We present a lattice QCD calculation of the low-energy constants of the leading order chiral Lagrangian. In these simulations the epsilon regime is reached by using tree-level improved nHYP Wilson fermions combined with reweighting in the quark mass. We analyze two point functions on two ensembles with lattices of size $(1.85\mathrm{fm}{)}^4$ and $(2.8\mathrm{fm}{)}^4$, and at several quark mass values between 4 and 20 MeV. The data are well fitted with next-to-leading order chiral perturbative formulas and predict $F=90(4)\mathrm{MeV}$ and ${\Sigma }^{1/3}=248(6)\mathrm{MeV}$ in the $\overline{\mathrm{MS}}$ scheme at 2 GeV.

Spontaneous $CP$ violation in the strong interaction is analyzed at $\theta =\pi$ within the framework of the two-flavor Nambu-Jona-Lasinio model. It is found that the occurrence of spontaneous $CP$ violation at $\theta =\pi$ depends on the strength of the ’t Hooft determinant interaction, which describes the effect of instanton interactions. The dependence of the phase structure, and, in particular, of the $CP$-violating phase, on the quark masses, temperature, baryon and isospin chemical potential is examined in detail. When available a comparison to earlier results from chiral perturbation theory is made. From our results we conclude that spontaneous $CP$ violation in the strong interaction is an inherently low-energy phenomenon. In all cases we find agreement with the Vafa-Witten theorem, also at nonzero density and temperature. Meson masses and mixing in the $CP$-violating phase display some unusual features as a function of instanton interaction strength. A modification of the condition for charged pion condensation at nonzero isospin chemical potential and a novel phase of charged $a_0$ mesons are discussed.

The lightcone formalism including SU(3) breaking effects for the light pseudoscalar mesons is studied using soft-collinear effective theory (SCET), where the conformal symmetries needed for the expansion can be clearly implemented. The lightcone distribution amplitudes (LCDAs) are well defined at each order in the SCET power counting, $\lambda$. Relations between the LCDAs are reproduced using the SCET formalism. Treating the SU(3) breaking perturbatively, the leading breaking effects can be described in a simple manner. As a result, a new relationship among the LCDAs for the light mesons $\pi$, $K$, and $\eta$ is developed, valid to leading order in the SU(3) breaking.

In this paper the processes $e^{+}{e}^{-}\to J/\Psi J/\Psi$, $J/\Psi {\psi }^{\prime }$, ${\psi }^{\prime }{\psi }^{\prime }$ are considered in the framework of light cone formalism. An important distinction of this approach in comparison to the approaches used in other papers is that relativistic and leading logarithmic radiative corrections to the cross section can be resummed within light cone formalism. In this paper, the effect of this resummation is studied. It is shown that this effect is important, especially for the production of higher charmonium mesons. The predicted cross sections are in agreement with the upper bounds set by the Belle Collaboration.

We study the effects of unparticle physics on muon $g-2$ and lepton flavor violating (LFV) tau decay processes. LFV interactions between the standard model sector and unparticles can explain the difference of the experimental value of muon $g-2$ from the standard model prediction. While the same couplings generate LFV tau decay, we found that LFV coupling can be of $\mathcal{O}(0.1\dots 1)$ without conflict with the experimental bounds of LFV tau decay if the scaling dimension of unparticle operator $d_{\mathcal{U}}\gtrsim 1.6$.

We report the first observation of $B^{\pm }\to \psi (2S){\pi }^{\pm }$, a Cabibbo- and color-suppressed decay. This analysis is based on $657\times {10}^6$ $B\overline{B}$ events collected at the ${\rm Y}(4S)$ resonance with the Belle detector at the KEKB energy-asymmetric $e^{+}{e}^{-}$ collider. The measured branching fraction is $(2.44\pm 0.22\pm 0.20)\times {10}^{-5}$ and the charge asymmetry is $\mathcal{A}=0.022\pm 0.085\pm 0.016$. The ratio of the branching fractions $\mathcal{B}(B^{\pm }\to \psi (2S){\pi }^{\pm })/\mathcal{B}(B^{\pm }\to \psi (2S)K^{\pm })=(3.99\pm 0.36\pm 0.17)\%$ is also determined.

We find a 16-supersymmetric mass-deformed Bagger-Lambert theory with $SO(4)\times SO(4)$ global $R$ symmetry. The $R$ charge plays the role of the noncentral term in the superalgebra. This theory has one symmetric vacuum and two inequivalent broken sectors of vacua. Each sector of the broken symmetry has $SO(4)$ geometry. We find the $1/2$ BPS domain walls connecting the symmetric phase and any broken phase, and $1/4$ BPS supertubelike objects, which may appear as anyonic $q$-balls in the symmetric phase or vortices in the broken phase. We also discuss mass deformations, which reduce the number of supersymmetries.

We calculate the area of a marginally trapped surface formed by a head-on collision of gravitational shock waves in ${\mathrm{AdS}}_D$. We use this to obtain a lower bound on the entropy produced after the collision. A comparison to entropy production in heavy-ion collisions is included. We also discuss an $O(D-2)$ remnant of conformal symmetry, which is present in a class of gravitational shockwave collisions in ${\mathrm{AdS}}_D$ and which might be approximately realized (with $D=5$) in central heavy-ion collisions.

We continue our study of the low energy implications of $M$ theory vacua on $G_2$-manifolds, undertaken in B. S. Acharya, K. Bobkov, G. L. Kane, P. Kumar, and J. Shao, Phys. Rev. D 76, 126010 (2007); B. Acharya, K. Bobkov, G. Kane, P. Kumar, and D. Vaman, Phys. Rev. Lett. 97, 191601 (2006), where it was shown that the moduli can be stabilized and a TeV scale generated, with the Planck scale as the only dimensionful input. A well-motivated phenomenological model, the $G_2$-MSSM, can be naturally defined within the above framework. In this paper, we study some of the important phenomenological features of the $G_2$-MSSM. In particular, the soft supersymmetry breaking parameters and the superpartner spectrum are computed. The $G_2$-MSSM generically gives rise to light gauginos and heavy scalars with wino lightest supersymmetric particles when one tunes the cosmological constant. Electroweak symmetry breaking is present but fine-tuned. The $G_2$-MSSM is also naturally consistent with precision gauge coupling unification. The phenomenological consequences for cosmology and collider physics of the $G_2$-MSSM will be reported in more detail soon.

We examine a double trace deformation of $SU(N)$ Yang-Mills theory which, for large $N$ and large volume, is equivalent to unmodified Yang-Mills theory up to $O(1/N^2)$ corrections. In contrast to the unmodified theory, large $N$ volume independence is valid in the deformed theory down to arbitrarily small volumes. The double trace deformation prevents the spontaneous breaking of center symmetry which would otherwise disrupt large $N$ volume independence in small volumes. For small values of $N$, if the theory is formulated on ${\mathbb{R}}^3\times S^1$ with a sufficiently small compactification size $L$, then an analytic treatment of the nonperturbative dynamics of the deformed theory is possible. In this regime, we show that the deformed Yang-Mills theory has a mass gap and exhibits linear confinement. Increasing the circumference $L$ or number of colors $N$ decreases the separation of scales on which the analytic treatment relies. However, there are no order parameters which distinguish the small and large radius regimes. Consequently, for small $N$ the deformed theory provides a novel example of a locally four-dimensional pure-gauge theory in which one has analytic control over confinement, while for large $N$ it provides a simple fully reduced model for Yang-Mills theory. The construction is easily generalized to QCD and other QCD-like theories.

An infinite family of axisymmetric charged dust disks of finite extension is presented. The disks are obtained by solving the vacuum Einstein-Maxwell equations for conformastatic spacetimes, which are characterized by only one metric function. In order to obtain the solutions, a functional relationship between the metric function and the electric potential is assumed. It is also assumed that the metric function is functionally dependent on another auxiliary function, which is taken as a solution of the Laplace equation. The solutions for the auxiliary function are then taken as given by the infinite family of generalized Kalnajs disks recently obtained by González and Reina [G. A. González and J. I. Reina, Mon. Not. R. Astron. Soc. 371, 1873 (2006).], expressed in terms of the oblate spheroidal coordinates and corresponding to a family of well-behaved Newtonian axisymmetric thin disks of finite radius. The obtained relativistic thin disks have a charge density that is equal, except maybe by a sign, to their mass density, in such a way that the electric and gravitational forces are in exact balance. The energy density of the disks is everywhere positive and well behaved, vanishing at the edge. Accordingly, as the disks are made of dust, their energy-momentum tensor agrees with all the energy conditions.

We study pocket universes which have zero cosmological constant and nontrivial boundary topology. These arise from bubble collisions in eternal inflation. Using a simplified dust model of collisions we find that boundaries of any genus can occur. Using a radiation shell model we perform analytic studies in the thin-wall limit to show the existence of geometries with a single toroidal boundary. We give plausibility arguments that higher genus boundaries can also occur. In geometries with one boundary of any genus a timelike observer can see the entire boundary. Geometries with multiple disconnected boundaries can also occur. In the spherical case with two boundaries the boundaries are separated by a horizon. Our results suggest that the holographic dual description for eternal inflation, proposed by Freivogel, Sekino, Susskind and Yeh, should include summation over the genus of the base space of the dual conformal field theory. We point out peculiarities of this genus expansion compared to the string perturbation series.

We investigate the impact of TeV-scale matter belonging to complete vectorlike multiplets of unified groups on the lightest Higgs boson in the MSSM. We find that consistent with perturbative unification and electroweak precision data the mass $m_h$ can be as large as 160 GeV. These extended MSSM models can also render the little hierarchy problem less severe, but only for lower values of $m_h(\lesssim 125)\mathrm{GeV}$. We present estimates for the sparticle mass spectrum in these models.

We present a calculation of the renormalization coefficients of the quark bilinear operators and the $K-\overline{K}$ mixing parameter $B_K$. The coefficients relating the bare lattice operators to those in the RI/MOM scheme are computed nonperturbatively and then matched perturbatively to the $\overline{\mathrm{MS}}$ scheme. The coefficients are calculated on the RBC/UKQCD $2+1$ flavor dynamical lattice configurations. Specifically we use a ${16}^3\times 32$ lattice volume, the Iwasaki gauge action at $\beta =2.13$ and domain wall fermions with $L_s=16$.

Recent experimental data on the radiative decays $B\to V\gamma$, where $V$ is a light vector meson, find small isospin violation in $B\to K^{*}\gamma$ while isospin asymmetries in $B\to \rho \gamma$ are of order 20%, with large uncertainties. Using soft-collinear effective theory, we calculate isospin asymmetries in these radiative $B$ decays up to $O(1/m_b)$, also including $O(v{\alpha }_s)$ contributions from nonperturbative charming penguins (NPCP). In the absence of NPCP contributions, the theoretical predictions for the asymmetries are a few percent or less. Including the NPCP can significantly increase the isospin asymmetries for both $B\to V\gamma$ modes. We also consider the effect of the NPCP on the branching ratio and $CP$ asymmetries in $B^{\pm }\to V^{\pm }\gamma$.

We study the optimization of a neutrino factory with respect to nonstandard neutral current neutrino interactions, and compare the results to those obtained without nonstandard interactions. We discuss the muon energy, baselines, and oscillation channels as degrees of freedom. Our conclusions are based on both analytical calculations and on a full numerical simulation of the neutrino factory setup proposed by the international design study (IDS-NF). We consider all possible nonstandard parameters, and include their complex phases. We identify the impact of the different parameters on the golden, silver, and disappearance channels. We come to the conclusion that, even in the presence of nonstandard interactions, the performance of the neutrino factory hardly profits from a silver channel detector, unless the muon energy is significantly increased compared to the IDS-NF setup. Apart from the dispensable silver channel detector, we demonstrate that the IDS-NF setup is close to optimal even if nonstandard interactions are considered. We find that one very long baseline is a key component in the search for nonstandard interactions, in particular, for $|{ϵ}_{\mu \tau }^m|$ and $|{ϵ}_{\tau \tau }^m|$.

Vacuum force is an interesting low energy test for brane worlds due to its dependence on field’s modes and its role in submillimeter gravity experiments. In this work, we generalize a previous model example: the scalar field vacuum force between two parallel plates lying in the brane of a Randall-Sundrum scenario extended by $p$ compact dimensions (RSII-$p$). Upon use of Green’s function technique, for the massless scalar field, the 4D force is obtained from a zero mode while leading order corrections due to the noncompact dimension turn out attractive and depend on the separation between plates as $l^{-(6+p)}$. For the massive scalar field, a quasilocalized mode yields the 4D force with attractive corrections behaving like $l^{-(10+p)}$. Corrections are negligible with respect to 4D force for anti-de Sitter (${\mathrm{AdS}}_{(5+p)}$) radius much less than $\sim {10}^{-6}\mathrm{m}$. In the massless case we also determined, numerically, the corrections due to compact dimensions. To avoid conflict with experimental data we get $R\le 0.4\mu \mathrm{m}$, $0.3\mu \mathrm{m}$ for the cases $p=1$, 2, respectively. Although the $p=0$ case is not physically viable due to the different behavior in regard to localization for the massless scalar and electromagnetic fields it yields a useful comparison between the dimensional regularization and Green’s function techniques as we describe in the discussion.

Upon applying Chamseddine’s noncommutative deformation of gravity, we obtain the leading order noncommutative corrections to the Robertson-Walker metric tensor. We get an isotropic inhomogeneous metric tensor for a certain choice of the noncommutativity parameters. Moreover, the singularity of the commutative metric at $t=0$ is replaced by a more involved space-time structure in the noncommutative theory. In a toy model we construct a scenario where there is no singularity at $t=0$ at leading order in the noncommutativity parameter. Although singularities may still be present for nonzero $t$, they need not be the source of all timelike geodesics and the result resembles a bouncing cosmology.

It has recently been shown that a stationary, asymptotically flat vacuum black hole in five space-time dimensions with two commuting axial symmetries must have an event horizon with either a spherical, ring or lens-space topology. In this paper, we study the third possibility, a so-called black lens with $L(n,1)$ horizon topology. Using the inverse scattering method, we construct a black-lens solution with the simplest possible rod structure, and possessing a single asymptotic angular momentum. Its properties are then analyzed; in particular, it is shown that there must either be a conical singularity or a naked curvature singularity present in the space-time.

We consider a Schwarzschild black hole immersed in a ghost condensate background. It is shown that the Hawking radiation in the quanta of small perturbations around this background is highly suppressed—in particular, it is not given by a thermal spectrum. This result is in accord with observations that such black holes can be used to violate the generalized second law of thermodynamics, and thus cannot have a standard entropy/area relation.