We give an example of modeling phenomenological heavy-quark potentials in a five-dimensional framework nowadays known as AdS/QCD. In particular we emphasize the absence of infrared renormalons.

We study the mass spectrum of the $q^3{\overline{q}}^3$ mesons both from the common $S$ wave quark model with colormagnetic interactions, and from the quark model with triquark correlations. Two cluster configurations $(q^3)-({\overline{q}}^3)$ and $(q^2\overline{q})-(q{\overline{q}}^2)$ are considered. In the spectrums of both models, we find rather stable states which have the same quantum numbers as the particle resonances which are corresponding to the $p\overline{p}$ enhancement, $p\overline{\Lambda }$ enhancement, and $\Lambda \overline{\Lambda }$ enhancement with spin-$\mathbf{0}$ or $\mathbf{1}$. This implies these enhancements are not experimental artifacts. The color-spin-flavor structures of $p\overline{p}$, $p\overline{\Lambda }$, and $\Lambda \overline{\Lambda }$ enhancements are revealed. It has been found that, if there exists quark correlation in the baryonium, the $p\overline{p}$ enhancement as a baryonium is mainly a state of $|{\mathbf{120}}_{cs},{\overline{\mathbf{6}}}_c,\mathbf{2},{\mathbf{3}}_f\oplus {\overline{\mathbf{6}}}_f⟩|{\overline{\mathbf{120}}}_{cs},{\mathbf{6}}_c,\mathbf{2},{\overline{\mathbf{3}}}_f\oplus {\mathbf{6}}_f⟩$ in the configuration $(q^2\overline{q})-(q{\overline{q}}^2)$, with few mixtures of $|{\mathbf{70}}_{cs},{\mathbf{8}}_c,\mathbf{2},{\mathbf{8}}_f⟩|{\overline{\mathbf{70}}}_{cs},{\mathbf{8}}_c,\mathbf{2},{\mathbf{8}}_f⟩$ in the configuration $(q^3)-({\overline{q}}^3)$, where the subscripts $cs$, $c$, and $f$ indicate colorspin, color, and flavor, respectively. The existence of spin-$\mathbf{1}$ $\Lambda \overline{\Lambda }$, $p\overline{\Lambda }$, $p\overline{p}$ enhancements is predicted.

The study of two-pseudoscalar and two-photon decays for the scalar meson nonet below 1 GeV is performed within an effective approach in which the scalar resonances are described as (Jaffe’s) tetraquark states. The dominant (fall apart decay) and the subdominant (one transverse gluon as intermediate state) decay amplitudes are systematically taken into account. The latter improves the agreement with the experimental data. Possible scenarios concerning the scalar-isoscalar mixing are discussed.

We analyze the fast-moving string in the magnetic Melvin field background and find that the associated effective Lagrangian of string sigma model describes the spin-chain model with external magnetic field. The spin vector in the spin chain has been properly deformed and is living on the deformed two-sphere or deformed two-dimensional hyperboloid, depending on the direction around which the string is spinning. We describe in detail the characters of spin deformation and, in particular, see that this is a general property for a string moving in a class of deformed background.

By applying Noether method to $\mathcal{N}=1$ local supersymmetry in 11 dimensions, we obtained two candidates of $R^4$ corrections to the supergravity. The bosonic parts of these two completely match with the results obtained by type IIA string perturbative calculations. We also obtained 13 parameters which relate only fermionic terms.

In this paper we study the noncommutative effects to the lepton spectrum from the decay of a polarized top quark. It is shown that the lowest contribution comes from the quadratic terms of the noncommutative parameter. The deviations from the standard model are significant for small values of the noncommutative characteristic scale. However, the charged lepton spin correlation coefficient has a remarkable deviation from the standard model from very low values of the noncommutative characteristic scale to 1 TeV.

Recently striking multiple relations have been found between pure state two- and three-qubit entanglement and extremal black holes in string theory. Here we add further mathematical similarities which can be both useful in string and quantum information theories. In particular, we show that finding the frozen values of the moduli in the calculation of the macroscopic black-hole entropy in the $STU$ model is related to finding the canonical form for a pure three-qubit entangled state defined by the dyonic charges. In this picture the extremization of the BPS mass with respect to moduli is connected to the problem of finding the optimal local distillation protocol of a GHZ state from an arbitrary three-qubit pure state. These results and a geometric classification of $STU$ black holes, BPS and non-BPS can be described in the elegant language of twistors. Finally an interesting connection between the black-hole entropy and the average real entanglement of formation is established.

We describe a solitonic solution-generating technique in the five-dimensional general relativity. Reducing the five-dimensional problem to the four-dimensional one, we can systematically obtain single-rotational axially symmetric vacuum solutions. Applying the technique for a simple seed solution, we have previously obtained the series of stationary solutions which includes the $S^2$-rotating black ring. We analyze the qualitative features of these solutions, e.g., conical singularities, closed timelike curves, and spacetime curvatures. We investigate the rod structures of seed and solitonic solutions. We examine the relation between the expressions of the metric in the prolate-spheroidal coordinates and in the $C$-metric coordinates.

This paper presents a quasilocal method of studying the physics of dynamical black holes in numerical simulations. This is done within the dynamical horizon framework, which extends the earlier work on isolated horizons to time-dependent situations. In particular: (i) We locate various kinds of marginal surfaces and study their time evolution. An important ingredient is the calculation of the signature of the horizon, which can be either spacelike, timelike, or null. (ii) We generalize the calculation of the black hole mass and angular momentum, which were previously defined for axisymmetric isolated horizons to dynamical situations. (iii) We calculate the source multipole moments of the black hole which can be used to verify that the black hole settles down to a Kerr solution. (iv) We also study the fluxes of energy crossing the horizon, which describes how a black hole grows as it accretes matter and/or radiation. We describe our numerical implementation of these concepts and apply them to three specific test cases, namely, the axisymmetric head-on collision of two black holes, the axisymmetric collapse of a neutron star, and a nonaxisymmetric black hole collision with nonzero initial orbital angular momentum.

There is mounting observational evidence that the expansion of our Universe is undergoing a late-time acceleration. Among many proposals to describe this phenomenon, the cosmological constant ($\Lambda$) seems to be the simplest and the most natural explanation. However, despite its observational successes, such a possibility exacerbates the well known $\Lambda$ problem, requiring a natural explanation for its small, but nonzero, value. In this paper we consider a cosmological scenario driven by a varying cosmological term, in which the vacuum energy density decays linearly with the Hubble parameter, $\Lambda \propto H$. We show that this $\Lambda (t)\mathrm{CDM}$ model is indistinguishable from the standard one ($\Lambda \mathrm{CDM}$) in that the early radiation phase is followed by a long dust-dominated era, and only recently the varying $\Lambda$ term becomes dominant, accelerating the cosmic expansion. In order to test the viability of this scenario, we have used the most recent type Ia supernova data, i.e., the High-Z SN Search Team and the Supernova Legacy Survey (SNLS) Collaboration data. In particular, for the SNLS sample we have found $0.27\le {\Omega }_{\mathrm{m}}\le 0.37$ and $0.68\le H_0\le 0.72$ (at $2\sigma$), which is in good agreement with the currently accepted estimates for these parameters.

A heavy scalar field such as moduli or an inflaton generally mixes with a field responsible for the supersymmetry breaking. We study the scalar decay into the standard model particles and their superpartners, gravitinos, and the supersymmetry-breaking sector, particularly paying attention to decay modes that proceed via the mixing between the scalar and the supersymmetry-breaking field. The impacts of the new decay processes on cosmological scenarios are also discussed; the modulus field generically produces too many gravitinos, and most of the inflation models tend to result in too high reheating temperature and/or gravitino overproduction.

In the most general two-Higgs-doublet model (2HDM), there is no distinction between the two complex hypercharge-one $\mathrm{SU}(2{)}_{\mathrm{L}}$ doublet scalar fields, ${\Phi }_a$ $(a=1,2)$. Thus, any two orthonormal linear combinations of these two fields can serve as a basis for the Lagrangian. All physical observables of the model must be basis-independent. For example, $\tan \beta \equiv ⟨{\Phi }_2^0⟩/⟨{\Phi }_1^0⟩$ is basis-dependent and thus cannot be a physical parameter of the model. In this paper, we provide a basis-independent treatment of the Higgs sector with particular attention to the neutral Higgs boson mass-eigenstates, which generically are not eigenstates of $CP$. We then demonstrate that all physical Higgs couplings are indeed independent of $\tan \beta$. In specialized versions of the 2HDM, $\tan \beta$ can be promoted to a physical parameter of the Higgs-fermion interactions. In the most general 2HDM, the Higgs-fermion couplings can be expressed in terms of a number of physical “$\tan \beta$-like” parameters that are manifestly basis-independent. The minimal supersymmetric extension of the standard model provides a simple framework for exhibiting such effects.

We study the bulk mass effects on the electroweak phase transition at finite temperature in a five-dimensional $SU(3)$ gauge-Higgs unification model on an orbifold. We investigate whether the Higgs mass satisfying the experimental lower bound can be compatible with the strong first order phase transition necessary for a successful electroweak baryogenesis. Our numerical results show that the above statement can be realized by matter with bulk mass yielding a viable Higgs mass. We also find an interesting case where the heavier Higgs gives the stronger first order phase transition.

Uncertainty in the perturbative quantum chromodynamics (PQCD) calculation of $B$ decays is investigated in $B\to \pi$, $B\to D$ transition form factors and $B\to D\pi$ decay amplitudes. $B$-meson distribution amplitude dependence is studied by taking three kinds of distribution amplitudes suggested so far. It is found that almost the same $q^2$ dependence of the form factors can be obtained irrespective of the types of the $B$-meson distribution amplitudes by suitably choosing one parameter. The $B\to D\pi$ process shows the difference due to the distribution amplitude. The effect of the subleading component of the $B$-meson distribution amplitude is also studied in the three processes. The numerical results of calculations with the subleading component can be well approximated by the leading-order calculation with a suitable choice of the distribution amplitude parameters.

Nonlinear effects in hadronic interactions are treated by means of enhanced Pomeron diagrams, assuming that Pomeron-Pomeron coupling is dominated by soft partonic processes. It is shown that the approach allows to resolve a seeming contradiction between realistic parton momentum distributions, measured in deep inelastic scattering experiments, and the energy behavior of total proton-proton cross section. Also a general consistency with both soft and hard diffraction data is demonstrated. An important feature of the proposed scheme is that the contribution of semihard processes to the interaction eikonal contains a significant nonfactorizable part. On the other hand, the approach preserves the QCD factorization picture for inclusive high-$p_t$ jet production.

Lattice simulation data on the critical temperature and long-distance potential, that probe the degrees of freedom of the QCD string, are critically reviewed. It is emphasized that comparison of experimental or $SU(N_c)$ lattice data, at finite number of colors $N_c$, with free string theory can be misleading due to string interactions. Large-$N_c$ extrapolation of pure lattice gauge theory data, in both 3 and 4 dimensions, indicates that there are more world sheet degrees of freedom than the purely massless transverse ones of the free Nambu-Goto string. The extra variables are consistent with massive modes of oscillation that effectively contribute like $c\approx 1/2$ conformal degrees of freedom to highly excited states. As a concrete example, the highly excited spectrum of the Chodos-Thorn relativistic string in $1+1$ dimensions is analyzed, where there are no transverse oscillations. We find that the asymptotic density of states for this model is characteristic of a $c=1/2$ conformal world sheet theory. The observations made here should also constrain the backgrounds of holographic string models for QCD.

$B_s-{\overline{B}}_s$ mixing has been measured recently by D0 and CDF. The range predicted in the standard model is consistent with data. However, the standard model central values for $\Delta M_{B_s}$ and also $\Delta M_{B_d}$ are away from the data which may be indications of new physics. Using the observed values of $\Delta M_{B_s}$ and $\Delta M_{B_d}$ we study general constraints on flavor changing $Z^{\prime }$ interactions. In models with nonuniversal $Z^{\prime }$ couplings we find that significant enhancements over the standard model are still possible in the rare decay modes $B\to X_s{\tau }^{+}{\tau }^{-}$, $B\to X_s\nu \overline{\nu }$ and $B_s\to {\tau }^{+}{\tau }^{-}$. Tree-level $Z^{\prime }$ contributions to $K\to \pi \nu \overline{\nu }$ are now constrained to be very small, but one-loop effects can still enhance the standard model rate by a factor of 2.

The NuTeV experiment at Fermilab has obtained a unique high-statistics sample of neutrino and antineutrino interactions using its high-energy sign-selected beam. We present a measurement of the differential cross section for charged-current neutrino and antineutrino scattering from iron. We determine the relative $\overline{\nu }$ to $\nu$ cross section, $r={\sigma }^{\overline{\nu }}/{\sigma }^{\nu }$, at high energy with errors a factor of 2 smaller than the previous world average. Structure functions, $F_2(x,Q^2)$ and $x{F}_3(x,Q^2)$, are determined by fitting the inelasticity, $y$, dependence of the cross sections. This measurement has significantly improved systematic precision as a consequence of more precise understanding of hadron and muon energy scales.