Building on general formulas obtained from the approximate renormalized effective action, the stress-energy tensor of the quantized massive spinor and vector fields in the spacetime of the regular black hole is constructed. Such a black hole is the solution to the coupled system of nonlinear electrodynamics and general relativity. A detailed analytical and numerical analysis of the stress-energy tensor in the exterior region is presented. It is shown that for small values of the charge as well as large distances from the black hole the leading behavior of the stress-energy tensor is similar to that in the Reissner-Nordström geometry. Important differences appear when the inner horizon becomes close to the event horizon. A special emphasis is put on the extremal configuration and it is shown that the stress-energy tensor is regular inside the event horizon of the extremal black hole.

I discuss a mechanism which generates a mass term for a scalar field in an expanding universe. The mass of this field turns out to be generated by the cosmological constant and can be naturally small if protected by a conformal symmetry which is, however, broken in the gravitational sector. The mass is comparable today to the Hubble time. This scalar field could thus impact our Universe today and, for example, be at the origin of a time variation of the couplings and masses of the parameters of the standard model.

Recently proposed theories based on the cosmic presence of a vectorial field are compared and contrasted. In particular the so-called Einstein æther theory is discussed in parallel with a recent proposal of a strained space-time theory (cosmic defect theory). We show that the latter fits reasonably well the cosmic observed data with only one, or at most two, adjustable parameters, while other vector theories use much more. The Newtonian limits are also compared. Finally we show that the cosmic defect theory may be considered as a special case of the æther theories, corresponding to a more compact and consistent paradigm.

New physics at the weak scale that can couple to quarks typically gives rise to unacceptably large flavor changing neutral currents. An attractive way to avoid this problem is to impose the principle of minimal flavor violation. Recently it was noted that in minimal flavor violation only scalars with the same gauge quantum numbers as the standard model Higgs doublet or color octet scalars with the same weak quantum numbers as the Higgs doublet can couple to quarks. In this paper we compute the one-loop rate for production of a single color octet scalar through gluon fusion at the LHC, which can become greater than the tree level pair production rate for octet scalar masses around a TeV. We also calculate the precision electroweak constraint from $Z\to \overline{b}b$; this constraint on color octet mass and Yukawa coupling affects the allowed range for single octet scalar production through gluon fusion.

In this paper, we propose three different strategies to extract the weak mixing angle ${\varphi }_s$ of the $B_s$ system using penguin-mediated decays into vectors, mainly $B_s\to K^{*0}{\overline{K}}^{*0}$, $B_s\to \varphi {\overline{K}}^{*0}$, and $B_s\to \varphi \varphi$. We also provide predictions for the longitudinal branching ratio and $CP$ asymmetries of $B_s\to K^{*0}{\overline{K}}^{*0}$ using a method that combines QCD factorization with flavor symmetries to relate this decay to its $B_d$ counterpart.

A procedure is developed for using soft collinear effective theory (SCET) to generate fully exclusive events, which can then be compared to data from collider experiments. We show that SCET smoothly interpolates between QCD for hard emissions, and the parton shower for soft emissions, while resumming all large logarithms. In SCET, logarithms are resummed using the renormalization group, instead of classical Sudakov factors, so subleading logarithms can be resummed as well. In addition, all loop effects of QCD can be reproduced in SCET, which allows the effective theory to incorporate next-to-leading and higher-order effects. We also show through SCET that in the soft/collinear limit, successive branchings factorize, a fact which is essential to parton showers, and that the splitting functions of QCD are reproduced. Finally, combining these results, we present an example of an algorithm that incorporates the SCET results into an event generator which is systematically improvable.

We present measurements of decay matrix elements for hadronic transitions of the form ${\rm Y}(nS)\to {\rm Y}(mS)\pi \pi$, where $(n,m)=(3,1),(2,1),(3,2)$. We reconstruct charged and neutral pion modes with the final state Upsilon decaying to either ${\mu }^{+}{\mu }^{-}$ or $e^{+}{e}^{-}$. Dalitz plot distributions for the 12 decay modes are fit individually as well as jointly assuming isospin symmetry, thereby measuring the matrix elements of the decay amplitude. We observe and account for the anomaly previously noted in the dipion invariant mass distribution for the ${\rm Y}(3S)\to {\rm Y}(1S)\pi \pi$ transition and obtain good descriptions of the dynamics of the decay using the most general decay amplitude allowed by partial conservation of the axial-vector current considerations. The fits further indicate that the ${\rm Y}(2S)\to {\rm Y}(1S)\pi \pi$ and ${\rm Y}(3S)\to {\rm Y}(2S)\pi \pi$ transitions also show the presence of terms in the decay amplitude that were previously ignored, although at a relatively suppressed level.

We consider a model with a toroidally compactified extra dimension giving rise to a temperature-dependent 4D effective potential with one-loop contributions due to the Casimir effect, along with a 5D cosmological constant. The forms of the effective potential at low and high temperatures indicate a possibility for the formation of a domain wall bubble, formed by the modulus scalar field, surrounding an evaporating black hole. This is viewed as an example of a recently proposed black hole vacuum bubble arising from matter-sourced moduli fields in the vicinity of an evaporating black hole [D. Green, E. Silverstein, and D. Starr, Phys. Rev. D 74, 024004 (2006)]. The black hole bubble can be highly opaque to lower-energy particles and photons, and thereby entrap them within. For high-temperature black holes, there may also be a symmetry-breaking black hole bubble of false vacuum of the type previously conjectured by Moss [I. G. Moss, Phys. Rev. D 32, 1333 (1985)], tending to reflect low-energy particles from its wall. A double bubble composed of these two different types of bubble may form around the black hole, altering the hole’s emission spectrum that reaches outside observers. Smaller mass black holes that have already evaporated away could have left vacuum bubbles behind that contribute to the dark matter.

We apply a singularity-resolution technique utilized in loop quantum gravity to the polymer representation of quantum mechanics on $\mathbb{R}$ with the singular $-1/|x|$ potential. On an equispaced lattice, the resulting eigenvalue problem is identical to a finite-difference approximation of the Schrödinger equation. We find numerically that the antisymmetric sector has an energy spectrum that converges to the usual Coulomb spectrum as the lattice spacing is reduced. For the symmetric sector, in contrast, the effect of the lattice spacing is similar to that of a continuum self-adjointness boundary condition at $x=0$, and its effect on the ground state is significant even if the spacing is much below the Bohr radius. Boundary conditions at the singularity thus have a significant effect on the polymer quantization spectrum even after the singularity has been regularized.

We investigate the instability of the massive scalar field in the vicinity of a rotating black hole. The instability arises from amplification caused by the classical superradiance effect. The instability affects bound states: solutions to the massive Klein-Gordon equation which tend to zero at infinity. We calculate the spectrum of bound state frequencies on the Kerr background using a continued-fraction method, adapted from studies of quasinormal modes. We demonstrate that the instability is most significant for the $l=1$, $m=1$ state, for $M\mu \lesssim 0.5$. For a fast rotating hole ($a=0.99$) we find a maximum growth rate of ${\tau }^{-1}\approx 1.5\times {10}^{-7}(GM/c^3{)}^{-1}$, at $M\mu \approx 0.42$. The physical implications are discussed.

The mass matrices of the charged leptons and neutrinos, previously derived in a minimal $S_3$-invariant extension of the standard model, were reparametrized in terms of their eigenvalues. We obtained explicit, analytical expressions for all entries in the neutrino mixing matrix, $V_{\mathrm{PMNS}}$, the neutrino mixing angles, and the Majorana phases as functions of the masses of charged leptons and neutrinos in excellent agreement with the latest experimental values. The resulting $V_{\mathrm{PMNS}}$ matrix is very close to the tribimaximal form of the neutrino mixing matrix. We also derived explicit, analytical expressions for the matrices of the Yukawa couplings and computed the branching ratios of some selected flavor-changing neutral current processes as functions of the masses of the charged leptons and the neutral Higgs bosons. We find that the $S_3\times Z_2$ flavor symmetry and the strong mass hierarchy of the charged leptons strongly suppress the FCNC processes in the leptonic sector well below the present experimental upper bounds by many orders of magnitude.

The pseudoparticle approach is a numerical technique to compute path integrals without discretizing spacetime. The basic idea is to integrate over those field configurations, which can be represented by a sum of a fixed number of localized building blocks (pseudoparticles). In a couple of previous papers we have successfully applied the pseudoparticle approach to pure SU(2) Yang-Mills theory. In this work I discuss how to incorporate fermionic fields in the pseudoparticle approach. To test the method, I compute the phase diagram of the $1+1$-dimensional Gross-Neveu model in the large-$N$ limit.

If the two lightest neutralinos of the minimal supersymmetric standard model have a mass splitting less than the $Z$ boson mass, interference effects in the three-body decay ${\tilde{\chi }}_2^0\to {\tilde{\chi }}_1^{0}f\overline{f}$ can be important. We formulate an observable that contains information on the nature of the interference: the ratio $\mathrm{BR}({\tilde{\chi }}_2^0\to {\tilde{\chi }}_1^{0}b\overline{b})/\mathrm{BR}({\tilde{\chi }}_2^0\to {\tilde{\chi }}_1^0{l}^{+}{l}^{-})$. This will give a constraint on the supersymmetry breaking parameters that is complementary to many techniques already existing in the literature. We present some ideas on how to perform a simple counting experiment to determine this ratio.

Using recent CLEO III results for the cross section for $e^{+}{e}^{-}\to \mathrm{\text{hadrons}}$ at seven center-of-mass energies between 6.964 and 10.538 GeV, we derive a value for the strong coupling constant ${\alpha }_s(M_Z^2)={0.110}_{-0.012-0.011}^{-0.010+0.010}$ where the uncertainties are uncorrelated and correlated, respectively. Our result differs significantly from the one derived by CLEO III, as a consequence of inclusion of quark mass effects and the proper matching between the effective theories with four and five flavors. Combining this new result with an analysis based on earlier cross section measurements in the energy region between 2 and 10.6 GeV, we obtain ${\alpha }_s(M_Z^2)={0.119}_{-0.011}^{+0.009}$, well consistent with the current world average.

A scenario combining a model of early (TeV) unification of quarks and leptons with the physics of large extra dimensions provides a natural mechanism linking quark and lepton masses at TeV scale. This has been dubbed as early quark-lepton mass unification by one of us (P. Q. H.) in one of the two models of early quark-lepton unification, which are consistent with data, namely $\mathrm{SU}(4{)}_{\mathrm{PS}}\otimes \mathrm{SU}(2{)}_L\otimes \mathrm{SU}(2{)}_R\otimes \mathrm{SU}(2{)}_H$. In particular, it focused on the issue of naturally light Dirac neutrino. The present paper will focus on similar issues in the other model, namely $\mathrm{SU}(4{)}_{\mathrm{PS}}\otimes \mathrm{SU}(3{)}_L\otimes \mathrm{SU}(3{)}_H$.

In this paper we devise an alternative approach to the use of Padé approximants in the resummation of the perturbative (either divergent or convergent) series. Our procedure relies on the introduction of a nonphysical parameter and on the constraint that the physical observable be linear in this parameter. The relation between the unphysical parameter and the physical perturbative parameter is expressed in terms of a Padé approximant, whose form can be fully determined. We have applied this strategy to a number of examples and we have compared the results to those obtained following the standard Padé approach, observing that in many cases our approach is superior.

We study a Lagrangian formalism that avoids double counting in effective field theories where distinct fields are used to describe different infrared momentum regions for the same particle. The formalism leads to extra subtractions in certain diagrams and to a new way of thinking about factorization of modes in quantum field theory. In nonrelativistic field theories, the subtractions remove unphysical pinch singularities in box-type diagrams, and give a derivation of the known pullup mechanism between soft and ultrasoft fields which is required by the renormalization group evolution. In a field theory for energetic particles, the soft-collinear effective theory (SCET), the subtractions allow the theory to be defined with different infrared and ultraviolet regulators, remove double counting between soft, ultrasoft, and collinear modes, and give results which reproduce the infrared divergences of the full theory. Our analysis shows that convolution divergences in factorization formulas occur due to an overlap of momentum regions. We propose a method that avoids this double counting, which helps to resolve a long-standing puzzle with singularities in collinear factorization in QCD. The analysis gives evidence for a factorization in rapidity space in exclusive decays.

Combining the thermal operator representation with the dispersion relation in QED at finite temperature and chemical potential, we determine the complete retarded photon self-energy only from its absorptive part at zero temperature. As an application of this method, we show that, even for the case of a nonzero chemical potential, the temperature dependent part of the one loop retarded photon self-energy vanishes in $(1+1)$ dimensional massless QED.

We construct an exact classical solution of an Einstein-Yang-Mills system in ten space-time dimensions whose action contains a term quartic in Yang-Mills field strength. The solution provides compactification proposed by Cremmer and Scherk; the ten-dimensional space-time with a cosmological constant is compactified to the direct product of four-dimensional Minkowski space-time and a six-dimensional sphere $S^6$ whose radius is determined by coupling constants. We also construct a solution which compactifies the ten-dimensional space-time to ${\mathrm{AdS}}_4\times S^6$ when the cosmological constant is absent.

The hydrodynamics describing dynamical effects in superfluid neutron stars essentially differs from the standard one-fluid hydrodynamics. In particular, we have four bulk viscosity coefficients in the theory instead of one. In this paper we calculate these coefficients, for the first time, assuming they are due to nonequilibrium beta processes (such as modified or direct Urca process). The results of our analysis are used to estimate characteristic damping times of sound waves in superfluid neutron stars. It is demonstrated that all four bulk viscosity coefficients lead to comparable dissipation of sound waves and should be considered on the same footing.