Exact expressions for quantum corrections to spinning strings

The one-loop worldsheet quantum corrections to the energy of spinning strings on R×S³$\mathbb{R}\times S^3$ within AdS₅×S⁵${\mathit{AdS}}_5\times S^5$ are reexamined. The explicit expansion in the effective 't Hooft coupling λ^′=λ/J²${\lambda }^{\prime }=\lambda /J^2$ is rigorously derived. The expansion contains both analytic and non-analytic terms in λ^′${\lambda }^{\prime }$, as well as exponential corrections. Furthermore, we pin down the origin of the terms that are not captured by the quantum string Bethe ansatz, which only produces analytic terms in λ^′${\lambda }^{\prime }$. It is shown that the analytic terms arise from string fluctuations within the S³$S^3$, whereas the non-analytic and exponential terms, which are not captured by the Bethe ansatz, originate from the fluctuations in all directions within the supersymmetric sigma model on AdS₅×S⁵${\mathit{AdS}}_5\times S^5$. We also comment on the case of spinning string in AdS₃×S¹${\mathit{AdS}}_3\times S^1$.     

On the anatomy of multi-spin magnon and single spike string solutions

We study rigid string solutions rotating in AdS₅×S⁵${\mathit{AdS}}_5\times S^5$ background. For particular values of the parameters of the solutions we find multispin solutions corresponding to giant magnons and single spike strings. We present an analysis of the dispersion relations in the case of three spin solutions distributed only in S⁵$S^5$ and the case of one spin in AdS₅${\mathit{AdS}}_5$ and two spins in S⁵$S^5$. The possible relation of these string solutions to gauge theory operators and spin chains are briefly discussed.     

Magnon-like dispersion relation from M-theory

We investigate classical rotating membranes in two different backgrounds. First, we obtain membrane solution in AdS₄×S⁷${\mathit{AdS}}_4\times S^7$ background, analogous to the solution obtained by Hofman and Maldacena in the case of string theory. We find a magnon type dispersion relation similar to that of Hofman and Maldacena and to the one found by Dorey for the two spin case. In the appendix of the paper, we consider membrane solutions in AdS₇×S⁴${\mathit{AdS}}_7\times S^4$, which give new relations between the conserved charges.     

Mesons and Higgs branch in defect theories

We consider the defect theory obtained by intersecting D3- and D5-branes along two common spatial directions. We work in the approximation in which the D5-brane is a probe in the AdS₅×S⁵${\mathit{AdS}}_5\times S^5$ background. By adding worldvolume flux to the D5-brane and choosing an appropriate embedding of the probe in AdS₅×S⁵${\mathit{AdS}}_5\times S^5$, one gets a supersymmetric configuration in which some of the D3-branes recombine with the D5-brane. We check this fact by showing that the D5-brane can be regarded as a system of polarized D3-branes. On the field theory side this corresponds to the Higgs branch of the defect theory, where some of the fundamental hypermultiplet fields living on the intersection acquire a vacuum expectation value. We study the spectrum of mesonic bound states of the defect theory in this Higgs branch and show that it is continuous and gapless.     

Ricci-flat and charged wormholes in five dimensions

We construct stationary Ricci-flat inter-universe Lorentzian wormhole solutions in all D?5$D?5$ dimensions that connect two flat asymptotic spacetimes. Such a solution can be viewed as the gravity dual of a string tachyon state whose linear momentum is larger than its tension. We focus our analysis on the D=5$D=5$ wormholes which are not traversable for the timelike and null geodesics; however, we demonstrate that there exist accelerated timelike trajectories that traverse from one asymptotic region to the other. We further study the minimally-coupled scalar wave equation and demonstrate that the quantum tunnelling between two worlds must occur. We also obtain charged wormholes in five-dimensional supergravities. With appropriate choice of parameters, these wormholes connect AdS₃×S²${\mathit{AdS}}_3\times S^2$ in one asymptotic region to flat Minkowskian spacetime in the other.     

Temperature quantization from the TBA equations

We analyze the Thermodynamic Bethe Ansatz equations for the mirror model which determine the ground state energy of the light-cone AdS₅×S⁵${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ superstring living on a cylinder. The light-cone momentum of string is equal to the circumference of the cylinder, and is identified with the inverse temperature of the mirror model. We show that the natural requirement of the analyticity of the Y-functions leads to the quantization of the temperature of the mirror model which has never been observed in any other models.     

Entropy of an extremal regular black hole

We introduce a magnetically charged extremal regular black hole in the coupled system of Einstein gravity and nonlinear electrodynamics. Its near horizon geometry is given by AdS₂×S²${\mathit{AdS}}_2\times S^2$. It turns out that the entropy function approach does not automatically lead to a correct entropy of the Bekenstein–Hawking entropy. This contrasts to the case of the extremal Reissner–Norström black hole in the Einstein–Maxwell theory. We conclude that the entropy function approach does not work for a magnetically charged extremal regular black hole without singularity, because of the nonlinearity of the entropy function.     

Cosmological Kaluza–Klein branes in black brane spacetimes

We discuss the cosmological evolution of a brane in the D(>6)$D(>6)$-dimensional black brane spacetime in the context of the Kaluza–Klein (KK) braneworld scheme, i.e., to consider KK compactification on the brane. The bulk spacetime is composed of two copies of a patch of D  -dimensional black three-brane solution. The near-horizon geometry is given by AdS₅×S(D−5)${\mathit{AdS}}_5\times S^{(D-5)}$ while in the asymptotic infinity the spacetime approaches D-dimensional Minkowski. We consider the brane motion from the near-horizon region toward the spatial infinity, which induces cosmology on the brane. As is expected, in the early times, namely when the brane is located in the near-horizon region, the effective cosmology on the brane coincides with that in the second Randall–Sundrum (RS II) model. Then, the brane cosmology starts to deviate from the RS type one since the dynamics of KK compactified dimensions becomes significant. We find that the brane Universe cannot reach the asymptotic infinity, irrespectively of the components of matter on the brane.     

Weyl anomaly of conformal higher spins on six-sphere

This paper is a sequel to arXiv:1309.0785 were we computed the Weyl anomaly a   (Euler density or logarithmic divergence on S^d$S^d$) coefficient for higher-derivative conformal higher spin field in d=4$d=4$ and shown that it matches the expression found in arXiv:1306.5242 by a “holographic” method from a ratio of massless higher spin determinants in AdS₅. Here we repeat the same computation in on 6-sphere and demonstrate that the result matches again the one following from AdS₇. We also discuss explicitly similar matching in the d=2$d=2$ case.     

Eikonal contributions to ultra high energy neutrino–nucleon cross sections in low scale gravity models

We calculate low scale gravity effects on the cross section for neutrino–nucleon scattering at center of mass energies up to the Greisen–Zatsepin–Kuzmin (GZK) scale, in the eikonal approximation. We compare the cases of an infinitely thin brane embedded in n=5$n=5$ compactified extra-dimensions, and of a brane with a physical tension MS=1 TeV$M_S=1\text{TeV}$ and MS=10 TeV$M_S=10\text{TeV}$. The extra dimensional Planck scale MD$M_D$ is set at ¹⁰³ GeV${10}^3\text{GeV}$ and 2×¹⁰³ GeV$2\times {10}^3\text{GeV}$. We also compare our calculations with neutral current standard model calculations in the same energy range, and compare the thin brane eikonal cross section to its saddle point approximation. New physics effects enhance the cross section by orders of magnitude on average. They are quite sensitive to MS$M_S$ and MD$M_D$ choices, though much less sensitive to n.     

On matrix geometry and effective actions

We provide an elementary systematic discussion of single-trace matrix actions and of the group of matrix reparameterization that acts on them. The action of this group yields a generalized notion of gauge invariance which encompasses ordinary diffeomorphism and gauge invariances. We apply the formalism to non-abelian D-brane actions in arbitrary supergravity backgrounds, providing in particular explicit checks of the consistency of Myers? formulas with supergravity gauge invariances. We also draw interesting consequences for emergent space models based on the study of matrix effective actions. For example, in the case of the _AdS5×S⁵${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ background, we explain how the standard tensor transformation laws of the supergravity fields under ordinary diffeomorphisms emerge from the D-instanton effective action in this background.     

Chaotic inflation,radiative corrections and precision cosmology

We employ chaotic (?²${?}^2$ and ?⁴${?}^4$) inflation to illustrate the important role radiative corrections can play during the inflationary phase. Yukawa interactions of ?  , in particular, lead to corrections of the form −κ?⁴ln(?/μ)$-\kappa {?}^4\ln (?/\mu )$, where κ>0$\kappa >0$ and μ   is a renormalization scale. For instance, ?⁴${?}^4$ chaotic inflation with radiative corrections looks compatible with the most recent WMAP (5 year) analysis, in sharp contrast to the tree level case. We obtain the 95% confidence limits 2.4×¹⁰⁻¹⁴?κ?5.7×¹⁰⁻¹⁴$2.4\times {10}^{\mathrm{-14}}?\kappa ?5.7\times {10}^{\mathrm{-14}}$, 0.931?ns?0.958$0.931?n_s?0.958$ and 0.038?r?0.205$0.038?r?0.205$, where ns$n_s$ and r   respectively denote the scalar spectral index and scalar to tensor ratio. The limits for ?²${?}^2$ inflation are κ?7.7×¹⁰⁻¹⁵$\kappa ?7.7\times {10}^{\mathrm{-15}}$, 0.929?ns?0.966$0.929?n_s?0.966$ and 0.023?r?0.135$0.023?r?0.135$. The next round of precision experiments should provide a more stringent test of realistic chaotic ?²${?}^2$ and ?⁴${?}^4$ inflation.     

O-BTZ: Orientifolded BTZ black hole

Banados–Teitelboim–Zanelli (BTZ) black holes are constructed by orbifolding AdS₃ geometry by boost transformations of its O(2,2)$O(2,2)$ isometry group. Here we construct a new class of solutions to AdS₃ Einstein gravity, orientifolded BTZ or O-BTZ   for short, which in general, besides the usual BTZ orbifolding, involve orbifolding (orientifolding) by a Z₂${\mathbb{Z}}_2$ part of O(2,2)$O(2,2)$ isometry group. This Z₂${\mathbb{Z}}_2$ is chosen such that it changes the orientation on AdS₃ while keeping the orientation on its 2D conformal boundary. O-BTZ solutions exhaust all un-oriented AdS₃ black hole solutions, as BTZ black holes constitute all oriented AdS₃ black holes. O-BTZ, similarly to BTZ black holes, are stationary, axisymmetric asymptotically AdS₃ geometries with two asymptotic charges, mass and angular momentum.