The Wheeler-DeWitt equation arising from a Kantowski-Sachs model is considered for a Schwarzschild black hole under the assumption that the scale factors and the associated momenta satisfy a noncanonical noncommutative extension of the Heisenberg-Weyl algebra. An integral of motion is used to factorize the wave function into an oscillatory part and a function of a configuration space variable. The latter is shown to be normalizable using asymptotic arguments. It is then shown that on the hypersurfaces of constant value of the argument of the wave function’s oscillatory piece, the probability vanishes in the vicinity of the black hole singularity.

Models with a nonuniversal $Z^{\prime }$ exhibit in general flavor changing neutral currents at tree-level. When the $Z^{\prime }$ couplings favor the third generation, flavor changing transitions of the form $Z^{\prime }tc$ and $Z^{\prime }tu$ could be large enough to be observable at the LHC. In this paper we explore this possibility using the associated production of a single top-quark with the $Z^{\prime }$ and find that integrated luminosities of a few hundred ${\mathrm{fb}}^{-1}$ are necessary to probe the interesting region of parameter space.

We extend our earlier lattice-QCD analysis of heavy-quark correlators to smaller lattice spacings and larger masses to obtain new values for the $c$ mass and QCD coupling, and, for the first time, values for the $b$ mass: $m_c(3\mathrm{GeV},n_f=4)=0.986(6)\mathrm{GeV}$, ${\alpha }_{\overline{\mathrm{MS}}}(M_Z,n_f=5)=0.1183(7)$, and $m_b(10\mathrm{GeV},n_f=5)=3.617(25)\mathrm{GeV}$. These are among the most accurate determinations by any method. We check our results using a nonperturbative determination of the mass ratio $m_b(\mu ,n_f)/m_c(\mu ,n_f)$; the two methods agree to within our 1% errors and taken together imply $m_b/m_c=4.51(4)$. We also update our previous analysis of ${\alpha }_{\overline{\mathrm{MS}}}$ from Wilson loops to account for revised values for $r_1$ and $r_1/a$, finding a new value ${\alpha }_{\overline{\mathrm{MS}}}(M_Z,n_f=5)=0.1184(6)$; and we update our recent values for light-quark masses from the ratio $m_c/m_s$. Finally, in the Appendix, we derive a procedure for simplifying and accelerating complicated least-squares fits.

Motivated by the recent unexpected large forward-backward asymmetry of the top-quark observed by D0 and CDF at the Tevatron, we investigate a possible explanation for the anomaly within the framework of diquark models. In the diquark models, the top-quark pair production is mediated by the $u$-channel diagram. It is found that the color-triplet diquark can generate the forward-backward asymmetry of 20% when the constraint from the cross section of the top-quark pair production is taken into account.

We investigate the impact of charm mixing on a model-independent $\gamma$ measurement using the Dalitz plot analysis of the three-body $D$ decay from the $B^{+}\to D{K}^{+}$ process, and show that ignoring the mixing at all stages of the analysis is safe up to a sub-degree level of precision. We also find that in the coherent production of the $D^0{\overline{D}}^{*0}$ system in $e^{+}{e}^{-}$ collisions, the effect of charm mixing is enhanced, and propose a model-independent method to measure charm mixing parameters in time-integrated Dalitz plot analysis at charm factories.

We present a study of the Higgs boson decay branching ratios to $b\overline{b}$, $c\overline{c}$, and gluons, one of the cornerstones of the physics program at the International Linear Collider. A standard model Higgs boson of 120 GeV mass, produced in the Higgs-strahlung process at $\sqrt{s}=250\mathrm{GeV}$, was investigated using the full detector simulation and reconstruction procedures. The analysis was performed in the framework of the Silicon Detector concept with full account of inclusive standard model backgrounds. The selected decay modes contained two heavy flavor jets in the final state and required excellent flavor tagging through precise reconstruction of interaction and decay vertices in the detector. A new signal discrimination technique using correlations of neural network outputs was used to determine the branching ratios and estimate their uncertainties, 4.8%, 8.4%, and 12.2% for $b\overline{b}$, $c\overline{c}$, and gluons, respectively.

Primordial black hole (PBH) abundance limits constrain the primordial power spectrum, and hence models of inflation, on scales far smaller than those probed by cosmological observations. Single field inflation models compatible with all cosmological data can have large enough perturbations on small scales to overproduce PBHs, and hence be excluded. The standard formulas for the amplitude of perturbations do not hold for modes that exit the horizon close to the end of inflation however. We use a modified flow analysis to identify models where the amplitude of perturbations on small scales is large. For these models we carry out a numerical evolution of the perturbations and use PBH constraints to eliminate models which overproduce PBHs. We demonstrate that PBHs strongly constrain models of inflation and show that a numerical evaluation of the power spectrum decreases the number of otherwise viable models.

The CMB constrains the cosmological-birefringence rotation angle to be $|\alpha |\lesssim 1°$ ($1\sigma$) out to redshifts $z\simeq 1100$ for a rotation that is uniform across the sky. However, the rotation angle $\alpha (\theta ,\varphi )$ may vary with position $(\theta ,\varphi )$ on the sky, and if so, then it can be sought in current and future active galactic nuclei data. An upper limit $⟨{\alpha }^2{⟩}^{1/2}\lesssim 3.7°$ to the scatter in the position-angle–polarization offsets in a sample of only $N=9$ active galactic nuclei already constrains the rotation spherical-harmonic coefficients to $(4\pi {)}^{-1/2}{\alpha }_{lm}\lesssim 3.7°$ and constrains the power spectrum for $\alpha$ in models where it is a stochastic field. Future constraints can be improved with more sources and by analyzing well-mapped sources with a tensor-harmonic decomposition of the polarization.

It can be shown in a solvable field theory model that the couplings of the composite vector bosons made of a fermion pair approach the gauge couplings in the limit of strong binding. Although this phenomenon may appear accidental and special to the vector bosons made of a fermion pair, we extend it to the case of bosons being constituents and find that the same phenomenon occurs in a more intriguing way. The functional formalism not only facilitates computation but also provides us with a better insight into the generating mechanism of approximate gauge symmetry, in particular, how the strong binding and global current conservation conspire to generate such an approximate symmetry. Remarks are made on its possible relevance or irrelevance to electroweak and higher symmetries.

Spherically symmetric gravitationally bound, oscillating scalar lumps (boson stars and oscillatons) are considered in Einstein’s gravity coupled to massive scalar fields in $1+D$-dimensional de Sitter-type inflationary space-times. We show that due to inflation bosons stars and oscillatons lose mass through scalar radiation, but at a rate that is exponentially small when the expansion rate is slow.

Fluctuations around a Bose-Einstein condensate can be described by means of Bogolubov theory leading to the notion of quasiparticle and antiquasiparticle familiar to nonrelativistic condensed-matter practitioners. On the other hand, we already know that these perturbations evolve according to a relativistic Klein-Gordon equation in the long-wavelength approximation. For shorter wavelengths, we show that this equation acquires nontrivial corrections which modify the Klein-Gordon product. In this approach, quasiparticles can also be defined (up to the standard ambiguities due to observer dependence). We demonstrate that—in the low-energy as well as in the high-energy regimes—both concepts of quasiparticle are actually the same, regardless of the formalism (Bogolubov or Klein-Gordon) used to describe them. These results also apply to any barotropic, inviscid, irrotational fluid, with or without quantum potential. Finally, we illustrate how the quantization of these systems of quasiparticles proceeds by analyzing a stationary configuration containing an acoustic horizon. We show that there are several possible choices of a regular vacuum state, including a regular generalization of the Boulware vacuum. Issues such us Hawking radiation crucially depend on this vacuum choice.

We present and analyze new exact gyraton solutions of algebraic type II on a background which is a static, cylindrically symmetric Melvin universe of type D. For a vanishing electromagnetic field it reduces to previously studied gyratons on Minkowski background. We demonstrate that the solutions are a member of a more general family of the Kundt spacetimes. We show that the Einstein equations reduce to a set of mostly linear equations on a transverse 2-space and we discuss the properties of polynomial scalar curvature invariants which are generally nonconstant but unaffected by the presence of gyratons.

We study string gas dynamics in the early universe and seek to realize the Brandenberger-Vafa mechanism—a goal that has eluded earlier works—that singles out three or fewer spatial dimensions as the number that grows large cosmologically. Considering wound string interactions in an impact parameter picture, we show that a strong exponential suppression in the interaction rates for $d>3$ spatial dimensions reflects the classical argument that string world sheets generically intersect in at most four spacetime dimensions. This description is appropriate in the early universe if wound strings are heavy—wrapping long cycles—and diluted. We consider the dynamics of a string gas coupled to dilaton gravity and find that (a) for any number of dimensions the universe generically stays trapped in the Hagedorn regime and (b) if the universe fluctuates to a radiation regime any residual winding modes are diluted enough so that they freeze-out in $d>3$ large dimensions while they generically annihilate for $d=3$. In this sense the Brandenberger-Vafa mechanism is operative.

Measurements of the baryonic acoustic oscillation (BAO) peak in the redshift-space correlation function yield the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$ as a function of redshift, constraining the properties of dark energy and space curvature. We discuss the perturbations introduced in the galaxy correlation function by gravitational lensing through the effect of magnification bias and its cross correlation with the galaxy density. At the BAO scale, gravitational lensing adds a small and slowly varying component to the galaxy correlation function and does not change its shape significantly, through which the BAO peak is measured. The relative shift in the position of the BAO peak caused by gravitational lensing in the angle-averaged correlation function is ${10}^{-4}$ at $z=1$, rising to ${10}^{-3}$ at $z=2.5$. Lensing effects are stronger near the line of sight; however, the relative peak shift increases only to ${10}^{-3.3}$ and ${10}^{-2.4}$ at $z=1$ and $z=2.5$, when the galaxy correlation is averaged within 5 degrees of the line of sight (containing only 0.4% of the galaxy pairs in a survey). Furthermore, the lensing contribution can be measured separately and subtracted from the observed correlation at the BAO scale.

Motivated by the success of $A_4$ in explaining neutrino tribimaximal mixing, and its approximate residual $Z_3$ symmetry in the quark and charged-lepton sectors, the notion of flavor triality is proposed. Under this hypothesis, certain processes such as ${\tau }^{+}\to {\mu }^{+}{\mu }^{+}{e}^{-}$ and ${\tau }^{+}\to e^{+}{e}^{+}{\mu }^{-}$ are favored, but ${\tau }^{+}\to {\mu }^{+}{e}^{+}{e}^{-}$ and ${\mu }^{+}\to e^{+}{e}^{+}{e}^{-}$ are disfavored. Similarly, $B^0\to {\tau }^{+}{e}^{-}$ is favored, but $B^0\to {\tau }^{-}{e}^{+}$ is disfavored.

We consider a scalar dark-matter (DM) model, the $\mathrm{SM}4+\mathrm{D}$, consisting of the standard model with four generations (SM4) and a real gauge-singlet scalar called darkon, $D$, as the WIMP DM candidate. We explore constraints on the darkon sector of the $\mathrm{SM}4+\mathrm{D}$ from WIMP DM direct-search experiments, including CDMS-II and CoGeNT, and from the decay of a $B$ meson into a kaon plus missing energy. We find that a sizable portion of the darkon parameter space is still compatible with the experimental data. Since the darkon-Higgs interaction may give rise to considerable enhancement of the Higgs invisible decay mode, the existence of the darkon could lead to the weakening or evasion of some of the restrictions on the Higgs mass in the presence of fourth-generation quarks. In addition, it can affect the flavor-changing decays of these new heavy quarks into a lighter quark and the Higgs boson, as the Higgs may subsequently decay invisibly. Therefore, we also study these flavor-changing neutral transitions involving the darkon, as well as the corresponding top-quark decay $t\to cDD$, some of which may be observable at the Tevatron or LHC and thus provide additional tests for the $\mathrm{SM}4+\mathrm{D}$.

Exact chiral symmetry at finite lattice spacing would preclude the axial anomaly. In order to describe a continuum quantum field theory of Dirac fermions, lattice actions with purported exact chiral symmetry must break the flavor-singlet axial symmetry. We demonstrate that this is indeed the case by using a minimally doubled fermion action. For simplicity, we consider the Abelian axial anomaly in two dimensions. At finite lattice spacing and with gauge interactions, the axial anomaly arises from nonconservation of the flavor-singlet current. Similar nonconservation also leads to the axial anomaly in the case of the naïve lattice action. For minimally doubled actions, however, fine-tuning of the action and axial current is necessary to arrive at the anomaly. Conservation of the flavor nonsinglet vector current additionally requires the current to be fine-tuned. Finally, we determine that the chiral projection of a minimally doubled fermion action can be used to arrive at a lattice theory with an undoubled Dirac fermion possessing the correct anomaly in the continuum limit.

Rare semileptonic decays of $B$ and $B_c$ mesons are investigated in the framework of the QCD-motivated relativistic quark model based on the quasipotential approach. Form factors parametrizing the matrix elements of the weak transitions between corresponding meson states are calculated with the complete account of the relativistic effects including contributions of intermediate negative energy states and relativistic transformations of the meson wave functions. The momentum transfer dependence of the form factors is reliably determined in the whole accessible kinematical range. On this basis the total and differential branching fractions of the $B\to K^{(*)}{l}^{+}{l}^{-}(\nu \overline{\nu })$ and $B_c\to D_s^{(*)}{l}^{+}{l}^{-}(\nu \overline{\nu })$, $B_c\to D^{(*)}{l}^{+}{l}^{-}(\nu \overline{\nu })$ decays as well as the longitudinal polarization fractions $F_L$ of the final vector meson and the muon forward-backward asymmetries $A_{\mathrm{FB}}$ are calculated. Good agreement of the obtained results with the recent detailed experimental data on the $B\to K^{(*)}{\mu }^{+}{\mu }^{-}$ decays from Belle and CDF is found. Predictions for the rare semileptonic decays of the $B_c$ mesons are given.

We analyze upper limits on a possible gluon mass, $m_g$. We first discuss various ways to modify quantum chromodynamics to include $m_g\ne 0$, including a bare mass, a Higgs mechanism, and dynamical breaking of color $\mathrm{SU}(3{)}_c$. From an examination of experimental data, we infer an upper limit $m_g<\mathrm{O}(1)\mathrm{MeV}$. As part of our analysis, we show that a claim, hitherto unrefuted in the literature, of a much stronger upper limit on $m_g$, is invalid. We discuss subtleties in interpreting gluon mass limits in view of the fact that at scales below ${\Lambda }_{\mathrm{QCD}}$, quantum chromodynamics is strongly coupled, perturbation theory is not reliable, and the physics is not accurately described in terms of the Lagrangian degrees of freedom, including gluons. We also point out a fundamental difference in the behavior of quantum chromodynamics with a nonzero gluon mass and a weakly coupled gauge theory with a gauge boson mass.

With the help of the Mellin-Barnes transform, we show how to simultaneously resum the expansion of a heavy-quark correlator around $q^2=0$ (low-energy), $q^2=4m^2$ (threshold, where $m$ is the quark mass), and $q^2\to -\infty$ (high-energy) in a systematic way. We exemplify the method for the perturbative vector correlator at $\mathcal{O}({\alpha }_s^2)$ and $\mathcal{O}({\alpha }_s^3)$. We show that the coefficients, $\Omega (n)$, of the Taylor expansion of the vacuum polarization function in terms of the conformal variable $\omega$ admit, for large $n$, an expansion in powers of $1/n$ (up to logarithms of $n$) that we can calculate exactly. This large-$n$ expansion has a sign-alternating component given by the logarithms of the operator-product expansion, and a fixed-sign component given by the logarithms of the threshold expansion in the external momentum $q^2$.