We exploit the quantum coherence between pair-produced $D^0$ and ${\overline{D}}^0$ in $\psi (3770)$ decays to make a first determination of the relative strong phase differences between $D^0\to K_S^0{\pi }^{+}{\pi }^{-}$ and ${\overline{D}}^0\to K_S^0{\pi }^{+}{\pi }^{-}$, which are of great importance in determining the Cabibbo-Kobayashi-Maskawa angle $\gamma /{\varphi }_3$ in $B^{-}\to D^0({\overline{D}}^0)K^{-}$ decays. Using $818{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected with the CLEO-c detector at $E_{\mathrm{cm}}=3.77\mathrm{GeV}$, we employ a binned Dalitz-plot analysis of $K_S^0{\pi }^{+}{\pi }^{-}$ and $K_L^0{\pi }^{+}{\pi }^{-}$ decays recoiling against flavor-tagged, $CP$-tagged, and $K_S^0{\pi }^{+}{\pi }^{-}$-tagged events to determine these strong phase differences.

In this paper we continue the study of nonrelativistic $p+1$ dimensional theories that we started in [arXiv:0904.1343]. We extend the analysis presented there to the case of stable and unstable Dp-branes.

In asymmetrically-warped spacetimes different warp factors are assigned to space and to time. We discuss causality properties of these warped brane universes and argue that scenarios with two extra dimensions may allow for timelike curves which can be closed via paths in the extra-dimensional bulk. In particular, necessary and sufficient conditions on the metric for the existence of closed timelike curves are presented. We find a six-dimensional warped metric which satisfies the CTC conditions, and where the null, weak and dominant energy conditions are satisfied on the brane (although only the former remains satisfied in the bulk). Such scenarios are interesting, since they open the possibility of experimentally testing the chronology protection conjecture by manipulating on our brane initial conditions of gravitons or hypothetical gauge-singlet fermions (“sterile neutrinos”) which then propagate in the extra dimensions.

We take the first steps in a systematic study of group field theory (GFT) renormalization, focusing on the Boulatov model for 3D quantum gravity. We define an algorithm for constructing the 2D triangulations that characterize the boundary of the 3D bubbles, where divergences are located, of an arbitrary 3D GFT Feynman diagram. We then identify a special class of graphs for which a complete contraction procedure is possible, and prove, for these, a complete power counting. These results represent important progress towards understanding the origin of the continuum and manifoldlike appearance of quantum spacetime at low energies, and of its topology, in a GFT framework.

We consider a probe codimension-2 brane inflation scenario in a warped six-dimensional flux compactification. Our background model is Salam-Sezgin gauged supergravity with codimension-2 brane sources, which preserve $\mathcal{N}=1$ supersymmetry. The model has a modulus, which is stabilized by means of a cap regularization of the codimension-2 singularities, with appropriate dilaton potentials on the ring interface of the caps with the bulk. We discuss the cosmological evolution of the worldvolume of a probe codimension-2 brane when it moves along the radial direction of the internal space. In order to have slow-roll inflation, one needs the warping of the internal space to be weak, in contrast to the recent string inflation constructions with strong warping. We discuss the parameter range that the inflation is in agreement with the observationally inferred parameters and which furthermore is consistent with the probe-brane approximation. We provide arguments pointing that the probe-brane approximation is a good assumption if the probe-brane is not exactly conical and show with a multibrane solution that the mild warping needed for a slow-roll inflation is not spoiled by the probe brane.

This paper reports on an all-sky search for periodic gravitational waves from sources such as deformed isolated rapidly spinning neutron stars. The analysis uses 840 hours of data from 66 days of the fifth LIGO science run (S5). The data were searched for quasimonochromatic waves with frequencies $f$ in the range from 50 to 1500 Hz, with a linear frequency drift $\dot{f}$ (measured at the solar system barycenter) in the range $-f/\tau <\dot{f}<0.1f/\tau$, for a minimum spin-down age $\tau$ of 1000 years for signals below 400 Hz and 8000 years above 400 Hz. The main computational work of the search was distributed over approximately 100 000 computers volunteered by the general public. This large computing power allowed the use of a relatively long coherent integration time of 30 hours while searching a large parameter space. This search extends Einstein@Home’s previous search in LIGO S4 data to about 3 times better sensitivity. No statistically significant signals were found. In the 125–225 Hz band, more than 90% of sources with dimensionless gravitational-wave strain tensor amplitude greater than $3\times {10}^{-24}$ would have been detected.

The gauge sector of the standard model exhibits a flavor symmetry that allows for independent unitary transformations of the fermion multiplets. In the standard model the flavor symmetry is broken by the Yukawa couplings to the Higgs boson, and the resulting fermion masses and mixing angles show a pronounced hierarchy. In this work we connect the observed hierarchy to a sequence of intermediate effective theories, where the flavor symmetries are broken in a stepwise fashion by vacuum expectation values of suitably constructed spurion fields. We identify the possible scenarios in the quark sector and discuss some implications of this approach.

A low-energy nonunitary leptonic mixing matrix is a generic feature of many extensions of the standard model. In such a case, the task of future precision neutrino oscillation experiments is more ambitious than measuring the three mixing angles and the leptonic (Dirac) $CP$ phase, i.e., the accessible parameters of a unitary leptonic mixing matrix. A nonunitary mixing matrix has 13 parameters that affect neutrino oscillations, out of which four are $CP$ violating. In the scheme of minimal unitarity violation we analyze the potential of a neutrino factory for determining or constraining the parameters of the nonunitary leptonic mixing matrix, thereby testing the origin of $CP$ violation in the lepton sector.

Motivated by possible extensions of the braneworld models with two branes, we investigate some consequences of a variable brane tension, using the well established results on consistency conditions. By a slight modification of the usual stress-tensor used in order to derive the braneworld sum rules, we find some important constraints obeyed by time-dependent brane tensions. In particular, it is shown that the tensions of two Randall-Sundrum–like branes obeying, at the same time, an Eötvös law, aggravate the fine-tuning problem. Also, it is shown that if the hidden brane tension obeys an Eötvös law, then the visible brane has a mixed behavior allowing a bouncinglike period at early times while it is dominated by an Eötvös law now. To finalize, we discuss some qualitative characteristics, which may arise in the scope of dynamical brane tensions, as anisotropic background and branons production.

We consider the behavior of open strings on anti-de Sitter wormholes in Gauss-Bonnet theory, which are the Gauss-Bonnet gravity duals of a pair of field theories. A string with both endpoints on the same side of the wormhole describes two charges within the same field theory, which exhibit Coulomb interaction for small separation. On the other hand, a string extending through the wormhole describes two charges which live in different field theories, and they exhibit a springlike confining potential. A transition occurs when there is a pair of charges present within each field theory: for small separation each pair of charges exhibits Coulomb interaction, while for large separation the charges in the different field theories pair up and exhibit confinement. Two steadily-moving charges in different field theories can occupy the same location provided that their speed is less than a critical speed, which also plays the role of a subluminal speed limit. However, for some wormhole backgrounds, charges moving at the critical speed cannot occupy the same location and energy is transferred from the leading charge to the lagging one. We also show that strings on anti-de Sitter wormholes in supergravity theories without higher-derivative curvature terms can exhibit these properties as well.

In this paper we investigate the manner in which the internal spin angular momentum of a spinor field is encoded in the gravitational field at asymptotic infinity. The inclusion of internal spin requires us to reanalyze our notion of asymptotic flatness. In particular, the Poincaré symmetry at asymptotic infinity must be replaced by a spin-enlarged Poincaré symmetry. Likewise, the generators of the asymptotic symmetry group must be supplemented to account for the internal spin. In the Hamiltonian framework of first-order Einstein-Cartan gravity, the extra generator comes from the boundary term of the Gauss constraint in the asymptotically flat context. With the additional term, we establish the relations among the Noether charges of a Dirac field, the Komar integral, and the asymptotic Arnowitt-Deser-Misner-like geometric integral. We show that by imposing mild restraints on the generating functionals of gauge transformations at asymptotic infinity, the phase space is rendered explicitly finite. We construct the energy-momentum and the new total ($\mathrm{\text{spin}}+\mathrm{\text{orbital}}$) angular momentum boundary integrals that satisfy the appropriate algebra to be the generators of the spin-enlarged Poincaré symmetry. This demonstrates that the internal spin is encoded in the tetrad at asymptotic infinity. In addition, we find that a new conserved and (spin-enlarged) Poincaré invariant charge emerges that is associated with the global structure of a gauge transformation.

The hypothesis of path integral duality provides a prescription to evaluate the propagator of a free, quantum scalar field in a given classical background, taking into account the existence of a fundamental length, say, the Planck length $L_{\mathrm{P}}$ in a locally Lorentz invariant manner. We use this prescription to evaluate the duality modified propagators in spacetimes with constant curvature (exactly in the case of one spacetime, and in the Gaussian approximation for another two), and show that (i) the modified propagators are ultraviolet finite, (ii) the modifications are nonperturbative in $L_{\mathrm{P}}$, and (iii) $L_{\mathrm{P}}$ seems to behave like a “zero point length” of spacetime intervals such that $⟨{\sigma }^2(x,x^{\prime })⟩=[{\sigma }^2(x,x^{\prime })+\mathcal{O}(1)L_{\mathrm{P}}^2]$, where $\sigma (x,x^{\prime })$ is the geodesic distance between the two spacetime points $x$ and $x^{\prime }$, and the angular brackets denote (a suitable) average over the quantum gravitational fluctuations. We briefly discuss the implications of our results.

Approximate analytical solutions of the Boltzmann equation for particles that are either extremely relativistic or nonrelativistic when they decouple from the thermal bath are well established. However, no analytical formula for the relic density of particles that are semirelativistic at decoupling is yet known. We propose a new ansatz for the thermal average of the annihilation cross sections for such particles, and find a semianalytical treatment for calculating their relic densities. As examples, we consider Majorana- and Dirac-type neutrinos. We show that such semirelativistic relics cannot be good cold dark matter candidates. However, late decays of metastable semirelativistic relics might have released a large amount of entropy, thereby diluting the density of other, unwanted relics.

We study the generation of vorticity and velocity dispersion by orbit crossing using cosmological numerical simulations, and calculate the backreaction of these effects on the evolution of large-scale density and velocity divergence power spectra. We use Delaunay tessellations to define the velocity field, showing that the power spectra of velocity divergence and vorticity measured in this way are unbiased and have better noise properties than for standard interpolation methods that deal with mass-weighted velocities. We show that high resolution simulations are required to recover the correct large-scale vorticity power spectrum, while poor resolution can spuriously amplify its amplitude by more than 1 order of magnitude. We measure the scalar and vector modes of the stress tensor induced by orbit crossing using an adaptive technique, showing that its vector modes lead, when input into the vorticity evolution equation, to the same vorticity power spectrum obtained from the Delaunay method. We incorporate orbit-crossing corrections to the evolution of large-scale density and velocity fields in perturbation theory by using the measured stress tensor modes. We find that at large scales ($k\simeq 0.1h{\mathrm{Mpc}}^{-1}$) vector modes have very little effect in the density power spectrum, while scalar modes (velocity dispersion) can induce percent-level corrections at $z=0$, particularly in the velocity divergence power spectrum. In addition, we show that the velocity power spectrum is smaller than predicted by linear theory until well into the nonlinear regime, with little contribution from virial velocities.

To explain the accelerated expansion of the late universe, the $1/R$ correction to Einstein gravity is usually considered, where $R$ is the Ricci scalar. This correction term, if stable, is generally believed to be negligible during inflation. However, if the $1/R$ term is inflaton dependent, it will dramatically change the story of inflation. The entropy perturbation will naturally appear and drive the evolution of curvature perturbation outside the Hubble horizon. In a large class of models, the entropy perturbation can be made nearly scale invariant. In Einstein gravity the single-field inflation with a quartic potential has been ruled out by recent observations, but it revives when the $1/R$ term is turned on. The evolution of non-Gaussianities on a large scale are also studied and applied to inflation with $1/R$ correction. In some specific models, a large non-Gaussianity can be naturally generated outside the horizon. A recent study ruled out almost all $f(R)$ models during the matter-dominated phase. Taking this into consideration, we are left with a limited class of model which recovers the Einstein gravity soon after reheating.

Integrable structure of the symmetry reduced dynamics of massless bosonic sector of the heterotic string effective action is presented. For string background equations that govern in the space-time of $D$ dimensions ($D\ge 4$), the dynamics of interacting gravitational, dilaton, antisymmetric tensor and any number $n\ge 0$ of Abelian vector gauge fields, all depending only on two coordinates, we construct an equivalent $(2d+n)\times (2d+n)$-matrix spectral problem ($d=D-2$). This spectral problem provides the base for the development of various solution constructing procedures (dressing transformations, integral equation methods). For the case of the absence of Abelian gauge fields, we present the soliton generating transformations of any background with interacting gravitational, dilaton, and the second rank antisymmetric tensor fields.

Working in the linear sigma model with quarks, we compute the finite-temperature effective potential in the presence of a weak magnetic field, including the contribution of the pion ring diagrams and considering the sigma as a classical field. In the approximation where the pion self-energy is computed perturbatively, we show that there is a region of the parameter space where the effect of the ring diagrams is to preclude the phase transition from happening. Inclusion of the magnetic field has small effects that however become more important as the system evolves to the lowest temperatures allowed in the analysis.

Although empirical evidence indicates that the Universe’s gas had become ionized by redshift $z\approx 6$, the mechanism by which this transition occurred remains unclear. In this article, we explore the possibility that dark matter annihilations may have played the dominant role in this process. Energetic electrons produced in these annihilations can scatter with the cosmic microwave background to generate relatively low energy gamma rays, which ionize and heat gas far more efficiently than higher energy prompt photons. In contrast to previous studies, we find that viable dark matter candidates with electroweak scale masses can naturally provide the dominant contribution to the reionization of the Universe. Intriguingly, we find that dark matter candidates capable of producing the recent cosmic ray positron excesses observed by PAMELA (or the electrons spectrum measured by the Fermi Gamma Ray Space Telescope) are also predicted to lead to the full reionization of the Universe by $z\sim 6$.

We present a supersymmetric extension of the standard model (USSM-A) with an anomalous $U(1)$ and Stückelberg axions for anomaly cancellation, generalizing similar nonsupersymmetric constructions. The model, built by a bottom-up approach, is expected to capture the low-energy supersymmetric description of axionic symmetries in theories with gauged anomalous Abelian interactions, previously explored in the nonsupersymmetric case for scenarios with intersecting branes. The choice of a USSM-like superpotential, with one extra singlet superfield and an extra Abelian symmetry, allows a physical axionlike particle in the spectrum. We describe some general features of this construction and, in particular, the modification of the dark-matter sector which involves both the axion and several neutralinos with an axino component. The axion is expected to be very light in the absence of phases in the superpotential but could acquire a mass which can also be in the few GeV range or larger. In particular, the gauging of the anomalous symmetry allows independent mass/coupling interaction to the gauge fields of this particle, a feature which is absent in traditional (invisible) axion models. We comment on the general implications of our study for the signature of moduli from string theory due to the presence of these anomalous symmetries.