It has been theoretically presumed from an effective Lagrangian calculation that there may exist two charged strangeonium-like molecular states $Z_{s1}^{+}$ and $Z_{s2}^{+}$, with $K{\overline{K}}^{*}$ and $K^{*}{\overline{K}}^{*}$ configurations, respectively. In the framework of QCD sum rules, we predict that the masses of $Z_{s1}^{+}$ ($K{\overline{K}}^{*}$) and $Z_{s2}^{+}$ ($K^{*}{\overline{K}}^{*}$) are $1.85\pm 0.14\mathrm{GeV}$ and $2.02\pm 0.15\mathrm{GeV}$, respectively, which are both above their respective two meson thresholds. We suggest to put in practice the search for these two charged strangeonium-like structures in future experiments.

Partial decay widths of various decay channels of the $X(1835)$ are evaluated in the ${}^{3}P_0$ quark model, assuming that the $X(1835)$ is an $N\overline{N}$ bound state with the quantum number assignment $I^G(J^{PC})=0^{+}(0^{-+})$. It is found that the decays to the $\rho \rho$, $\omega \omega$, and $\pi a_0(1450)$ states dominate over other channels, and that the product branching fractions $\mathrm{Br}(J/\psi \to \gamma X)\mathrm{Br}(X\to \pi \pi \eta )$ and $\mathrm{Br}(J/\psi \to \gamma X)\mathrm{Br}(X\to \pi \pi {\eta }^{\prime })$ are in the same order. We suggest that the $X(1835)$ may be searched in the $\pi a_0(1450)$ channel.

We study charmed and strange baryon resonances that are generated dynamically by a unitary baryon-meson coupled-channel model which incorporates heavy-quark spin symmetry. This is accomplished by extending the SU(3) Weinberg-Tomozawa chiral Lagrangian to SU(8) spin-flavor symmetry plus a suitable symmetry breaking. The model produces resonances with negative parity from $s$-wave interaction of pseudoscalar and vector mesons with $1/2^{+}$ and $3/2^{+}$ baryons. Resonances in all the isospin, spin, and strange sectors with one, two, and three charm units are studied. Our results are compared with experimental data from several facilities, such as the CLEO, Belle or BABAR collaborations, as well as with other theoretical models. Some of our dynamically-generated states can be readily assigned to resonances found experimentally, while others do not have a straightforward identification and require the compilation of more data and also a refinement of the model. In particular, we identify the ${\Xi }_c(2790)$ and ${\Xi }_c(2815)$ resonances as possible candidates for a heavy-quark spin symmetry doublet.

We calculate the transverse correlation of fluctuations of the deposited energy density in nuclear collisions in the framework of a Gaussian model similar to the color glass condensate model.

We show that because of the multinucleon mechanism effects, the algorithm used to reconstruct the neutrino energy is not adequate when dealing with quasielastic-like events, and a distortion of the total flux-unfolded cross-section shape is produced. This amounts to a redistribution of strength from high to low energies, which gives rise to a sizable excess (deficit) of low (high) energy neutrinos. This distortion of the shape leads to a good description of the MiniBooNE unfolded charged current quasielastic-like cross sections published by A. A. Aguilar-Arevalo et al. [(MiniBooNE Collaboration), Phys. Rev. D 81, 092005 (2010)]. However, these changes in the shape are artifacts of the unfolding process that ignores multinucleon mechanisms.

Based on a data sample of $106\times {10}^6$ ${\psi }^{\prime }$ events collected with the BESIII detector, the decays ${\psi }^{\prime }\to \gamma {\chi }_{c0,2}$, ${\chi }_{c0,2}\to \gamma \gamma$ are studied to determine the two-photon widths of the ${\chi }_{c0,2}$ states. The two-photon decay branching fractions are determined to be $\mathcal{B}({\chi }_{c0}\to \gamma \gamma )=(2.24\pm 0.19\pm 0.12\pm 0.08)\times {10}^{-4}$ and $\mathcal{B}({\chi }_{c2}\to \gamma \gamma )=(3.21\pm 0.18\pm 0.17\pm 0.13)\times {10}^{-4}$. From these, the two-photon widths are determined to be ${\Gamma }_{\gamma \gamma }({\chi }_{c0})=(2.33\pm 0.20\pm 0.13\pm 0.17)\mathrm{keV}$, ${\Gamma }_{\gamma \gamma }({\chi }_{c2})=(0.63\pm 0.04\pm 0.04\pm 0.04)\mathrm{keV}$, and $\mathcal{R}={\Gamma }_{\gamma \gamma }({\chi }_{c2})/{\Gamma }_{\gamma \gamma }({\chi }_{c0})=0.271\pm 0.029\pm 0.013\pm 0.027$, where the uncertainties are statistical, systematic, and those from the PDG $\mathcal{B}({\psi }^{\prime }\to \gamma {\chi }_{c0,2})$ and $\Gamma ({\chi }_{c0,2})$ errors, respectively. The ratio of the two-photon widths for helicity $\lambda =0$ and helicity $\lambda =2$ components in the decay ${\chi }_{c2}\to \gamma \gamma$ is measured for the first time to be $f_{0/2}={\Gamma }_{\gamma \gamma }^{\lambda =0}({\chi }_{c2})/{\Gamma }_{\gamma \gamma }^{\lambda =2}({\chi }_{c2})=0.00\pm 0.02\pm 0.02$.

A coding error was found in our original version of numerical-relativity code SACRA. We correct the results of [M. Shibata, K. Kyutoku, T. Yamamoto, and K. Taniguchi, Phys. Rev. D 79, 044030 (2009).] by simulations of the improved accuracy.

We compute four-point functions of the stress tensor and conserved currents in ${\mathrm{AdS}}_4/{\mathrm{CFT}}_3$ using bulk perturbation theory. We work at tree-level in the bulk theory, which we take to be either pure gravity or Yang-Mills theory in AdS. We bypass the tedious evaluation of Witten diagrams using recently developed recursion relations for these correlators. In this approach, the four-point function is obtained as the sum of residues of a rational function at easily identifiable poles. We write down an explicit formula for the four-point correlator with arbitrary external helicities and momenta. We verify that, precisely as conjectured in a companion paper, the Maximally Helicity Violating (MHV) amplitude of gravitons or gluons appears as the coefficient of a specified singularity in the MHV stress-tensor or current correlator. We comment on the remarkably simple analytic structure of our answers in momentum space.

We present a consistent Bogomol’nyi-Prasad-Sommerfield (BPS) framework for a generalized Maxwell-Chern-Simons-Higgs model. The overall model, including its self-dual potential, depends on three different functions, $h(|\varphi |,N)$, $w(|\varphi |)$, and $G(|\varphi |)$, which are functions of the scalar fields only. The BPS energy is proportional to the magnetic flux when $w(|\varphi |)$ and $G(|\varphi |)$ are related to each other by a differential constraint. We present an explicit nonstandard model and its topologically nontrivial static configurations, which are described by the usual radially symmetric profile. Finally, we note that the nonstandard results behave in a similar way as their standard counterparts, as expected, reinforcing the consistence of the overall construction.

For a Gaussian spectrum of primordial density fluctuations, ultracompact minihalos (UCMHs) of dark matter are expected to be produced in much greater abundance than, e.g., primordial black holes. Forming shortly after matter-radiation equality, these objects would develop very dense and spiky dark matter profiles. In the standard scenario where dark matter consists of thermally produced, weakly interacting massive particles, UCMHs could thus appear as highly luminous gamma-ray sources or leave an imprint in the cosmic microwave background by changing the reionization history of the Universe. We derive corresponding limits on the cosmic abundance of UCMHs at different epochs and translate them into constraints on the primordial power spectrum. We find the resulting constraints to be quite severe, especially at length scales much smaller than what can be directly probed by the cosmic microwave background or large-scale structure observations. We use our results to provide an updated compilation of the best available constraints on the power of density fluctuations on all scales, ranging from the present-day horizon to scales more than 20 orders of magnitude smaller.

The effect of string- and quantum-gravity-inspired minimum-length deformed quantization on a free, massless scalar field is studied on the de Sitter background at the level of second quantization. An analytic solution of a field operator is obtained to the first order in deformation parameter. Using this solution, we then estimate the two-point and four-point correlation functions (with respect to the Bunch-Davies vacuum). The field operator shows up a nonlinear dependence on creation and annihilation operators, therefore the perturbation spectrum proves to be non-Gaussian. The correction to the power spectrum is of the same order as obtained previously in a similar study that incorporates the minimum-length deformed momentum operator into the first quantization picture and then proceeds in the standard way for second quantization. The non-Gaussianity comes at the level of four-point correlation function; its magnitude appears to be suppressed by the factor $\sim \exp (-6N)$, where $N$ is the number of e-foldings.

We apply a U-duality based solution-generating technique to construct supergravity solutions which describe nonextremal D5-branes and fluxbranes on various gravitational instantons. This includes an F7-brane wrapped on a sphere, which remains weakly coupled in the asymptotic region. We construct various superpositions of nonextremal D5-branes and fluxbranes that have angular momentum fixed by the parameters associated with their mass and two magnetic charges.

Gravity is usually considered to be irrelevant as far as the physics of elementary particles is concerned and, in particular, in the context of the spontaneous symmetry breaking (SSB) mechanism. We describe a version of the SSB mechanism in which gravity plays a direct role. We work in the context of diffeomorphism invariant gauge theories, which exist for any nonabelian gauge group $G$, and which have second-order in derivatives field equations. We show that any (nontrivial) vacuum solution of such a theory gives rise to an embedding of the group SU(2) into $G$, and thus breaks $G$ down to SU(2) times its centralizer in $G$. The components of the connection charged under SU(2) can then be seen to describe gravitons, with the SU(2) itself playing the role of the chiral half of the Lorentz group. Components charged under the centralizer describe the usual Yang-Mills gauge bosons. The remaining components describe massive particles. This breaking of symmetry explains (in the context of models considered) how gravity and Yang-Mills can come from a single underlying theory while being so different in the physics they describe. Further, varying the vacuum solution, and thus the embedding of SU(2) into $G$, one can break the Yang-Mills gauge group as desired, with massless gauge bosons of one vacuum acquiring mass in another. There is no Higgs field in our version of the SSB mechanism, the only variable is a connection field. Instead of the symmetry breaking by a dedicated Higgs field pointing in some direction in the field space, our theories break the symmetry by choosing how the group of internal gauge rotations of gravity (the chiral half of the Lorentz group) sits inside the full gauge group.

We consider a phase transition induced by the growth of Q-balls in a false vacuum. Such a transition could occur in the early universe in the case of broken supersymmetry with a metastable false vacuum. Small Q-balls with a negative potential energy can grow in a false vacuum by accretion of global charge until they reach critical size, expand, and cause a phase transition. We consider the growth of Q-balls from small to large, using the Bethe-Salpeter equation to describe small charge solitons and connecting to the growth of larger solitons for which the semiclassical approximation is reliable. We thus test the scenario in a simplified example inspired by supersymmetric extensions of the standard model.

We discuss the dependence of observables on the chemical potential in ’t Hooft’s large-$N$ QCD. To this end, we use the worldline formalism to expand the fermionic determinant in powers of $1/N$. We consider the hadronic as well as the deconfining phase of the theory. We discuss the origin of the sign problem in the worldline approach and elaborate on the planar equivalence between QCD with a baryon chemical potential and QCD with an isospin chemical potential. We show that for C-even observables, the sign problem occurs at a subleading order in the $1/N$ expansion of the fermionic determinant. Finally, we comment on the finite $N$ theory.

We investigate the spontaneous pair production—including the Schwinger mechanism and the Hawking thermal radiation—of charged scalar particles from the near-horizon region of a (near) extremal Reissner-Nordström black hole. The paradigm is equivalent to the dynamics of the charged scalar field in a specific ${\mathrm{AdS}}_2\times S^2$ spacetime with a constant electric field. Two possible boundary conditions are adopted to explicitly compute the corresponding production rate and absorption cross section. It is shown that the Schwinger production rate can be eventually suppressed by the increasing attractive gravitational force as the geometry changes from the extremal to the near extremal black hole. Consequently, the Schwinger mechanism and the Hawking radiation are generically indistinguishable for the near-extremal black holes. The holographic description dual to the pair production is also briefly discussed.

We present higher-derivative gravities that propagate an arbitrary number of gravitons of different mass on (anti-)de Sitter backgrounds. These theories have multiple critical points, at which the masses degenerate and the graviton energies are non-negative. For six derivatives and higher there are critical points with positive energy.

We investigate the effects of light cone caustics on the propagation of linear scalar fields in generic four-dimensional spacetimes. In particular, we analyze the singular structure of relevant Green functions. As expected from general theorems, Green functions associated with wave equations are globally singular along a large class of null geodesics. Despite this, the “nature” of the singularity on a given geodesic does not necessarily remain fixed. It can change character on encountering caustics of the light cone. These changes are studied by first deriving global Green functions for scalar fields propagating on smooth plane wave spacetimes. We then use Penrose limits to argue that there is a sense in which the “leading order singular behavior” of a (typically unknown) Green function associated with a generic spacetime can always be understood using a (known) Green function associated with an appropriate plane wave spacetime. This correspondence is used to derive a simple rule describing how Green functions change their singular structure near some reference null geodesic. Such changes depend only on the multiplicities of the conjugate points encountered along the reference geodesic. Using $\sigma (p,p^{\prime })$ to denote a suitable generalization of Synge’s world function, conjugate points with multiplicity 1 convert Green function singularities involving $\delta (\sigma )$ into singularities involving $\pm 1/\pi \sigma$ (and vice versa). Conjugate points with multiplicity 2 may be viewed as having the effect of two successive passes through conjugate points with multiplicity 1. Separately, we provide an extensive review of plane wave geometry that may be of independent interest. Explicit forms for bitensors such as Synge’s function, the van Vleck determinant, and the parallel and Jacobi propagators are derived almost everywhere for all nonsingular four-dimensional plane waves. The asymptotic behaviors of various objects near caustics are also discussed.

Brown [Phys. Rev. D 79, 104029 (2009)] has recently introduced a covariant formulation of the BSSN equations which is well suited for curvilinear coordinate systems. This is particularly desirable as many astrophysical phenomena are symmetric with respect to the rotation axis or are such that curvilinear coordinates adapt better to their geometry. However, the singularities associated with such coordinate systems are known to lead to numerical instabilities unless special care is taken (e.g., regularization at the origin). Cordero-Carrión will present a rigorous derivation of partially implicit Runge-Kutta methods in forthcoming papers, with the aim of treating numerically the stiff source terms in wavelike equations that may appear as a result of the choice of the coordinate system. We have developed a numerical code solving the BSSN equations in spherical symmetry and the general relativistic hydrodynamic equations written in flux-conservative form. A key feature of the code is that it uses a second-order partially implicit Runge-Kutta method to integrate the evolution equations. We perform and discuss a number of tests to assess the accuracy and expected convergence of the code—namely a pure gauge wave, the evolution of a single black hole, the evolution of a spherical relativistic star in equilibrium, and the gravitational collapse of a spherical relativistic star leading to the formation of a black hole. We obtain stable evolutions of regular spacetimes without the need for any regularization algorithm at the origin.

We point out the existing confusion about the slowroll parameters and conditions for multifield inflation. If one requires the fields to roll down the gradient flow, we find that only articles adopting the Hubble slowroll expansion are on the right track, and a correct condition can be found in a recent book by Liddle and Lyth [The Primordial Density Perturbation: Cosmology, Inflation and the Origin of Structure (Cambridge University Press, Cambridge, England, 2009)]. We further analyze this condition and show that the gradient flow requirement is stronger than just asking for a slowly changing, quasi-de Sitter solution. Therefore, it is possible to have a multifield slowroll model that does not follow the gradient flow. Consequently, it no longer requires the gradient to be small. It even bypasses the first slowroll condition and some related no-go theorems from string theory. We provide the “spiral inflation” as a generic blueprint of such an inflation model and show that it relies on a monodromy locus, a common structure in string theory effective potentials.