Quantum gravity is made more difficult in part by its constraint structure. The constraints are classically first-class; however, upon quantization they become partially second-class. To study such behavior, we focus on a simple problem with finitely many degrees of freedom and demonstrate how the projection operator formalism for dealing with quantum constraints is well suited to this type of example.

We consider our universe as a 3d domain wall embedded in a 5d dimensional Minkowski space-time. We address the problem of inflation and late time acceleration driven by bulk particles colliding with the 3d domain wall. The expansion of our universe is mainly related to these bulk particles. Since our universe tends to be permeated by a large number of isolated structures, as temperature diminishes with the expansion, we model our universe with a 3d domain wall with increasing internal structures. These structures could be unstable 2d domain walls evolving to fermi-balls which are candidates to cold dark matter. The momentum transfer of bulk particles colliding with the 3d domain wall is related to the reflection coefficient. We show a nontrivial dependence of the reflection coefficient with the number of internal dark matter structures inside the 3d domain wall. As the population of such structures increases the velocity of the domain wall expansion also increases. The expansion is exponential at early times and polynomial at late times. We connect this picture with string/M-theory by considering BPS 3d domain walls with structures which can appear through the bosonic sector of a five-dimensional supergravity theory.

We study a simple model of a massive inflaton field $\varphi$ coupled to another scalar filed $\chi$ with interaction term $g^2{\varphi }^2{\chi }^2$. We use the theory developed by Kofman et al. [L. Kofman, A. D. Linde, and A. A. Starobinsky, Phys. Rev. D 56, 3258 (1997).] for the first stage of preheating to give a full description of the dynamics of the $\chi$ field modes, including the behavior of the phase, in terms of the iteration of a simple family of circle maps. The parameters of this family of maps are a function of time when expansion of the Universe is taken into account. With this more detailed description, we obtain a systematic study of the efficiency of particle production as a function of the inflaton field and coupling parameters, and we find that for $g\lesssim 3\times {10}^{-4}$ the broad resonance ceases during the first stage of preheating.

We consider a natural generalization of trinification to theories with $3N$ SU(3) gauge groups. These theories have a simple moose representation and a gauge boson spectrum that can be interpreted via the deconstruction of a 5D theory with unified symmetry broken on a boundary. Although the matter and Higgs sectors of the theory have no simple extra-dimensional analog, gauge unification retains features characteristic of the 5D theory. We determine possible assignments of the matter and Higgs fields to unified multiplets and present theories that are viable alternatives to minimal trinified GUTs.

The common belief that the lightest supersymmetric particle might be a neutralino, providing also the main dark matter component, calls for maximal detail in the study of the neutralino properties. Motivated by this, we consider the direct production of a single neutralino ${\tilde{\chi }}_i^0$ at a high/energy hadron collider, focusing on the ${\tilde{\chi }}_1^0$ and ${\tilde{\chi }}_2^0$ cases. At Born level, the relevant subprocesses are $q\overline{q}\to {\tilde{\chi }}_i^0\tilde{g}$, $gq\to {\tilde{\chi }}_i^0{\tilde{q}}_{L,R}$, and $q{\overline{q}}^{\prime }\to {\tilde{\chi }}_i^0{\tilde{\chi }}_j^{\pm }$; while at one-loop, apart from radiative corrections to these processes, we consider also $gg\to {\tilde{\chi }}_i^0\tilde{g}$, for which a numerical code named PLATONgluino is released. The relative importance of these channels turns out to be extremely model dependent. Combining these results with an analogous study of the direct ${\tilde{\chi }}_i^0{\tilde{\chi }}_j^0$ pair production should help in testing the supersymmetric models and the dark matter assignment.

To realize the condition of ${sin}^{2}2{\vartheta }_{12}\gg {sin}^2{\vartheta }_{13}$, we find constraints on flavor neutrino masses $M_{ij}$ ($ij=e,\mu ,\tau$): (C1) $c_{23}^2{M}_{\mu \mu }+s_{23}^2{M}_{\tau \tau }\approx 2s_{23}{c}_{23}{M}_{\mu \tau }+M_{ee}$ and/or (C2) $|c_{23}{M}_{e\mu }-s_{23}{M}_{e\tau }|\gg |s_{23}{M}_{e\mu }+c_{23}{M}_{e\tau }|$, where $c_{23}=\cos {\vartheta }_{23}$ ($s_{23}=\sin {\vartheta }_{23}$) and ${\vartheta }_{12}$, ${\vartheta }_{13}$, and ${\vartheta }_{23}$ are the mixing angles for three flavor neutrinos. The applicability of (C1) and (C2) is examined in models with one massless neutrino and two massive neutrinos suggested by $\det (M)=0$, where $M$ is a mass matrix constructed from $M_{ij}$ ($i,j=e,\mu ,\tau$). To make definite predictions on neutrino masses and mixings, especially on $\sin {\vartheta }_{13}$, that enable us to trace (C1) and (C2), $M$ is assumed to possess texture zeros or to be constrained by textures with $M_{\mu \mu }=M_{\tau \tau }$ or $M_{e\tau }=\pm M_{e\mu }$, which turn out to ensure the emergence of the maximal atmospheric neutrino mixing at $\sin {\vartheta }_{13}\to 0$. It is found that (C1) is used by textures such as $M_{e\mu }=0$ or $M_{e\tau }=0$, while (C2) is used by textures such as $M_{e\tau }=\pm M_{e\mu }$.

We compute the leading, chiral charge-changing relaxation term in the quantum transport equations that govern electroweak baryogenesis using the closed time path formulation of nonequilibrium quantum field theory. We show that the relaxation transport coefficients may be resonantly enhanced under appropriate conditions on electroweak model parameters and that such enhancements can mitigate the impact of similar enhancements in the $CP$-violating source terms. We also develop a power counting in the time and energy scales entering electroweak baryogenesis and include effects through second order in ratios $ϵ$ of the small and large scales. We illustrate the implications of the resonantly enhanced $\mathcal{O}({ϵ}^2)$ terms using the Minimal Supersymmetric Standard Model, focusing on the interplay between the requirements of baryogenesis and constraints obtained from collider studies, precision electroweak data, and electric dipole moment searches.

We study the decay of ${\Theta }^{+}$ in a nonrelativistic quark model. The wave function of ${\Theta }^{+}$ is constructed for the two cases $J^P=1/2^{\pm }$ as products of color, spin, flavor, and orbital parts respecting total antisymmetrization among the four quarks. We find that for the negative parity ${\Theta }^{+}$ the width becomes very large which is of order of several hundreds MeV, while it is about a several tens MeV for the positive parity. By assuming additionally diquark correlations, the width is reduced to be of order 10 MeV. It is also pointed out that a similar calculation for $3/2^{-}$ results in strong suppression of its width.

We present a detailed calculation of the electron-positron production rate using neutrinos in an intense laser field. The computation is done for the process $\nu \to \nu e\overline{e}$ via the neutral channel and within the framework of the standard model. The production rates are tabulated for a broad range of incoming neutrino energies and in an electromagnetic field similar to what can be attained by current high-intensity lasers.

We present a set of scalar master integrals (MIs) needed for a complete treatment of massive two-loop corrections to Bhabha scattering in QED, including integrals with arbitrary fermionic loops. The status of analytical solutions for the MIs is reviewed and examples of some methods to solve MIs analytically are worked out in more detail. Analytical results for the pole terms in $ϵ$ of so far unknown box MIs with five internal lines are given.

We present a new, completely revised calculation of the muon anomalous magnetic moment $a_{\mu }=(g_{\mu }-2)/2$ comparing it with the more recent experimental determination of this quantity; this furnishes an important test of theories of strong, weak, and electromagnetic interactions. These theoretical determinations give the very precise numbers, ${10}^{11}\times a_{\mu }=116591806\pm 50\pm 10(\mathrm{rad})\pm 30(\ell \times \ell )[\mathrm{Theory},\mathrm{no}\tau ]$ and ${10}^{11}\times a_{\mu }=116591889\pm 49\pm 10(\mathrm{rad})\pm 30(\ell \times \ell )[\mathrm{Theory},\tau ]$ to be compared with the experimental number, ${10}^{11}\times a_{\mu }=116592080\pm 60$. In the theoretical evaluations, the first quantity does not, and the second one does, use information from $\tau$ decay. The first errors for the theoretical evaluations include statistical plus systematic errors; the other ones are the estimated errors due to incomplete treatment of radiative corrections and the estimated error in the light-by-light scattering contribution. We thus have a significant mismatch between theory and experiment. We also use part of the theoretical calculations to give a precise evaluation of the electromagnetic coupling on the $Z$, ${\overline{\alpha }}_{\mathrm{QED}}(M_Z^2)$, of the masses and widths of the (charged and neutral) rho resonances, of the scattering length and effective range for the $P$ wave in $\pi \pi$ scattering, and of the quadratic radius and second coefficient of the pion form factor.

We study the decay $B^{-}\to J/\psi K^{-}{\pi }^{+}{\pi }^{-}$ using $117\times {10}^6$ $B\overline{B}$ events collected at the $Y(4S)$ resonance with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ asymmetric-energy storage ring. We measure the branching fractions $\mathcal{B}$ $(B^{-}\to J/\psi K^{-}{\pi }^{+}{\pi }^{-})=(116\pm 7(\mathrm{stat}.)\pm 9(\mathrm{syst}.))\times {10}^{-5}$ and $\mathcal{B}$ $(B^{-}\to X(3872){\mathrm{K}}^{-})\times$ $\mathcal{B}$ $(X(3872)\to \mathrm{J}/\psi {\pi }^{+}{\pi }^{-})=(1.28\pm 0.41)\times {10}^{-5}$ and find the mass of the $X(3872)$ to be $3873.4\pm 1.4\mathrm{MeV}/{\mathrm{c}}^2$. We search for the $h_c$ narrow state in the decay $B^{-}\to h_c{K}^{-}$, $h_c\to J/\psi {\pi }^{+}{\pi }^{-}$ and for the decay $B^{-}\to J/\psi D^0{\pi }^{-}$, with $D^0\to K^{-}{\pi }^{+}$. We set the $90\%$ C.L. limits $\mathcal{B}(B^{-}\to h_c{K}^{-})\times \mathcal{B}(h_c\to J/\psi {\pi }^{+}{\pi }^{-})<3.4\times {10}^{-6}$ and $\mathcal{B}(B^{-}\to J/\psi D^0{\pi }^{-})<5.2\times {10}^{-5}$.

In this paper we study the sensitivity of the flux of atmospheric muons to uncertainties in the primary cosmic ray spectrum and to the treatment of the geomagnetic field. We use the air shower simulation program AIRES to make the calculation for two different primary spectra and under several approximations to the propagation of charged particles in the geomagnetic field. The results illustrate the importance of accurate modeling of the geomagnetic field effects. We propose a high and a low fit of the proton and helium fluxes, and calculate the muon fluxes with these different inputs. Comparison with measurements of the muon flux by the CAPRICE experiment shows a slight preference for the higher primary cosmic ray flux parametrization.

We obtain the bounds on arbitrary linear combinations of operators of dimension 6 in the Standard Model. We consider a set of 21 flavor and $CP$ conserving operators. Each of our 21 operators is tightly constrained by the standard set of electroweak measurements. We perform a fit to all relevant precision electroweak data and include neutrino scattering experiments, atomic parity violation, W mass, LEP1, SLD, and LEP2 data. Our results provide an efficient way of obtaining bounds on weakly coupled extensions of the standard model.

We analyze the QCD dynamics of diffractive deep inelastic scattering. The presence of a rapidity gap between the target and diffractive system requires that the target remnant emerges in a color-singlet state, which we show is made possible by the soft rescattering of the struck quark. This rescattering is described by the path-ordered exponential (Wilson line) in the expression for the parton distribution function of the target. The multiple scattering of the struck parton via instantaneous interactions in the target generates dominantly imaginary diffractive amplitudes, giving rise to an “effective Pomeron” exchange. The Pomeron is not an intrinsic part of the proton but a dynamical effect of the interaction. This picture also applies to diffraction in hadron-initiated processes. Because of the different color environment the rescattering is different in virtual photon- and hadron-induced processes, explaining the observed nonuniversality of diffractive parton distributions. This framework provides a theoretical basis for the phenomenologically successful soft color interaction (SCI) model which includes rescattering effects and thus generates a variety of final states with rapidity gaps. We discuss developments of the SCI model to account for the color coherence features of the underlying subprocesses.

We consider the effective two-Higgs-doublet potential with complex parameters, when the $CP$ invariance is broken both explicitly and spontaneously. The diagonal mass term in the local minimum of the potential is constructed for the physical basis of Higgs fields, keeping explicitly the limiting case of $CP$ conservation, if the parameters are taken real. For the special case of the two-doublet Higgs sector of the minimal supersymmetric model, when $CP$ invariance is violated by the Higgs bosons interaction with scalar quarks of the third generation, we calculate by means of the effective potential method the Higgs boson masses and evaluate the two-fermion Higgs boson decay widths and the widths of rare one-loop-mediated decays $H\to \gamma \gamma$, $H\to gg$.

The $b\to s$ penguin amplitude affects a number of $B$ meson decays to two pseudoscalar ($P$) mesons in which potential anomalies are being watched carefully, though none has yet reached a statistically compelling level. These include (a) a sum of rates for $B^0\to K^0{\pi }^0$ and $B^{+}\to K^{+}{\pi }^0$ enhanced relative to half the sum for $B^0\to K^{+}{\pi }^{-}$ and $B^{+}\to K^0{\pi }^{+}$, (b) a time-dependent $CP$ asymmetry parameter $S$ for $B^0\to K^0{\pi }^0$ which is low in comparison with the expected value of $\sin 2\beta \simeq 0.73$, and (c) a similar deviation in the parameter $S$ for $B^0\to {\eta }^{\prime }{K}_S$. These and related phenomena involving vector mesons in the final state are discussed in a unified way in and beyond the standard model. Future experiments which would conclusively indicate the presence of new physics are identified. Several of these involve decays of the strange $B$ meson $B_s$. In the standard model we prove an approximate sum rule for $CP$ rate differences in $B^0\to K^{+}{\pi }^{-}$, $B^{+}\to K^{+}{\pi }^0$ and $B^0\to K^0{\pi }^0$, predicting a negative sign for the latter asymmetry.

We construct a one-parameter family of flat currents in $Ad{S}_5\times S^1$ and $Ad{S}_3\times S^3$ Green-Schwarz superstrings, which would naturally lead to a hierarchy of classical conserved nonlocal charges. In the former case we rewrite the $Ad{S}_5\times S^1$ string using a new ${\mathbb{Z}}_4$-graded base of the superalgebra $su(2,2|2)$. In both cases the existence of the ${\mathbb{Z}}_4$ grading in the superalgebras plays a key role in the construction. As a result, we find that the flat currents, when formally written in terms of the ${\mathcal{G}}_0$-gauge invariant lowercase 1-forms, take the same form as the one in the $Ad{S}_5\times S^5$ case.

By shining a hypermultiplet from one side of the bulk of a flat five-dimensional orbifold, supersymmetry can be broken by boundary conditions. The extra dimension is stabilized in a supersymmetric way, and by computing the four-dimensional effective potential for the radion it is shown that supersymmetry breaking does not damage our radius stabilization mechanism. The low energy theory contains the radion and two complex scalars that are massless in the global supersymmetric limit and are stabilized by tree-level supergravity effects. It is shown that radion mediation can play the dominant role in communicating supersymmetry breaking to the visible sector. It is also shown that at tree level, contact terms are exponentially suppressed.