The phase transition of Reissner-Nordström $\mathrm{Ad}{\mathrm{S}}_4$ interacting with a massive charged scalar field has been further revisited. We found exactly one stable and one unstable quasinormal mode region for the scalar field. The two of them are separated by the first marginally stable solution.

Cosmological models where the standard big bang is replaced by a bounce have been studied for decades. The situation has, however, dramatically changed in the past years for two reasons: first, because new ways to probe the early Universe have emerged, in particular, thanks to the cosmic microwave background, and second, because some well grounded theories—especially loop quantum cosmology—unambiguously predict a bounce, at least for homogeneous models. In this article, we investigate into the details the phenomenological parameters that could be constrained or measured by next-generation $B$-mode cosmic microwave background experiments. We point out that an important observational window could be opened. We then show that those constraints can be converted into very meaningful limits on the fundamental loop quantum cosmology parameters. This establishes the early Universe as an invaluable quantum gravity laboratory.

The chemical composition of ultrahigh energy cosmic rays is a key question in particle astrophysics. The measured composition, inferred from the elongation rates of cosmic ray showers, looks in general very different from the initial source composition: resonant photo-disintegration in the cosmic radiation background proceeds rapidly at the highest energies and the initial composition quickly becomes lighter during propagation. For a statistical analysis of continuously improving cosmic ray data it is desirable to know the secondary spectra as precisely as possible. Here, we discuss exact analytic solutions of the evolution equation of ultrahigh energy cosmic ray nuclei. We introduce a diagrammatic formalism that leads to a systematic analytic expansion of the exact solution in terms of second order effects of the propagation. We show how the first order corrections of this expansion can improve the predictions of secondary spectra in a semianalytical treatment.

The direct observation of gravitational waves will provide a unique tool for probing the dynamical properties of highly compact astrophysical objects, mapping ultrarelativistic regions of space-time, and testing Einstein’s general theory of relativity. LISA (Laser Interferometer Space Antenna), a joint National Aeronautics and Space Administration and European Space Agency mission to be launched in the next decade, will perform these scientific tasks by detecting and studying low-frequency cosmic gravitational waves through their influence on the phases of six modulated laser beams exchanged between three remote spacecraft. By directly measuring the polarization components of the waves LISA will detect, we will be able to test Einstein’s theory of relativity with good sensitivity. Since a gravitational wave signal predicted by the most general relativistic metric theory of gravity accounts for six polarization modes (the usual two Einstein’s tensor polarizations as well as two vector and two scalar wave components), we have derived the LISA time-delay interferometric responses and estimated their sensitivities to vector- and scalar-type waves. We find that (i) at frequencies larger than roughly the inverse of the one-way light time ($\approx 6\times {10}^{-2}\mathrm{Hz}$), LISA is more than ten times sensitive to scalar-longitudinal and vector signals than to tensor and scalar-transverse waves, and (ii) in the low part of its frequency band is equally sensitive to tensor and vector waves and somewhat less sensitive to scalar signals.

If the excess events from the CoGeNT experiment arise from elastic scatterings of a light dark matter off the nuclei, crossing symmetry implies nonvanishing annihilation cross sections of the light dark matter into hadronic final states inside the Galactic halo, which we confront with the antiproton spectrum measured by the PAMELA Collaboration. We consider two types of effective interactions between the dark matter and the quarks: (1) contact interactions from integrating out heavy particles and (2) long-range interactions due to the electromagnetic properties of the dark matter. The lack of excess in the antiproton spectrum results in tensions for a scalar and, to a lesser extent, vector dark matter interacting with the quarks through the Higgs portal.

One of the prime tools to search for new light bosons interacting very weakly with photons—prominent examples are axions, axionlike particles, and extra “hidden” U(1) gauge bosons—are light-shining-through-a-wall experiments. With the current generation of these experiments finishing data taking it is time to plan for the next and search for an optimal setup. The main challenges are clear: on the one hand we want to improve the sensitivity towards smaller couplings, on the other hand we also want to increase the mass range to which the experiments are sensitive. Our main example is axion(like particle)s but we also discuss implications for other WISPs (weakly interacting slim particles) such as hidden U(1) gauge bosons. To improve the sensitivity for axions towards smaller couplings, one can use multiple magnets to increase the length of the interaction region. However, naively the price to pay is that the mass range is limited to smaller masses. We discuss how one can optimize the arrangement of magnets (both in field direction as well as allowing for possible gaps in between) to ameliorate this problem. Moreover, future experiments will include resonant, high quality optical cavities in both the production and the regeneration region. To achieve the necessary high quality of the cavities we need to avoid too high diffraction losses. This leads to minimum requirements on the diameter of the laser beam and therefore on the aperture of the cavity. We investigate what can be achieved with currently available magnets and desirable features for future ones.

Heavy neutral resonances appearing in the clean Drell-Yan channel may be the first new physics to be observed at the proton-proton CERN LHC. If a new resonance is discovered at the LHC as a (narrow) peak in the dilepton invariant mass distribution, the characterization of its spin and couplings will proceed via the measurement of production rates and angular distributions of the decay products. We discuss the discrimination of a spin-0 resonance (sneutrino) predicted by supersymmetric theories with $R$-parity breaking against the spin-1 of $Z^{\prime }$ bosons and the Randall-Sundrum graviton resonance (spin-2) with the same mass and producing the same number of events under the observed peak. To assess the region of sneutrino parameters (couplings and masses) where the spin determination can be performed to a given confidence level, we focus on the event rate and the angular distributions of the Drell-Yan leptons, in particular, using the center-edge asymmetry, $A_{\mathrm{CE}}$. We find that although the measured event rate permits solving the above problem partially, the center-edge asymmetry, on the contrary allows one to differentiate the various spins entirely with a minimal number of events around 200.

We measure on the lattice the quenched pseudoscalar and vector meson masses at a fixed value of the lattice spacing for $\mathrm{SU}(N)$ gauge theory with fermions in the adjoint, in the symmetric and in the antisymmetric representation of the gauge group. Simulations are performed for $N=3$, 4, 6 in all those representations, with the addition of $N=2$ for the adjoint representation. We illustrate a strategy for separating the even from the odd-power contributions in $1/N$ in the masses. Using this technique, we extrapolate the vector mass to the large-$N$ limit in the chiral region and show that at $N=\infty$ this mass is the same within errors in all the three representations, as predicted by orientifold planar equivalence. Possible implications of our investigation for studying orientifold planar equivalence in the dynamical case are discussed.

We present results for the kaon mixing parameter $B_K$ calculated using HYP (hypercubic fat link)-smeared improved staggered fermions on the asqtad lattices generated by the MILC collaboration. We use three lattice spacings ($a\approx 0.12$, 0.09 and 0.06 fm), ten different valence-quark masses ($m\approx m_s/10-m_s$), and several light sea-quark masses in order to control the continuum and chiral extrapolations. We derive the next-to-leading order staggered chiral perturbation theory (SChPT) results necessary to fit our data, and use these results to do extrapolations based both on SU(2) and SU(3) SChPT. The SU(2) fitting is particularly straightforward because parameters related to taste breaking and matching errors appear only at next-to-next-to-leading order. We match to the continuum renormalization scheme [naïve dimensional regularization (NDR)] using one-loop perturbation theory. Our final result is from the SU(2) analysis, with the SU(3) result providing a (less accurate) cross check. We find $B_K(\mathrm{NDR},\mu =2\mathrm{GeV})=0.529\pm 0.009\pm 0.032$ and ${\widehat{B}}_K=B_K(\mathrm{RGI})=0.724\pm 0.012\pm 0.043$, where the first error is statistical and the second systematic. The error is dominated by the truncation error in the matching factor. Our results are consistent with those obtained using valence domain-wall fermions on lattices generated with asqtad or domain-wall sea quarks.

We investigate the electromagnetic form factors of the $\Delta$ and the $\Omega$ baryons within the Poincaré-covariant framework of Dyson-Schwinger and Bethe-Salpeter equations. The three-quark core contributions of the form factors are evaluated by employing a quark-diquark approximation. We use a consistent setup for the quark-gluon dressing, the quark-quark bound-state kernel and the quark-photon interaction. Our predictions for the multipole form factors are compatible with available experimental data and quark model estimates. The current-quark mass evolution of the static electromagnetic properties agrees with results provided by lattice calculations.

In the two-quark model supposition for $K_0^{*}(1430)$, which can be viewed as either the first excited state (scenario  I) or the lowest lying state (scenario II), the branching ratios and the direct $CP$-violating asymmetries for decays ${\overline{B}}_s^0\to K_0^{*0}(1430)\varphi$, $K_0^{*0}(1430)\omega$, $K_0^{*0}(1430){\rho }^0$, $K_0^{*+}(1430){\rho }^{-}$ are studied by employing the perturbative QCD factorization approach. We find the following results: (a) Enhanced by the color allowed tree amplitude with large Wilson coefficients $a_1=C_2+C_1/3$, the branching ratio of ${\overline{B}}_s^0\to K_0^{*+}(1430){\rho }^{-}$ is much larger than those of the other three decays and arrives at $({3.4}_{-0.7}^{+0.8})\times {10}^{-5}$ in scenario I, even ${10}^{-4}$ order in scenario II, and its direct $CP$-violating asymmetry is the smallest, around 10%, so this channel might be measurable in the current LHC-b experiments, where a large number (about ${10}^{12}$) of $B$ mesons will be produced per year. These high statistics will make the measurement possible. (b) For the decay modes ${\overline{B}}_s^0\to K_0^{*0}(1430)\omega$, $K_0^{*0}(1430){\rho }^0$, their direct $CP$-violating asymmetries are large, but it might be difficult to measure them, because their branching ratios are small and less than (or near) ${10}^{-6}$ in both scenarios. For example, in scenario I, these values are $\mathcal{B}({\overline{B}}_s^0\to K_0^{*}(1430)\omega )=({8.2}_{-1.7}^{+1.8})\times {10}^{-7}$, $\mathcal{B}({\overline{B}}_s^0\to K_0^{*}(1430){\rho }^0)=({9.9}_{-2.0}^{+2.1})\times {10}^{-7}$, ${\mathcal{A}}_{CP}^{\mathrm{dir}}({\overline{B}}_s^0\to K_0^{*0}(1430)\omega )=-{24.1}_{-2.5}^{+2.8}$, ${\mathcal{A}}_{CP}^{\mathrm{dir}}({\overline{B}}_s^0\to K_0^{*0}(1430){\rho }^0)={26.6}_{-2.5}^{+2.5}$. (c) For the decay ${\overline{B}}_s^0\to K_0^{*}(1430)\varphi$, the predicted branching ratios are also small and a few times ${10}^{-7}$ in both scenarios; there is no tree contribution at the leading order, so its direct $CP$-violating asymmetry is naturally zero.

We write down exact solutions in the collective field theory of the $\mathrm{c}=1$ matrix model and in dilaton-gravity coupled to a massless scalar. Using a known correspondence between these two theories at the null boundaries of spacetime, we make a connection between scalar fields in these two theories in the bulk of spacetime. In the process, we gain insight into how a theory containing gravity can be equivalent to one without gravity. We analyze a simple time-dependent background as an example.

One loop expressions for fermion self-energy, vacuum polarization, and vertex correction in light-front time ordered perturbation theory can be obtained from respective covariant expressions by performing $k^{-}$ integration. In an earlier work, we have shown that the third term in the doubly transverse gauge propagator is necessary to generate the diagrams involving instantaneous photon exchange both in the case of fermion self-energy as well as vertex correction. In this work, using the two-term photon propagator, we show that the instantaneous photon exchange diagrams in fermion self-energy as well as the IR singular terms in the propagating diagrams can be generated by taking the asymptotic limit of the covariant expression. It is further shown that this method reproduces the IR singular terms in propagating diagrams of vacuum polarization also.

We study a heterotic two-dimensional $\mathcal{N}=(0,2)$ gauged nonlinear sigma-model whose target space is a weighted complex projective space. We consider the case with $N$ positively and $\tilde{N}=N_F-N$ negatively charged fields. This model is believed to give a description of the low-energy physics of a non-Abelian semilocal vortex in a four-dimensional $\mathcal{N}=2$ supersymmetric $U(N)$ gauge theory with $N_F>N$ matter hypermultiplets. The supersymmetry in the latter theory is broken down to $\mathcal{N}=1$ by a mass term for the adjoint fields. We solve the model in the large-$N$ approximation and explore a two-dimensional subset of the mass parameter space for which a discrete ${\mathbb{Z}}_{N-\tilde{N}}$ symmetry is preserved. Supersymmetry is generically broken, but it is preserved for special values of the masses where a new branch opens up and the model becomes superconformal.

We study free scalar field theory on flat spacetime using a background-independent (polymer) quantization procedure. Specifically we compute the propagator using a method that takes the energy spectrum and position matrix elements of the harmonic oscillator as inputs. We obtain closed form results in the infrared and ultraviolet regimes that give Lorentz invariance violating dispersion relations and show suppression of propagation at sufficiently high energy.

We study a holomorphic representation for spinfoams. The representation is obtained via the Ashtekar-Lewandowski-Marolf-Mourão-Thiemann coherent state transform. We derive the expression of the 4d spinfoam vertex for Euclidean and for Lorentzian gravity in the holomorphic representation. The advantage of this representation rests on the fact that the variables used have a clear interpretation in terms of a classical intrinsic and extrinsic geometry of space. We show how the peakedness on the extrinsic geometry selects a single exponential of the Regge action in the semiclassical large-scale asymptotics of the spinfoam vertex.

We classify all the six-derivative Lagrangians of gravity, whose traced field equations are of second or third order, in arbitrary dimensions. In the former case, the Lagrangian in dimensions greater than six reduces to an arbitrary linear combination of the six-dimensional Euler density and the two linearly independent cubic Weyl invariants. In five dimensions, besides the independent cubic Weyl invariant, we obtain an interesting cubic combination, whose field equations for static spherically symmetric spacetimes are of second order. In the latter case, in arbitrary dimensions we obtain two combinations, which in dimension three, are equivalent to the complete contraction of two Cotton tensors. Moreover, we also recover all the conformal anomalies in six dimensions. Finally, we present the general static, spherically symmetric solution for some of these Lagrangians.

We consider propagation of gravitational waves in a magnetized plasma, using the linearized Maxwell-Vlasov equations coupled to Einstein’s equations. A set of coupled electromagnetic-gravitational wave equations are derived that can be straightforwardly reduced to a single dispersion relation. We demonstrate that there is a number of different resonance effects that can enhance the influence of the plasma on the gravitational waves.