We study the holographic representation of the entanglement entropy, recently proposed by Ryu and Takayanagi, in a braneworld context. The holographic entanglement entropy of a de Sitter brane embedded in an anti–de Sitter (AdS) spacetime is evaluated using geometric quantities, and it is compared with two kinds of de Sitter entropy: a quarter of the area of the cosmological horizon on the brane and entropy calculated from the Euclidean path integral. We show that the three entropies coincide with each other in a certain limit. Remarkably, the entropy obtained from the Euclidean path integral is in precise agreement with the holographic entanglement entropy in all dimensions. We also comment on the case of a five-dimensional braneworld model with the Gauss-Bonnet term in the bulk.

We study the spectrum of loops as a part of a complete network of cosmic strings in flat spacetime. After a long transient regime, characterized by production of small loops at the scale of the initial conditions, it appears that a true scaling regime takes over. In this final regime the characteristic length of loops scales as $0.1t$, in contrast to earlier simulations which found tiny loops. We expect the expanding-universe behavior to be qualitatively similar. If this expectation is correct, then the large loop sizes have important cosmological implications. In particular, the nucleosynthesis bound then becomes $G\mu \lesssim {10}^{-7}$, much tighter than that obtained from earlier analyses.

We investigate the origin of Abelian and non-Abelian type magnetic instabilities induced by the Fermi surface mismatch between the two pairing fermions in a nonrelativistic model. The Abelian type instability occurs only in a gapless state and the Meissner mass squared becomes divergent at the gapless-gapped transition point, while the non-Abelian type instability happens in both gapless and gapped states and the divergence vanishes. The non-Abelian type instability can be cured in a strong coupling region.

The possibility of cancellation between different contributions to $d_e$, $d_n$ and $d_{\mathrm{Hg}}$ is reconsidered with special emphasis on the region that is phenomenologically interesting (intermediate values of $\tan \beta$ and sub-TeV sfermion masses). It is found that in the range favored by electroweak baryogenesis (i.e., $|\mu |\simeq M_1$ or $|\mu |\simeq M_2$), $\sin [{\theta }_{\mu }+{\theta }_{M_1}]\sim 1$ can be compatible with the EDM bounds even for slepton masses below 500 GeV. Such large values of the phases promise a successful electroweak baryogenesis. The possibility of large $CP$-odd effects at linear collider is also discussed.

We present a detailed calculation of the transition temperature in QCD with two light and one heavier (strange) quark mass on lattices with temporal extent $N_{\tau }=4$ and 6. Calculations with improved staggered fermions have been performed for various light to strange quark mass ratios in the range, $0.05\le {\widehat{m}}_l/{\widehat{m}}_s\le 0.5$, and with a strange quark mass fixed close to its physical value. From a combined extrapolation to the chiral (${\widehat{m}}_l\to 0$) and continuum ($aT\equiv 1/N_{\tau }\to 0$) limits we find for the transition temperature at the physical point $T_c{r}_0=0.457(7)$ where the scale is set by the Sommer-scale parameter $r_0$ defined as the distance in the static quark potential at which the slope takes on the value, $(\mathrm{d}{V}_{\overline{q}q}(r)/\mathrm{d}r{)}_{r=r_0}=1.65/r_0^2$. Using the currently best known value for $r_0$ this translates to a transition temperature $T_c=192(7)(4)\mathrm{MeV}$. The transition temperature in the chiral limit is about 3% smaller. We discuss current ambiguities in the determination of $T_c$ in physical units and also comment on the universal scaling behavior of thermodynamic quantities in the chiral limit.

The properties of the nonforward quark-quark correlation function are examined. We derive constraints on the correlation function from the transformation properties of the fundamental fields of QCD occurring in its definition. We further develop a method to construct an Ansatz for this correlator. We present the complete leading order set of generalized parton distributions in terms of the amplitudes of the Ansatz. Finally we conclude that the number of independent generalized parton helicity changing distributions is four.

We discuss the stability of strangelets by considering dynamical chiral symmetry breaking. For quark droplets of finite volume, we formulate the Nambu–Jona-Lasinio model with a basis set of the quark wave functions in the chiral bag model. Chiral symmetry breaking for the finite volume bag is discussed in a mean field approximation. Effects of the pion cloud including the chiral Casimir effect are investigated. Physical quantities of the quark droplets such as masses and radii are obtained for quark droplets of baryon numbers $A\le 5$. We also apply our model setting to the nucleon and discuss the stability of the quark droplets against nuclei.

We present an analysis of two-body $B$ decays with a pseudoscalar ($P$) and an axial-vector meson ($\mathcal{A}$) in the final state using factorization. We employ as inputs a limited number of experimental data, i.e. results for the $B\to K_1\gamma$, and $B\to K^{*}\gamma$ radiative decays and the branching ratios for $B\to \pi \rho$, $\pi K^{*}$, $K\rho$, $K\pi$ nonleptonic decays. In this way we are able to compare our predictions with recent data from the Belle and BABAR collaborations on $B\to a_1\pi$ and make predictions on several other $B\to P\mathcal{A}$ decay channels, which might be used as a guide for experimental researches and as tests of factorization.

The anarchic Randall-Sundrum model of flavor is a low energy solution to both the electroweak hierarchy and flavor problems. Such models have a warped, compact extra dimension with the standard model fermions and gauge bosons living in the bulk, and the Higgs living on or near the TeV brane. In this paper we consider bounds on these models set by lepton flavor-violation constraints. We find that loop-induced decays of the form $l\to l^{\prime }\gamma$ are ultraviolet sensitive and incalculable when the Higgs field is localized on a four-dimensional brane; this drawback does not occur when the Higgs field propagates in the full five-dimensional space-time. We find constraints at the few TeV level throughout the natural range of parameters, arising from $\mu -e$ conversion in the presence of nuclei, rare $\mu$ decays, and rare $\tau$ decays. A tension exists between loop-induced dipole decays such as $\mu \to e\gamma$ and tree-level processes such as $\mu -e$ conversion; they have opposite dependences on the five-dimensional Yukawa couplings, making it difficult to decouple flavor-violating effects. We emphasize the importance of the future experiments MEG and PRIME. These experiments will definitively test the Randall-Sundrum geometric origin of hierarchies in the lepton sector at the TeV scale.

We formulate the Hopf algebra underlying the $\mathfrak{s}\mathfrak{u}(2|2)$ world sheet $S$-matrix of the ${\mathrm{AdS}}_5\times S^5$ string in the AdS/CFT correspondence. For this we extend the previous construction in the $\mathfrak{s}\mathfrak{u}(1|2)$ subsector due to Janik to the full algebra by specifying the action of the coproduct and the antipode on the remaining generators. The nontriviality of the coproduct is determined by length-changing effects and results in an unusual central braiding. As an application we explicitly determine the antiparticle representation by means of the established antipode.

We relate bulk fields in Randall-Sundrum ${\mathrm{AdS}}_5$ phenomenological models to the world-volume fields of probe D7 branes in the Klebanov-Witten background of type IIB string theory. The string constructions are described by ${\mathrm{AdS}}_5\times T^{1,1}$ in their near-horizon geometry, with $T^{1,1}$ a 5d compact internal manifold that yields $\mathcal{N}=1$ supersymmetry in the dual 4d gauge theory. The effective 5d Lagrangian description derived from the explicit string construction leads to additional features that are not usually encountered in phenomenological model building.

The influence of vector backgrounds with restored Lorentz invariance on non-Abelian gauge field theories is studied. Lorentz invariance is ensured by taking the average over a Lorentz invariant ensemble of background vectors, which are shifting the gauge field. Thereby the propagation of fermions is suppressed over long distances. Contrary to the fermionic sector, pure gauge configurations of the background suppress the long-distance propagation of the bosons only partially, that is not in all channels beyond the leading contribution for a large number of colors.

Counting of microscopic states of black holes is performed within the framework of loop quantum gravity. This is the first calculation of the pure horizon states using statistical methods, which reveals the possibility of additional states missed in the earlier calculations, leading to an increase of entropy. Also for the first time a microcanonical temperature is introduced within the framework.

We investigate cosmological evolution and implications of cosmic strings with time-dependent tension. We derive basic equations of time development of the correlation length and the velocity of such strings, based on the one-scale model. Then, we find that, in the case where the tension depends on some power of the cosmic time, cosmic strings with time-dependent tension goes into the scaling solution if the power is lower than a critical value. We also discuss cosmic microwave background anisotropy and matter power spectra produced by these strings. The constraints on their tensions from the Wilkinson microwave anisotropy probe (WMAP) 3 yr data and Sloan digital sky survey (SDSS) data are also given.

We discuss how the baryon acoustic oscillation (BAO) signatures in the galaxy power spectrum can distinguish between modified gravity and the cosmological constant as the source of cosmic acceleration. To this end we consider a model characterized by a parameter $n$, which corresponds to the Dvali-Gabadadze-Porrati (DGP) model if $n=2$ and reduces to the standard spatially flat cosmological constant concordance model for $n$ equal to infinity. We find that the different expansion histories of the modified gravity models systematically shifts the peak positions of BAO. A preliminary analysis using the current SDSS luminous red galaxy (LRG) sample indicates that the original DGP model is disfavored unless the matter density parameter exceeds 0.3. The constraints will be strongly tightened with future spectroscopic samples of galaxies at high redshifts. We demonstrate that WFMOS, in collaboration with other surveys such as Planck, will powerfully constrain modified gravity alternatives to dark energy as the explanation of cosmic acceleration.

The equation of state (EOS) in quartessence models interpolates between two stages: $p\simeq 0$ at high energy densities and $p\approx -\rho$ at small ones. In the quartessence models analyzed up to now, the EOS is convex, implying increasing adiabatic sound speed ($c_s^2$) as the energy density decreases in an expanding universe. A nonnegligible $c_s^2$ at recent times is the source of the matter power spectrum problem that plagued all convex (nonsilent) quartessence models. Viability for these cosmologies is only possible in the limit of almost perfect mimicry to $\Lambda \mathrm{CDM}$. In this work we investigate if similarity to $\Lambda \mathrm{CDM}$ is also required in the class of quartessence models whose EOS changes concavity as the Universe evolves. We focus our analysis in the simple case in which the EOS has a steplike shape, such that at very early times $p\simeq 0$, and at late times $p\simeq \mathrm{const}<0$. For this class of models a nonnegligible $c_s^2$ is a transient phenomenon and could be relevant only at a more early epoch. We show that agreement with a large set of cosmological data requires that the transition between these two asymptotic states would have occurred at high redshift ($z_t\gtrsim 38$). This leads us to conjecture that the cosmic expansion history of any successful nonsilent quartessence is (practically) identical to the $\Lambda \mathrm{CDM}$ one.

The observed violation of $A_{CP}(B^0\to K^{+}{\pi }^{-})=A_{CP}(B^{+}\to K^{+}{\pi }^0)$ has been recently mentioned as a puzzle for the standard model. We point out that while this violation may be accounted for by a large color-suppressed tree amplitude, a sum rule involving three or four $B\to K\pi$ $CP$ asymmetries should hold. The current experimental status of these sum rules and of a sum rule for $B\to K\pi$ decay rates is presented.

We study the embedded QCD monopoles (“quark monopoles”) using low-lying eigenmodes of the overlap Dirac operator in zero- and finite-temperature SU(2) Yang-Mills theory on the lattice. These monopoles correspond to the gauge-invariant hedgehogs in the quark-antiquark condensates. The monopoles were suggested to be agents of the chiral symmetry restoration since their cores should suppress the chiral condensate. We study numerically the scalar, axial, and chirally invariant definitions of the embedded monopoles and show that the monopole densities are in fact globally anticorrelated with the density of the Dirac eigenmodes. We observe that the embedded monopoles corresponding to low-lying Dirac eigenvalues are dense in the chirally invariant (high temperature) phase and dilute in the chirally broken (low-temperature) phase. We find that the scaling of the scalar and axial monopole densities towards the continuum limit is similar to the scaling of the stringlike objects while the chirally invariant monopoles scale as membranes. The excess of gluon energy at monopole positions reveals that the embedded QCD monopole possesses a gluonic core which is, however, empty at the very center of the monopole.

Following searches for photinos and very light gravitinos in invisible decays of $\psi$ and ${\rm Y}$, we discuss new limits on Light Dark Matter and $U$ bosons, from $\psi$ and ${\rm Y}$ decays, as well as rare decays of $K^{+}$ and invisible decays of $\pi °$, $\eta$ and ${\eta }^{\prime }\dots$. The new limits involving the vector couplings of the $U$ to quarks turn out, not surprisingly, to be much less restrictive than existing ones on axial couplings, from an axionlike behavior of a light $U$ boson, tested in $\psi \to \gamma U$, ${\rm Y}\to \gamma U$ and $K^{+}\to {\pi }^{+}U$ decays (or as compared to the limit from parity-violation in atomic physics, in the presence of an axial coupling to the electron). Altogether the hypothesis of light $U$ bosons, and light dark matter particles, remains compatible with particle physics constraints, while allowing for the appropriate annihilation cross sections required, both at freeze-out (for the relic abundance) and nowadays (if $e^{+}$ from LDM annihilations are at the origin of the 511 keV line from the galactic bulge).

We present results for Wilson loops in strongly coupled gauge theories. The loops may be taken around an arbitrarily shaped contour and in any field theory with a dual IIB geometry of the form $M\times S^5$. No assumptions about supersymmetry are made. The first result uses D5 branes to show how the loop in any antisymmetric representation is computed in terms of the loop in the fundamental representation. The second result uses D3 branes to observe that each loop defines a rich sequence of operators associated with minimal surfaces in $S^5$. The action of these configurations are all computable. Both results have features suggesting a connection with integrability.