We calculate the nucleon strangeness $y_N$ in the chiral quark model and the meson cloud model. With the internal relation between the sigma term of $\pi N$ (${\sigma }_{\pi N}$) and $y_N$, we present the results of ${\sigma }_{\pi N}$ in these two models. Our calculations show that $y_N$ from the chiral quark model is significantly larger than that from the meson cloud model, whereas the difference of ${\sigma }_{\pi N}$ between the two models is relatively small. We also present the results of ${\sigma }_{KN}$ and ${\sigma }_{\eta N}$, which could be determined by ${\sigma }_{\pi N}$ and $y_N$ from their definition in the current algebra, and find that these two physical parameters are quite sensitive to $y_N$. The results indicate the necessity to restrict the parameters of the two models from more precision measurements.

We search for decays of a $B$ meson into a neutral $D$ meson and a charged kaon, with the $D$ meson decaying into a charged kaon, a charged pion, and a neutral pion. This final state can be reached through the $b\to c$ transition $B^{-}\to D^0{K}^{-}$ followed by the doubly Cabibbo-suppressed $D^0\to K^{+}{\pi }^{-}{\pi }^0$, or the $b\to u$ transition $B^{-}\to {\overline{D}}^0{K}^{-}$ followed by the Cabibbo-favored ${\overline{D}}^0\to K^{+}{\pi }^{-}{\pi }^0$. The interference of these two amplitudes is sensitive to the angle $\gamma$ of the unitarity triangle. We present results based on $226\times {10}^6$ $e^{+}{e}^{-}\to {\rm Y}(4S)\to B\overline{B}$ events collected with the BABAR detector at SLAC. We find no significant evidence for these decays and we set a limit $R_{\mathrm{ADS}}\equiv \frac{\Gamma ([K^{+}{\pi }^{-}{\pi }^0{]}_D{K}^{-})+\Gamma ([K^{-}{\pi }^{+}{\pi }^0{]}_D{K}^{+})}{\Gamma ([K^{+}{\pi }^{-}{\pi }^0{]}_D{K}^{+})+\Gamma ([K^{-}{\pi }^{+}{\pi }^0{]}_D{K}^{-})}<0.039$ at 95% confidence level, which we translate with a Bayesian approach into $r_B\equiv |A(B^{-}\to {\overline{D}}^0{K}^{-})/A(B^{-}\to D^0{K}^{-})|<0.19$ at 95% confidence level.

Modification of standard big-bang nucleosynthesis is considered in the minimal supersymmetric standard model to resolve the excessive theoretical prediction of the abundance of primordial lithium 7. We focus on the stau as a next-lightest superparticle, which is long lived due to its small mass difference with the lightest superparticle. It provides a number of additional decay processes of ${}^7\mathrm{Li}$ and ${}^7\mathrm{Be}$. A particularly important process is the internal conversion in the stau-nucleus bound state, which destroys the ${}^7\mathrm{Li}$ and ${}^7\mathrm{Be}$ effectively. We show that the modification can lead to a prediction consistent with the observed abundance of ${}^7\mathrm{Li}$.

I derive an effective theory for dense, cold, and massive quark matter. To this end, I employ a general effective action formalism where antiquarks and quarks far from the Fermi surface, as well as hard gluons, are integrated out explicitly. I show that the resulting effective action depends crucially on the projectors used to separate quarks from antiquarks. If one neglects the quark masses in these projectors, the Feynman rules of the effective theory involve quark mass insertions which connect quark with antiquark propagators. Including the quark masses into these projectors, mass insertions do not appear and the Feynman rules are identical to those found in the zero-mass limit.

We investigate the phenomenology of the Randall-Sundrum (RS) radion in realistic models of electroweak symmetry breaking with bulk gauge and fermion fields, since the radion may turn out to be the lightest particle in such models. We calculate the coupling of the radion in such scenarios to bulk fermion and gauge modes. Special attention needs to be devoted to the coupling to massless gauge fields (photon, gluon), since it is well known that loop effects may be important for these fields. We also present a detailed explanation of these couplings from the conformal field theory interpretation. We then use these couplings to determine the radion branching fractions and discuss some of the discovery potential of the LHC for the radion. We find that the $\gamma \gamma$ signal is enhanced over most of the range of the radion mass over the $\gamma \gamma$ signal of a standard model Higgs boson, as long as the RS scale is sufficiently low. However, the signal significance depends strongly on free parameters that characterize the magnitude of bare brane-localized kinetic terms for the massless gauge fields. In the absence of such terms, the signal can be enhanced over the traditional RS1 models (where all standard model fields are localized on the IR brane), but the signal can also be reduced compared to RS1 if the brane-localized terms are sizeable. We also show that for larger radion masses, where the $\gamma \gamma$ signal is no longer significant, one can use the usual 4 lepton signal to discover the radion.

We investigate the effect of the bulk contents in the Dvali-Gabadadze-Porrati (DGP) braneworld on the evolution of the universe. We find that, although the pure DGP model cannot accommodate the transition of the effective equation of state of dark energy, once the bulk matter $T_5^5$ is considered, the modified model can realize the $w_{\mathrm{eff}}$ crossing $-1$. However, this transition of the equation of state cannot be realized by just considering bulk-brane energy exchange or the Gauss-Bonnet effect while the bulk matter contribution is not included. $T_5^5$ plays the major role in the modified DGP model to have the $w_{\mathrm{eff}}$ crossing $-1$ behavior. We show that our model can describe the superacceleration of our universe with the equation of state of the effective dark energy and the Hubble parameter in agreement with observations.

We investigate evolutional paths of an extended quintessence with a nonminimally coupled phantom scalar field $\psi$ to the Ricci curvature. The dynamical system methods are used to investigate typical regimes of dynamics at the late time. We demonstrate that there are two generic types of evolutional scenarios which approach the attractor (a focus or a node type critical point) in the phase space: the quasioscillatory and monotonic trajectories approach the attractor which represents the Friedmann-Robertson-Walker model with the cosmological constant. We demonstrate that the dynamical system admits an invariant two-dimensional submanifold and discuss that which cosmological scenario is realized depends on the behavior of the system on the phase plane $(\psi ,{\psi }^{\prime })$. We formulate simple conditions on the value of the coupling constant $\xi$ for which trajectories tend to the focus in the phase plane and hence damping oscillations around the mysterious value $w=-1$. We describe this condition in terms of slow-roll parameters calculated at the critical point. We discover that the generic trajectories in the focus-attractor scenario come from the unstable node. We also investigate the exact form of the parametrization of the equation of state parameter $w(z)$ (directly determined from dynamics) which assumes a different form for both scenarios.

We investigate the magnetic susceptibility of the QCD vacuum with the $1/N_c$ corrections taken into account, based on the instanton vacuum. Starting from the instanton liquid model, we derive the gauged light-quark partition function in the presence of the current quark mass as well as of external Abelian vector and tensor fields. We consider the $1/N_c$ meson-loop corrections which are shown to contribute to the magnetic susceptibility by around 15% for the up (and down) quarks. We also take into account the tensor terms of the quark-quark interaction from the instanton vacuum as well as the finite-width effects, both of which are of order $\mathcal{O}(1/N_c)$. The effects of the tensor terms and finite width turn out to be negligibly small. The final results for the up-quarks are given as: $\chi ⟨i{\psi }^{†}\psi {⟩}_0\simeq 35–40\mathrm{MeV}$ with the quark condensate $⟨i{\psi }^{†}\psi {⟩}_0$. We also discuss the pion mass dependence of the magnetic susceptibility in order to give a qualitative guideline for the chiral extrapolation of lattice data.

Higgs bosons with very suppressed couplings to fermions (“fermiophobic Higgs bosons,” $h_f$) can decay to two photons ($\gamma \gamma$) with a branching ratio significantly larger than that expected for the standard model Higgs boson for $m_{h_f}<150\mathrm{GeV}$. Such a particle would give a clear signal at the LHC and can arise in the two Higgs doublet model (type I) in which $h_f\to \gamma \gamma$ is mediated by $W^{\pm }$ and charged Higgs boson ($H^{\pm }$) loops. We show that the $H^{\pm }$ loops can cause both constructive and destructive contributions with a magnitude considerably larger than the anticipated precision in the measurement of the photonic decay channel at future hadron and lepton colliders.

Masses of tetraquarks with two heavy quarks and open charm and bottom are calculated in the framework of the diquark-antidiquark picture in the relativistic quark model. All model parameters were regarded as fixed by previous considerations of various properties of mesons and baryons. The light quarks and diquarks are treated completely relativistically. The $c$ quark is assumed to be heavy enough to make the diquark configurations dominating. The diquarks are considered not to be pointlike but to have an internal structure which is taken into account by the calculated diquark form factor entering the diquark-gluon interaction. It is found that all the $(cc)(\overline{q}{\overline{q}}^{\prime })$ tetraquarks have masses above the thresholds for decays into open charm mesons. Only the $I(J^P)=0(1^{+})$ state of $(bb)(\overline{u}\overline{d})$ lies below the $B{B}^{*}$ threshold and is predicted to be narrow.

Diffractive parton distributions of the proton are determined from fits to diffractive data from HERA. In addition to the twist-2 contribution, the twist-4 contribution from longitudinally polarized virtual photons is considered, which is important in the region of small diffractive masses. A new prediction for the longitudinal diffractive structure function is presented which differs significantly from that obtained in the pure twist-2 analyses.

We discuss combining gravitational lensing of galaxies and the cosmic microwave background by clusters to measure cosmographic distance ratios, and hence dark energy parameters. Advantages to using the cosmic microwave background as the second source plane, instead of galaxies, include a well-determined source distance, a longer lever arm for distance ratios, typically up to an order of magnitude higher sensitivity to dark energy parameters, and a decreased sensitivity to photometric redshift accuracy of the lens and galaxy sources. Disadvantages include higher statistical errors, potential systematic errors, and the need for disparate surveys that overlap on the sky. Ongoing and planned surveys, such as the South Pole Telescope in conjunction with the Dark Energy Survey, can potentially reach the statistical sensitivity to make interesting consistency tests of the standard cosmological constant model. Future measurements that reach 1% or better precision in the convergences can provide sharp tests for future supernovae distance measurements.

We use the non-normalizable complex deformations to describe the stringy realizations of the metastable vacua in $\mathcal{N}=1$, $SU(N_c)$ SUSY theories with $N_f>N_c$ massive fundamental flavors. The consideration of the non-normalizable deformations requires a modified toric duality. The new approach considers the tachyon condensation between pairs of wrapped D5 branes and anti-D5 branes and the resulting mixing between some cycles in the geometry. We enlarge the class of metastable vacua to the case of branes-antibranes wrapped on cycles of deformed $A_n$ singularities.

In this paper we analyze the vacuum polarization effects associated with a massless fermionic field in a higher-dimensional global monopole spacetime in the “braneworld” scenario. In this context we admit that our Universe, the bulk, is represented by a flat $(n-1)$-dimensional brane having a global monopole in an extra transverse three-dimensional submanifold. We explicitly calculate the renormalized vacuum average of the energy-momentum tensor, $⟨T_A^B(x){⟩}_{\mathrm{Ren}}$, admitting the global monopole as being a pointlike object. We observe that this quantity depends crucially on the value of $n$, and provide explicit expressions to it for specific values attributed to $n$.

We present an Ansatz for the planar five-loop four-point amplitude in maximally supersymmetric Yang-Mills theory in terms of loop integrals. This Ansatz exploits the recently observed correspondence between integrals with simple conformal properties and those found in the four-point amplitudes of the theory through four loops. We explain how to identify all such integrals systematically. We make use of generalized unitarity in both four and $D$ dimensions to determine the coefficients of each of these integrals in the amplitude. Maximal cuts, in which we cut all propagators of a given integral, are an especially effective means for determining these coefficients. The set of integrals and coefficients determined here will be useful for computing the five-loop cusp anomalous dimension of the theory which is of interest for nontrivial checks of the AdS/CFT duality conjecture. It will also be useful for checking a conjecture that the amplitudes have an iterative structure allowing for their all-loop resummation, whose link to a recent string-side computation by Alday and Maldacena opens a new venue for quantitative AdS/CFT comparisons.

Supernova remnants are likely to be the accelerators of the galactic cosmic rays. Assuming the correctness of this hypothesis, we develop a method to extract the parent cosmic ray spectrum from the very high energy gamma-ray flux emitted by supernova remnants (and other gamma transparent sources). Namely, we calculate semianalytically the (inverse) operator which relates an arbitrary gamma-ray flux to the parent cosmic ray spectrum, without relying on any theoretical assumption about the shape of the cosmic ray and/or photon spectrum. We illustrate the use of this technique by applying it to the young SNR RX J1713.7-3946 which has been observed by the High Energy Stereoscopic System (H.E.S.S.) experiment during the last three years. Specific implementations of the method permit using as an input either the parametrized very high energy gamma-ray flux or directly the raw data. The possibility to detect features in the cosmic rays spectrum and the error in the determination of the parent cosmic ray spectrum are also discussed.

In the dense-neutrino region at 50–400 km above the neutrino sphere in a supernova, neutrino-neutrino interactions cause large flavor transformations. We study when the multiangle nature of the neutrino trajectories leads to flavor decoherence between different angular modes. We consider a two-flavor mixing scenario between ${\nu }_e$ and another flavor ${\nu }_x$ and assume the usual hierarchy $F_{{\nu }_e}>F_{{\overline{\nu }}_e}>F_{{\nu }_x}=F_{{\overline{\nu }}_x}$ for the number fluxes. We define $ϵ=(F_{{\nu }_e}-F_{{\overline{\nu }}_e})/(F_{{\overline{\nu }}_e}-F_{{\overline{\nu }}_x})$ as a measure for the deleptonization flux which is the one crucial parameter. The transition between the quasi-single-angle behavior and multiangle decoherence is abrupt as a function of $ϵ$. For typical choices of other parameters, multiangle decoherence is suppressed for $ϵ\gtrsim 0.3$, but a much smaller asymmetry suffices if the neutrino mass hierarchy is normal and the mixing angle small. The critical $ϵ$ depends logarithmically on the neutrino luminosity. In a realistic supernova scenario, the deleptonization flux is probably enough to suppress multiangle decoherence.

We study the predictions of holographic QCD for various observable four-point quark-flavor current-current correlators. The dual 5-dimensional bulk theory we consider is a $SU(3{)}_L\times SU(3{)}_R$ Yang-Mills theory in a slice of $\mathrm{Ad}{\mathrm{S}}_5$ spacetime with boundaries. Particular UV and IR boundary conditions encode the spontaneous breaking of the dual 4D global chiral symmetry down to the $SU(3{)}_V$ subgroup. We explain in detail how to calculate the 4D four-point quark-flavor current-current correlators using the 5D holographic theory, including interactions. We use these results to investigate predictions of holographic QCD for the $\Delta I=1/2$ rule for kaon decays and the $B_K$ parameter. The results agree well in comparison with experimental data, with an accuracy of 25% or better. The holographic theory automatically includes the contributions of the meson resonances to the four-point correlators. The correlators agree well in the low-momentum and high-momentum limit, in comparison with chiral perturbation theory and perturbative QCD results, respectively.

Perturbative Coulomb gauge Yang-Mills theory within the first order formalism is considered. Using a differential equation technique and dimensional regularization, analytic results for both the ultraviolet divergent and finite parts of the two-point functions at one-loop order are derived. It is shown how the nonultraviolet divergent parts of the results are finite at spacelike momenta with kinematical singularities on the light-cone and subsequent branch cuts extending into the timelike region.

A class of $(n+1)$-dimensional $(n\ge 3)$ topological black hole solutions in Einstein-Maxwell-dilaton theory with Liouville-type potentials for the dilaton field is presented. In these spacetimes, the black hole horizon and the cosmological horizon can be an $(n-1)$-dimensional positive, zero, or negative constant curvature hypersurface. Because of the presence of the dilaton field, these topological black holes are neither asymptotically flat nor (anti–)de Sitter. We calculate the charge, mass, temperature, entropy, and electric potential of these solutions. We also analyze thermodynamics of these topological black holes and disclose the effect of the dilaton field on the thermal stability of the solutions.