular, as this formalism inspires an especially transparent physical intuition, we expect its introduction to simplify the often highly technical analytical exploration of nonlinear gravitational dynamics.

We quantize spherically symmetric electrovacuum gravity. The algebra of Hamiltonian constraints can be made Abelian via a rescaling and linear combination with the diffeomorphism constraint. As a result the constraint algebra is a true Lie algebra. We complete the Dirac quantization procedure using loop quantum gravity techniques. We present explicitly the exact solutions of the physical Hilbert space annihilated by all constraints. The resulting quantum spacetimes resolve the singularity present in the classical theory inside charged black holes and allows us to extend the spacetime through where the singularity used to be into new regions. We argue that quantum discreteness of spacetime may also play a role in stabilizing the Cauchy horizons, though backreaction calculations are needed to confirm this point.

Direct searches for low-mass dark matter particles via scattering off target nuclei require detection of recoiling atoms with energies of $\sim 1\mathrm{keV}$ or less. The amount of electronic excitation produced by such atoms is quenched relative to a recoiling electron of the same energy. The Lindhard model of this quenching, as originally formulated, remains widely used after more than 50 years. The present work shows that for very small energies, a simplifying approximation of that model must be removed. This leads to a kinematic cutoff in the production of electronic excitation. Implications for the sensitivity of direct detection experiments are discussed.

We show that the observed rotation curves of spiral galaxies constrain the sound speed of the dark matter to be $c_s<10^{-4}c$, where $c$ is the speed of light in vacuum. Using the modified Chaplygin gas as a representative example of a class of unified dark energy models incorporating an effective dark matter component with a nonzero sound speed, we determine the most stringent constraint to date on the value of the constant contribution to the equation of state parameter in this class of models. Finally, we explain the reason why previous constraints using the cosmic microwave background and baryonic acoustic oscillations were not as competitive as the one presented in this paper and discuss the limitations of the recently proposed extended Chaplygin gas.

In the presence of a light weakly interacting massive particle (WIMP) with mass $m_{\chi }\lesssim 30\mathrm{MeV}$, there are degeneracies among the nature of the WIMP (fermion or boson), its couplings to the standard model particles (to electrons, positrons, and photons, or only to neutrinos), its mass $m_{\chi }$, and the number of equivalent (additional) neutrinos, $\mathrm{\Delta }{\mathrm{N}}_{\nu }$. These degeneracies cannot be broken by the cosmic microwave background (CMB) constraint on the effective number of neutrinos, ${\mathrm{N}}_{\text{eff}}$. However, since big bang nucleosynthesis (BBN) is also affected by the presence of a light WIMP and equivalent neutrinos, complementary BBN and CMB constraints can help to break some of these degeneracies. In a previous paper [K. M. Nollett and G. Steigman, Phys. Rev. D 89, 083508 (2014)] the combined BBN and Planck [P. A. R. Ade et al. (Planck Collaboration), Astron. Astrophys. 571, A16 (2014)] CMB constraints were used to explore the allowed ranges for $m_{\chi }$, $\mathrm{\Delta }{\mathrm{N}}_{\nu }$, and ${\mathrm{N}}_{\text{eff}}$ in the case where the light WIMPs annihilate electromagnetically (EM) to photons and/or $e^{\pm }$ pairs. In this paper the BBN predictions for the primordial abundances of deuterium and ${}^4\mathrm{He}$ (along with ${}^3\mathrm{He}$ and ${}^7\mathrm{Li}$) in the presence of a light WIMP that only couples (annihilates) to neutrinos [either standard model (SM) only or both SM and equivalent] are calculated. Recent observational estimates of the relic abundances of D and ${}^4\mathrm{He}$ are used to limit the light WIMP mass, the number of equivalent neutrinos, the effective number of neutrinos, and the present Universe baryon density (${\mathrm{\Omega }}_{\mathrm{B}}{h}^2$). Allowing for a neutrino coupled light WIMP and $\mathrm{\Delta }{\mathrm{N}}_{\nu }$ equivalent neutrinos, the combined BBN and CMB data provide lower limits to the WIMP mass that depend very little on the nature of the WIMP (Majorana or Dirac fermion, real or complex scalar boson), with a best fit $m_{\chi }\gtrsim 35\mathrm{MeV}$, equivalent to no light WIMP at all. The analysis here excludes all neutrino coupled WIMPs with masses below a few MeV, with specific limits varying from 4 to 9 MeV depending on the nature of the WIMP. In the absence of a light WIMP (either EM or neutrino coupled), BBN alone prefers $\mathrm{\Delta }{\mathrm{N}}_{\nu }=0.50\pm 0.23$, favoring neither the absence of equivalent neutrinos ($\mathrm{\Delta }{\mathrm{N}}_{\nu }=0$), nor the presence of a fully thermalized sterile neutrino ($\mathrm{\Delta }{\mathrm{N}}_{\nu }=1$). This result is consistent with the CMB constraint, ${\mathrm{N}}_{\text{eff}}=3.30\pm 0.27$ [1], constraining “new physics” between BBN and recombination. Combining the BBN and CMB constraints gives $\mathrm{\Delta }{\mathrm{N}}_{\nu }=0.35\pm 0.16$ and ${\mathrm{N}}_{\text{eff}}=3.40\pm 0.16$. As a result, while BBN and the CMB combined require $\mathrm{\Delta }{\mathrm{N}}_{\nu }\ge 0$ at $\sim 98\%$ confidence, they disfavor $\mathrm{\Delta }{\mathrm{N}}_{\nu }\ge 1$ at $>99\%$ confidence. Adding the possibility of a neutrino-coupled light WIMP extends the allowed range slightly downward for $\mathrm{\Delta }{\mathrm{N}}_{\nu }$ and slightly upward for ${\mathrm{N}}_{\text{eff}}$ simultaneously, while leaving the best-fit values unchanged.

We show that the baryon–dark-matter coincidence problem can be solved in the constrained minimal supersymmetric model. Baryons and dark matter are generated simultaneously through the late-time decay of nontopological solitons, Q-balls, which are formed after the Affleck-Dine baryogenesis. A certain relation between the universal scalar mass $m_0$ and the universal gaugino mass $M_{1/2}$ is required to solve the coincidence problem, marginally depending on the other parameters, and the result can be consistent with the observation of the 126-GeV Higgs boson. We also investigate the detectability in dark-matter direct-search experiments.

In warped 5D models of hierarchy and flavor, the first Kaluza-Klein (KK) state of the graviton $G_1$ is heavy enough to decay into a photon and its first KK mode ${\gamma }_1$ on-shell: $G_1\to {\gamma }_1\gamma$. The volume-suppression of the rate for this process [relative to 2-body decay into heavy Standard Model (SM) final states ($W/Z/t/H$)] may be partially compensated by the simplicity of the photon final state. We consider ${\gamma }_1\to W^{+}{W}^{-}$, with a typical $\mathcal{O}(1)$ branching fraction, and focus on the semileptonic final state $W(\to jj)W(\to \ell ,\nu )$ with $\ell =e,\mu$. The SM background originates from $2\to 3$ parton processes and is relatively suppressed compared to those for 2-body decays of $G_1$. Moreover, to further reduce the background, we can impose an invariant mass window cut for ${\gamma }_1$ (in addition to that for $G_1$) in this new channel. We emphasize that this “photon cascade" decay probes a different combination of (bulk and brane) interactions of the KK states than the decays into two heavy SM states. Thus, in combination with other channels, the cascade decay could be used to extract the individual underlying geometric parameters. The $3\sigma$ reach for $G_1$ in our channel is up to 1.5 TeV at the high luminosity (14 TeV) LHC, and can be extended to about 4 TeV, at $5\sigma$, at a future 100 TeV hadron collider. Along the way, we point out the novel feature that the invariant mass distribution of KK graviton decay products becomes skewed from the Breit-Wigner form, due to the KK graviton coupling growing with energy.

We use the local hidden gauge approach in order to study the $B{\overline{B}}^{*}$ and $B^{*}{\overline{B}}^{*}$ interactions for isospin $I=1$. We show that both interactions via one light meson exchange are not allowed by the Okubo-Zweig-Iizuka rule and, for that reason, we calculate the contributions due to the exchange of two pions, interacting and noninteracting among themselves, and also due to the heavy vector mesons. Then, to compare all these contributions, we use the potential related to the heavy vector exchange as an effective potential corrected by a factor which takes into account the contribution of the other light meson exchanges. In order to look for poles, this effective potential is used as the kernel of the Bethe-Salpeter equation. As a result, for the $B{\overline{B}}^{*}$ interaction we find a loosely bound state with mass in the range 10587–10601 MeV, very close to the experimental value of the $Z_b(10610)$ reported by the Belle Collaboration. For the $B^{*}{\overline{B}}^{*}$ case, we find a cusp at 10650 MeV for all spin $J=0,1,2$ cases.

The topological structure of lattice gluodynamics is studied at intermediate resolution scale in the deconfining phase with the help of a cluster analysis. UV-filtered topological charge densities are determined from a fixed number of low-lying eigenmodes of the overlap Dirac operator with three types of temporal boundary conditions applied to the valence quark fields. This method usually allows us to find all three distinguished (anti)dyon constituents in the gauge field of Kraan–van Baal–Lee–Lu (anti)caloron solutions. The clustering of the three topological charge densities in Monte Carlo generated configurations is then used to mark the positions of anticipated (anti)dyons of the corresponding type. In order to support this interpretation, inside these clusters, we search also for timelike Abelian monopole currents (defined in the maximally Abelian gauge) as well as for local holonomies with at least two approximately degenerated eigenvalues. Our results support the view that light dyon-antidyon pairs—in contrast to the heavy (anti)caloron dyon constituents—contribute dominantly to thermal Yang-Mills fields in the deconfinement phase.

The ability for most hadrons to decay via strong interactions prevents the direct measurement of their electromagnetic properties. However, a detailed understanding of how these resonant states feature in scattering processes can allow one to disentangle such information from photo production processes. In particular, there has been increasing interest in the determination of magnetic dipole moments using such methods. In a recent study [1], Gudiño et al. provide the first experimental determination of the magnetic dipole moment of the rho meson. To facilitate a comparison with this experimental determination, we present a calculation of the rho meson and pion electromagnetic form factors calculated in the framework of lattice QCD. Using the PACS-CS $2+1$ flavor full QCD gauge field configurations, we are able to access low $Q^2$ values at near-physical quark masses. Through the use of variational techniques, we control excited state systematics in the matrix elements of the lowest-lying states and gain access to the matrix elements of the first excited state. Our determination of the rho meson $g$-factor $g_{\rho }=2.21(8)$ is in excellent agreement with this experimental determination, but with a significantly smaller uncertainty.

We present new results for the amplitude $A_2$ for a kaon to decay into two pions with isospin $I=2$: $\mathrm{Re}{A}_2=1.50(4{)}_{\text{stat}}(14{)}_{\text{syst}}\times {10}^{-8}\mathrm{GeV}$; $\mathrm{Im}{A}_2=-6.99(20{)}_{\text{stat}}(84{)}_{\text{syst}}\times {10}^{-13}\mathrm{GeV}$. These results were obtained from two ensembles generated at physical quark masses (in the isospin limit) with inverse lattice spacings $a^{-1}=1.728(4)\mathrm{GeV}$ and 2.358(7) GeV. We are therefore able to perform a continuum extrapolation and hence largely to remove the dominant systematic uncertainty from our earlier results [1,2], that due to lattice artifacts. The only previous lattice computation of $K\to \pi \pi$ decays at physical kinematics was performed using an ensemble at a single, rather coarse, value of the lattice spacing [$a^{-1}\simeq 1.37(1)\mathrm{GeV}$]. We confirm the observation reported in [3] that there is a significant cancellation between the two dominant contributions to $\mathrm{Re}{A}_2$ which we suggest is an important ingredient in understanding the $\mathrm{\Delta }I=1/2$ rule, $\mathrm{Re}{A}_0/\mathrm{Re}{A}_2\simeq 22.5$, where the subscript denotes the total isospin of the two-pion final state. Our result for $A_2$ implies that the electroweak penguin contribution to ${\epsilon }^{\prime }/\epsilon$ is $\mathrm{Re}({\epsilon }^{\prime }/\epsilon {)}_{\mathrm{EWP}}=-(6.6\pm 1.0)\times {10}^{-4}$.

In this paper we explore the chiral phase transition in QCD within the three-flavor Nambu-Jona-Lasinio model with a negative coupling constant in the isoscalar axial-vector channel, which is associated with a polarized instanton–anti-instanton molecule background. The QCD phase diagram described in this scenario shows a new first order phase transition around the transition temperature $T_c$ toward a phase without chiral condensates, but with nontrivial dynamic chiral chemical potentials for the light quarks, spontaneously giving rise to local charge parity violation and local chirality imbalance. The corresponding critical temperature $T_{5c}$ for this phase transition decreases with the magnetic field and it gives a natural explanation to the inverse magnetic catalysis effect for light quarks when incorporating a reasonable value of the coupling constant in the isoscalar axial-vector channel. Furthermore, when the isoscalar axial-vector interaction is dominant in the light quark sector and suppressed in the strange quark sector, it is found that there is no inverse magnetic catalysis for strange quark condensate, which agrees with lattice results.

We investigate the electrical conductivity of dense quark matter in the vicinity of the phase transition line. We show that (i) at high density Drude conductivity does not depend on the magnetic field up to $eB\sim 10^{19}G$, and (ii) in the precritical region, the fluctuation electrical conductivity (paraconductivity) dominates over the Drude one.

We study the transverse momentum dependent (TMD) parton distributions in the newly proposed quasiparton distribution function framework in Euclidean space. In this framework, the parton distributions can be extracted from lattice observables in a systematic expansion of $1/P_z$ where $P_z$ is the hadron momentum. A soft factor subtraction is found to be essential to make the TMDs calculable on the lattice. We show that the quasi-TMDs with the associated soft factor subtraction can be applied in hard QCD scattering processes such as Drell-Yan lepton pair production in hadronic collisions. This allows future lattice calculations to provide information on the nonperturbative inputs and energy evolutions for the TMDs. Extension to the generalized parton distributions and quantum phase space Wigner distributions will lead to a complete nucleon tomography on the lattice.

We investigate the factorization hypothesis of the four-quark condensate $⟨q\overline{q}q\overline{q}⟩=A⟨q\overline{q}{⟩}^2$ by considering the Nambu–Jona-Lasinio model supplemented with sixth- and eighth-order interactions. For that purpose we use the bosonization method with multiple auxiliary variables. We find that in a simplified U(1) version of the model factorization holds, whereas in the full U(3)-flavor version of the model, factorization is broken by terms which are related to the ’t Hooft interaction.

The McLerran-Venugopalan model describes a highly boosted hadron/nucleus as a sheet of random color charges which source soft classical Weizsäcker-Williams gluon fields. We show that due to fluctuations, individual configurations are azimuthally anisotropic. We present initial evidence that impact parameter dependent small-$x$ Jalilian-Marian, Iancu, McLerran, Weigert, Leonidov and Kovner (JIMWLK) resummation preserves such anisotropies over several units of rapidity. Finally, we compute the first four azimuthal Fourier amplitudes of the S-matrix of a fundamental dipole in such background fields.

Unitary evolution law describes isolated particle scattering processes in an empty Minkowski spacetime. We put forward a hypothesis that the physical Universe includes a quantum environment that interacts with some particle scattering and decay processes. While the scattering process is governed by the $S$-matrix dynamics and its conservation laws and unitarity, the interaction with the environment evolves the produced final state ${\rho }_f(S)$ to the observed state ${\rho }_f(O)$. To be consistent with the Standard Model this new interaction must be a pure dephasing interaction. Governed by a nonunitary evolution law, it modifies the phases of the $S$-matrix amplitudes and can give rise to mixing of such amplitudes to form observed amplitudes. We present the first test of unitary evolution law in particle scattering. Conservation of $P$-parity in strong interactions imposes constraints on partial wave helicity and nucleon transversity amplitudes in $\pi N\to \pi \pi N$ processes. An independent set of constraints on these amplitudes is imposed by the $S$-matrix unitary evolution law. The unitary evolution evolves pure initial states into pure final states leading to 9 independent constraints on 16 components of angular intensities in $\pi N\to \pi \pi N$ processes. When expressed in terms of parity conserving transversity amplitudes, all 9 constraints are identities provided a single constraint on the transversity amplitudes holds true. The constraint implies that relative phases between transversity amplitudes of the same naturality and transversity must be 0 or $\pm \pi$. Assuming a self-consistent set of these unitary phases we use the CERN data on spin observables $R_u^0$ and $R_y^0$ to determine a unique solution for the $S$- and $P$-wave moduli below 1080 MeV. The data require ${\rho }^0(770)-f_0(980)$ mixing in the $S$-wave but this unitary solution is excluded by data on observables $R_x^0$ within at least 5 standard deviations. All previous amplitude analyses of $\pi N\to \pi \pi N$ processes found nonunitary relative phases in an apparent violation of the unitary evolution law. The contrast between the predicted unitary relative phases and the observed nonunitary phases presents unambiguous evidence for the nonunitary evolution of the produced final state and supports the hypothesis of the existence of a quantum environment and its pure dephasing interaction with particle scattering processes.