The presence of light ($m_{\mathcal{A}}\sim {10}^{-6}\mathrm{eV}$) scalar fields in the early universe can modify the cosmology of neutrinos considerably by allowing their masses to vary on cosmological times. In this paper, we consider the effect of Planck-suppressed couplings of this scalar to electrons and show that such couplings easily can make new sterile states thermally inaccessible in the early universe, preserving the successes of big bang nucleosynthesis predictions. We consider the circumstances under which these effects give the proper initial conditions for recently considered models of neutrino dark energy, and consider limits from tests of the equivalence principle. The parameters which satisfy cosmological constraints naturally give rise to interesting signals in terrestrial neutrino oscillation experiments.

Superheavy particles are a natural candidate for the dark matter in the universe and our galaxy, because they are produced generically during inflation in cosmologically interesting amounts. The most attractive model for the origin of superheavy dark matter (SHDM) is gravitational production at the end of inflation. The observed cosmological density of dark matter determines the mass of the SHDM particle as $m_X=(\mathrm{\text{a few}})\times {10}^{13}\mathrm{GeV}$, promoting it to a natural candidate for the source of the observed ultrahigh energy cosmic rays (UHECR). After a review of the theoretical aspects of SHDM, we update its predictions for UHECR observations: no GZK cutoff, flat energy spectrum with $dN/dE\approx 1/E^{1.9}$, photon dominance and galactic anisotropy. We analyze the existing data and conclude that SDHM as explanation for the observed UHECRs is at present disfavored but not yet excluded. We calculate the anisotropy relevant for future Auger observations that should be the conclusive test for this model. Finally, we emphasize that negative results of searches for SHDM in UHECR do not disfavor SHDM as a dark matter candidate. Therefore, UHECRs produced by SHDM decays and with the signatures as described should be searched for in the future as subdominant effect.

Using configuration space techniques, we calculate next-to-leading order (NLO) five-loop QCD corrections to the correlators of interpolating pentaquark currents in the limit of massless quarks. We obtain very large NLO corrections to the spectral density which makes a standard sum rule analysis problematic. However, the NLO corrections to the correlator in configuration space are reasonable. We discuss the implications of our results for the phenomenological sum rule analysis of pentaquark states.

We study the implications of minimal flavor violating low energy supersymmetry scenarios for the search of new physics in the $B$ and Higgs sectors at the Tevatron collider and the LHC. We show that the already stringent Tevatron bound on the decay rate $B_s\to {\mu }^{+}{\mu }^{-}$ sets strong constraints on the possibility of generating large corrections to the mass difference $\Delta M_s$ of the $B_s$ eigenstates. We also show that the $B_s\to {\mu }^{+}{\mu }^{-}$ bound together with the constraint on the branching ratio of the rare decay $b\to s\gamma$ has strong implications for the search of light, nonstandard Higgs bosons at hadron colliders. In doing this, we demonstrate that the former expressions derived for the analysis of the double penguin contributions in the Kaon sector need to be corrected by additional terms for a realistic analysis of these effects. We also study a specific nonminimal flavor violating scenario, where there are flavor changing gluino-squark-quark interactions, governed by the Cabibbo-Kobayashi-Maskawa (CKM) matrix elements, and show that the $B$ and Higgs physics constraints are similar to the ones in the minimal flavor violating case. Finally we show that, in scenarios like electroweak baryogenesis which have light stops and charginos, there may be enhanced effects on the $B$ and $K$ mixing parameters, without any significant effect on the rate of $B_s\to {\mu }^{+}{\mu }^{-}$.

The transformation properties of strong penguin operators under the action of the flavor group change when they are considered as operators in (partially) quenched QCD instead of the unquenched theory. As a result, additional operators and new low-energy constants appear in the effective theory describing nonleptonic kaon decay matrix elements in the partially quenched setting. These new low-energy constants do not have a counterpart in the unquenched theory, and should thus be considered as an artifact of the quenched approximation. Here we consider strong penguin operators consisting of products of two left-handed flavor currents, and give a complete one-loop analysis in the effective theory for $K^0$ to vacuum and $K^{+}$ to ${\pi }^{+}$ matrix elements. We find that the new low-energy constants already appear in these matrix elements at leading order. This implies that (partially) quenched lattice computations of for instance the $\Delta I=1/2$ rule are affected by ambiguities intrinsic to the use of the quenched approximation at leading order. The only exception is the partially quenched case with three light sea quarks, consistent with general expectations. Our results are also relevant when the charm quark is kept in the theory.

Using the potentials derived from vector-meson-exchanges, the $K\overline{K}$, $DK$, $B\overline{K}$, $D\overline{D}$, $B\overline{B}$, $BD$, $\overline{D}K$, $BK$ and $B\overline{D}$ systems are studied. Possible $S$-wave bound-states of two pseudoscalar mesons are discussed. We find that systems of $DB$, $D\overline{D}$, $B\overline{B}$ and $DK$ with isospin 0 are likely to form $S$-wave bound states via strong interactions while the others are unlikely to be bound by the strong interaction sector alone. With the Coulomb potential, the $K^{+}{K}^{-}$ system can form an atomic bound state - the kaonium. The influence of the one-meson-exchange potential on the ground-state energy of the kaonium and its decay widths to $\pi \pi$ and $\pi \eta$ are evaluated.

Nonrelativistic quark models of charmonia are tested by comparison of theoretical charmonium decay constants, form factors, and $\gamma \gamma$ widths with experiment and lattice gauge computations. The importance of relativistic effects, a running coupling, and the correct implementation of bound state effects are demonstrated. We describe how an improved model and computational techniques resolve several outstanding issues in previous nonrelativistic quark models such as the use of “correction” factors in quark model form factors, artificial energy prescriptions in decay constant calculations, and ad hoc phase space modifications. We comment on the small experimental value of $f_{\psi (3S)}$ and the D-wave component of the $J/\psi$. Decay constants and $\gamma \gamma$ widths for bottomonium are also presented.

We have searched for a heavy resonance decaying into a $Z+\mathrm{\text{jet}}$ final state in $p\overline{p}$ collisions at a center of mass energy of $1.96\mathrm{TeV}$ at the Fermilab Tevatron collider using the D0 detector. No indication for such a resonance was found in a data sample corresponding to an integrated luminosity of $370{\mathrm{pb}}^{-1}$. We set upper limits on the cross section times branching fraction for heavy resonance production at the 95% C.L. as a function of the resonance mass and width. The limits are interpreted within the framework of a specific model of excited quark production.

We derive an upper limit on the neutrino mass from the Wilkinson Microwave Anisotropy Probe (WMAP) three-year data alone by employing a deterministic minimization method based on a grid search in multiparameter space. Assuming the flat $\Lambda \mathrm{CDM}$ model with power-law adiabatic perturbations, we find $\sum _{}^{}{m}_{\nu }<2.0\mathrm{eV}$ in agreement with the result of the WMAP team. This result, the limit being nearly the same as that from the WMAP first-year data, means that the fundamental limit on the neutrino mass obtainable from the cosmic microwave background alone is already nearly met, as anticipated from the previous analysis. We also clarify the role of the polarization data in deriving the limit on the neutrino mass.

We derive the most general flux-induced superpotential for $\mathcal{N}=1$ $M$-theory compactifications on seven-dimensional manifolds with $SU(3)$ structure. Imposing the appropriate boundary conditions, this result applies for heterotic $M$-theory. It is crucial for the latter to consider $SU(3)$ and not $G_2$ group structure on the seven-dimensional internal space. For a particular background that differs from $\mathrm{CY}(3)\times S^1/{\mathbb{Z}}_2$ only by warp factors, we investigate the flux-generated scalar potential as a function of the orbifold length. We find a positive cosmological constant minimum, however at an undesirably large value of this length. Hence the flux superpotential alone is not enough to stabilize the orbifold length at a de Sitter vacuum. But it does modify substantially the interplay between the previously studied nonperturbative effects, possibly reducing the significance of open membrane instantons while underlining the importance of gaugino condensation.

The effect of quantum fluctuations on Bogomol’nyi-Prasad-Sommerfield (BPS)-saturated topological excitations in supersymmetric theories is studied. Focus is placed on a sequence of topological excitations that derive from the same classical soliton or vortex in lower dimensions and it is shown that their quantum characteristics, such as the spectrum and profile, differ critically with the dimension of spacetime. In all the examples examined the supercharge algebra retains its classical form although short-wavelength fluctuations may modify the operator structure of the central charge, yielding an anomaly. The central charge, when the expectation value is taken, is further affected by long-wavelength fluctuations, and this makes the BPS-excitation spectra only approximately calculable in some low-dimensional theories. In four dimensions, in contrast, holomorphy plays a special role in stabilizing the BPS-excitation spectra against quantum corrections. The basic tool in our study is the superfield supercurrent, from which the supercharge algebra with a central extension is extracted in a supersymmetric setting. A general method is developed to determine the associated superconformal anomaly by considering dilatation directly in superspace.

A classical analysis suggests that an external magnetic field can cause trajectories of charge carriers on a superconducting domain wall or cosmic string to bend, thus expelling charge carriers with energy above the mass threshold into the bulk. We study this process by solving the Dirac equation for a fermion of mass $m_f$ and charge $e$, in the background of a domain wall and a magnetic field of strength $B$. We find that the modes of the charge carriers get shifted into the bulk, in agreement with classical expectations. However the dispersion relation for the zero modes changes dramatically—instead of the usual linear dispersion relation, ${\omega }_k=k$, the new dispersion relation is well fit by $\omega \approx m_f\tanh (k/k_{*})$ where $k_{*}=m_f$ for a thin wall in the weak field limit, and $k_{*}=eBw$ for a thick wall of width $w$. This result shows that the energy of the charge carriers on the domain wall remains below the threshold for expulsion even in the presence of an external magnetic field. If charge carriers are expelled due to an additional perturbation, they are most likely to be ejected at the threshold energy $\sim m_f$.

A three-dimensional effective theory for high temperature $SU(3)$ gauge theory, which maintains the $Z(3)$ center symmetry of the full theory, is constructed. Such a $Z(3)$ invariant effective theory should be applicable to a wider temperature range than the usual effective theory, known as EQCD, which fails to respect the center symmetry. This center-symmetric effective theory can reproduce domain wall and phase transition properties that are not accessible in EQCD. After identifying a convenient class of $Z(3)$ invariant effective theories, we constrain the coefficients of the various terms in the Lagrangian using leading-order matching to EQCD at high temperature, plus matching of domain wall properties in the full theory. We sketch the expected structure of the phase diagram of the effective theory and briefly discuss the prospects of numerical simulations and the addition of quarks.

We prove that when the equations are restricted to the principal part the standard version of the Baumgarte-Shapiro-Shibata-Nakamura (BSSN) formulation of the Einstein equations is equivalent to the Nagy-Ortiz-Reula (NOR) formulation for any gauge, and that the Kidder-Scheel-Teukolsky (KST) formulation is equivalent to NOR for a variety of gauges. We review a family of elliptic gauge conditions and the implicit parabolic and hyperbolic drivers that can be derived from them, and show how to make them symmetry-seeking. We investigate the hyperbolicity of Arnowitt-Deser-Misner (ADM), NOR, and BSSN with implicit hyperbolic lapse and shift drivers. We show that BSSN with the coordinate drivers used in recent “moving puncture” binary black hole evolutions is ill-posed at large shifts, and suggest how to make it strongly hyperbolic for arbitrary shifts. For ADM, NOR, and BSSN with elliptic and parabolic gauge conditions, which cannot be hyperbolic, we investigate a necessary condition for well-posedness of the initial-value problem.

The holographic description in the presence of the gravitational Chern-Simons term is studied. The modified gravitational equations are integrated by using the Fefferman-Graham expansion, and the holographic stress-energy tensor is identified. The stress-energy tensor has both conformal anomaly and gravitational or, if reformulated in terms of the zweibein, Lorentz anomaly. We comment on the structure of anomalies in two dimensions and show that the two-dimensional stress-energy tensor can be reproduced by integrating the conformal and gravitational anomalies. We study the black hole entropy in theories with a gravitational Chern-Simons term and find that the usual Bekenstein-Hawking entropy is modified. For the Banados-Teitelboim-Zanelli (BTZ) black hole, the modification is determined by the area of the inner horizon. We show that the total entropy of the BTZ black hole is precisely reproduced in a boundary conformal field theory calculation using the Cardy formula.

We study constraints on time variation of the fine structure constant $\alpha$ from cosmic microwave background (CMB) taking into account simultaneous change in $\alpha$ and the electron mass $m_e$ which might be implied in unification theories. We obtain the constraints $-0.097<\Delta \alpha /\alpha <0.034$ at 95% C.L. using WMAP data only, and $-0.042<\Delta \alpha /\alpha <0.026$ combining with the constraint on the Hubble parameter by the HST Hubble Key Project. These are improved by 15% compared with constraints assuming only $\alpha$ varies. We discuss other relations between variations in $\alpha$ and $m_e$ but we do not find evidence for varying $\alpha$.

We reanalyze the implications of the DAMA/NaI experiment for mirror matter-type dark matter, taking into account information from the energy dependence of the DAMA annual modulation signal. This is combined with the null results from the CDMS experiment, leading to fairly well defined allowed regions of parameter space. The allowed regions of parameter space will be probed in the near future by the DAMA/LIBRA, CDMS, and other experiments, which should either exclude or confirm this explanation of the DAMA/NaI annual modulation signal. In particular, we predict that the CDMS experiments should find a positive signal around the threshold recoil energy region, $E_R<15\mathrm{keV}$ in the near future.

We extend the formalism of Leibovich, Ligeti, Stewart and Wise in the $1/m_Q$ expansion of Heavy Quark Effective Theory for the $\overline{B}$ semileptonic decays into excited $D(\frac{3}{2}{}^{+})$ mesons to the opposite parity states $D(\frac{3}{2}{}^{-})$. For $D(\frac{3}{2}{}^{+})$ the $1/m_Q$ current perturbation dominates over the leading term at zero recoil, while for $D(\frac{3}{2}{}^{-})$ the $1/m_Q$ perturbation due to ${\mathcal{L}}_{\mathrm{mag}}$ dominates also at zero recoil. We show that the corresponding $1/m_Q$ magnetic coupling is proportional to the mixing between the states $D(\frac{3}{2}{}^{-},1^{-})$ and $D(\frac{1}{2}{}^{-},1^{-})$ induced by the tensor force. We point out some subtleties that appear in this respect in HQET.

We investigate the possibility of generating the $\mu$-term in the minimal supersymmetric standard model (MSSM) by the condensation of a field that is a singlet under the standard model (SM) gauge group but charged under an additional family-independent $U(1{)}_X$ gauge symmetry. We attempt to do so while preserving the gauge coupling unification of the MSSM. For this, we find that SM nonsinglet exotics must be present in the spectrum. We also prove that the pure $U(1{)}_X$ anomalies can always be solved with rationally charged fields, but that a large number of SM singlets are often required. For $U(1{)}_X$ charges that are consistent with an embedding of the MSSM in $SU(5)$ or $SO(10)$, we show that the $U(1{)}_X$ charges of the MSSM states can always be expressed as a linear combination of Abelian subgroups of $E_6$. However, the SM exotics do not appear to have a straightforward embedding into grand-unified theory multiplets. We conclude from this study that if this approach to the $\mu$-term is correct, as experiment can probe, it will necessarily complicate the standard picture of supersymmetric grand unification.