Quantum singularities considered in the $3D$ Banados-Teitelboim-Zanelli (BTZ) spacetime by Pitelli and Letelier [Phys. Rev. D 77, 124030 (2008)] is extended to charged BTZ and $3D$ Einstein-Maxwell-dilaton gravity spacetimes. The occurrence of naked singularities in the Einstein-Maxwell extension of the BTZ spacetime both in linear and nonlinear electrodynamics as well as in the Einstein-Maxwell-dilaton gravity spacetimes are analyzed with the quantum test fields obeying the Klein-Gordon and Dirac equations. We show that with the inclusion of the matter fields, the conical geometry near $r=0$ is removed and restricted classes of solutions are admitted for the Klein-Gordon and Dirac equations. Hence, the classical central singularity at $r=0$ turns out to be quantum mechanically singular for quantum particles obeying the Klein-Gordon equation but nonsingular for fermions obeying the Dirac equation. Explicit calculations reveal that the occurrence of the timelike naked singularities in the considered spacetimes does not violate the cosmic censorship hypothesis as far as the Dirac fields are concerned. The role of horizons that clothes the singularity in the black hole cases is replaced by repulsive potential barrier against the propagation of Dirac fields.

When analyzing a system consisting of both dark matter and dark energy, an often used practice in the literature is to neglect the perturbations in the dark energy component. However, it has recently been argued, through the use of numerical simulations, that one cannot do so. In this work we show that by neglecting such perturbations one is implicitly making a choice of gauge. As such, one no longer has the freedom to choose, for example, a gauge comoving with the dark matter—in fact doing so will give erroneous, gauge dependent results. We obtain results consistent with the numerical simulations by using the formalism of cosmological perturbation theory, and thus without resorting to involved numerical calculations.

We study radion stabilization in the compact Randall-Sundrum model by introducing a bulk scalar field, as in the Goldberger and Wise mechanism, but (partially) taking into account the backreactions from the scalar field on the metric. Our generalization reconciles the radion potential found by Goldberger and Wise with the radion mass obtained with the so-called superpotential method where backreaction is fully considered. Moreover we study the holographic phase transition and its gravitational wave signals in this model. The improved control over backreactions opens up a large region in parameter space and leads, compared to former analysis, to weaker constraints on the rank $N$ of the dual gauge theory. We conclude that, in the regime where the $1/N$ expansion is justified, the gravitational wave signal is detectable by LISA.

We investigate the virialization of cosmic structures in the framework of flat Friedmann-Lemaitre-Robertson-Walker cosmological models, in which the vacuum energy density evolves with time. In particular, our analysis focuses on the study of spherical matter perturbations, as they decouple from the background expansion, “turn around,” and finally collapse. We generalize the spherical collapse model in the case when the vacuum energy is a running function of the Hubble rate, $\Lambda =\Lambda (H)$. A particularly well-motivated model of this type is the so-called quantum field vacuum, in which $\Lambda (H)$ is a quadratic function, $\Lambda (H)=n_0+n_2{H}^2$, with $n_0\ne 0$. This model was previously studied by our team using the latest high quality cosmological data to constrain its free parameters, as well as the predicted cluster formation rate. It turns out that the corresponding Hubble expansion history resembles that of the traditional $\Lambda \mathrm{CDM}$ cosmology. We use this $\Lambda (t)\mathrm{CDM}$ framework to illustrate the fact that the properties of the spherical collapse model (virial density, collapse factor, etc.) depend on the choice of the considered vacuum energy (homogeneous or clustered). In particular, if the distribution of the vacuum energy is clustered, then, under specific conditions, we can produce more concentrated structures with respect to the homogeneous vacuum energy case.

The inclusive same-sign dilepton channel is already recognized as a promising discovery signature for supersymmetry in the early days of the LHC. We point out that it can also be used for precision measurements of sparticle masses after the initial discovery. As an illustration, we consider the LM6 CMS study point in minimal supergravity, where the same-sign leptons most often result from chargino decays to sneutrinos. We discuss three different techniques for determining the chargino and sneutrino masses in an inclusive manner, i.e., using only the two well measured lepton momenta, while treating all other upstream objects in the event as a single entity of total transverse momentum ${\overrightarrow{P}}_T$. This approach takes full advantage of the large production rates of colored superpartners, but does not rely on the poorly measured hadronic jets, and avoids any jet combinatorics problems.

We update our estimates of charged and neutral current neutrino total cross sections on isoscalar nucleons at ultrahigh energies using a global ($x$, $Q^2$) fit, motivated by the Froissart bound, to the $F_2$ (electron-proton) structure function utilizing the most recent analysis of the complete ZEUS and H1 data sets from HERA I. We compare both to our previous work, which utilized only the smaller ZEUS data set, as well as to recent results of a calculation using the ZEUS-S based global perturbative QCD parton distributions using the combined HERA I results as input. Our new results substantiate our previous conclusions, again predicting significantly smaller cross sections than those predicted by extrapolating pQCD calculations to neutrino energies above ${10}^9\mathrm{GeV}$.

The D0 Collaboration has reported an excess of roughly 1% of ${\mu }^{-}{\mu }^{-}$ pairs over ${\mu }^{+}{\mu }^{+}$ pairs in $\overline{p}p$ collisions at a center-of-mass energy $\sqrt{s}=1.96\mathrm{GeV}$ at the Fermilab Tevatron, when known backgrounds are subtracted. This excess, if ascribed to $CP$ violation in meson-antimeson mixing of nonstrange or strange neutral $B$ mesons, is about 40 times that expected in the standard model. We propose a null test, based on a tight restriction on the muon impact parameter $b$, to confirm that this excess is indeed due to $B$ mesons. If the asymmetry is due to anomalous $CP$ violation in $B_s$-${\overline{B}}_s$ mixing, then a tight restriction on $b$ would increase by a factor 2 the net asymmetry from neutral $B$ mixing, while the sample of dimuons from neutral $B$ decays will be reduced significantly relative to background events.

We present a detailed phenomenological analysis of single-inclusive hadron production at the CERN-LHC in both proton-proton and proton-lead collisions. First data from the LHC experiments on charged hadron spectra are compared to next-to-leading order QCD expectations, and predictions are made for identified pion, kaon, and proton distributions differential in transverse momentum and rapidity for LHC energies from 900 GeV to 14 TeV. The results are obtained with the latest sets of vacuum fragmentation functions based on global QCD analyses, and recently proposed medium modified fragmentation functions are used to model hadronization in proton-lead collisions assuming standard QCD factorization. Besides estimating theoretical ambiguities due to the choice of factorization and renormalization scales and parton densities, we carefully assess uncertainties due to our present knowledge of parton-to-hadron fragmentation functions with the Lagrange multiplier technique. It is outlined to what extent future LHC data will contribute to further our quantitative understanding of hadronization processes.

We propose an $A_4$ flavor-symmetric $\mathrm{SU}(3)\otimes \mathrm{SU}(2)\otimes \mathrm{U}(1)$ seesaw model where lepton number is broken spontaneously. A consistent two-zero texture pattern of neutrino masses and mixing emerges from the interplay of type-I and type-II seesaw contributions, with important phenomenological predictions. We show that, if the Majoron becomes massive, such seesaw scenario provides a viable candidate for decaying dark matter, consistent with cosmic microwave background lifetime constraints that follow from current WMAP observations. We also calculate the subleading one-loop-induced decay into photons which leads to a monoenergetic emission line that may be observed in future x-ray missions such as Xenia.

An underwater acoustic sensor array spanning $\sim 1500{\mathrm{km}}^3$ is used to search for cosmic-ray neutrinos of ultrahigh energies ( $E_{\nu }>{10}^{18}\mathrm{eV}$). Approximately 328 million triggers accumulated over an integrated 130 days of data taking are analyzed. The sensitivity of the experiment is determined from a Monte Carlo simulation of the array using recorded noise conditions and expected waveforms. Two events are found to have properties compatible with showers in the energy range ${10}^{24}\mathrm{eV}<E_{\mathrm{sh}}<5\times {10}^{24}\mathrm{eV}$ and ${10}^{22}\mathrm{eV}<E_{\mathrm{sh}}<5\times {10}^{22}\mathrm{eV}$. Since the understanding of impulsive backgrounds is limited, a flux upper limit is set providing the most sensitive limit on ultrahigh energy neutrinos using the acoustic technique.

Detailed calculations of the complete $\mathcal{O}({\alpha }_s)$ corrections to the top-quark decay widths $\Gamma (t\to q+V)$ with $V=g$, $\gamma$, $Z$, and $q=u$, $c$ are presented. Besides describing in detail the calculations in our previous work [Phys. Rev. Lett. 102, 072001 (2009)], we also include the mixing effects of the flavor-changing neutral-current operators for $t\to q+\gamma$ and $t\to q+Z$, which were not considered previously. We show that the mixing effects can either be large or small depending on the values of various anomalous couplings and thereby increase or decrease the branching ratios for $t\to q+\gamma$ and $t\to q+Z$.

We analyze the existence of a dilaton in gauge theories with approximate infrared conformal symmetry. To the extent that these theories are governed in the infrared by an approximate fixed point (walking), the explicit breaking of the conformal symmetry at these scales is vanishingly small. If confinement and spontaneous chiral-symmetry breaking set in at some infrared scale, the resultant breaking of the approximate conformal symmetry can lead to the existence of a dilaton with mass parametrically small compared to the confinement scale, and potentially observable at the LHC.

Eigenmodes of the electromagnetic field with perfectly conducting or infinitely permeable conditions on the boundary of a $D$-dimensional spherically symmetric cavity is derived explicitly. It is shown that there are ($D-2$) polarizations for TE modes and one polarization for TM modes, giving rise to a total of ($D-1$) polarizations. In case of a $D$-dimensional ball, the eigenfrequencies of the electromagnetic field with perfectly conducting boundary condition coincides with the eigenfrequencies of gauge 1-forms with relative boundary condition; whereas the eigenfrequencies of the electromagnetic field with infinitely permeable boundary condition coincides with the eigenfrequencies of gauge 1-forms with absolute boundary condition. Casimir energies of single and concentric spherical shells in $D$-dimensions are computed. The Casimir energy of concentric spherical shells can be written as a sum of the single spherical shell contributions and an interacting term, and the latter is free of divergence. The interacting term always gives rise to an attractive force between the two spherical shells. Its leading term is the Casimir force acting between two parallel plates of the same area, as expected by proximity force approximation.

We study isotropic and anisotropic (Bianchi I) cosmologies in Palatini $f(R)$ and $f(R,R_{\mu \nu }{R}^{\mu \nu })$ theories of gravity with a perfect fluid and consider the existence of nonsingular bouncing solutions in the early universe. We find that all $f(R)$ models with isotropic bouncing solutions develop shear singularities in the anisotropic case. On the contrary, the simple quadratic model $R+a{R}^2/R_P+R_{\mu \nu }{R}^{\mu \nu }/R_P$ exhibits regular bouncing solutions in both isotropic and anisotropic cases for a wide range of equations of state, including dust (for $a<0$) and radiation (for arbitrary $a$). It thus represents a purely gravitational solution to the big bang singularity and anisotropy problems of general relativity without the need for exotic ($w>1$) sources of matter/energy or extra degrees of freedom.

We show that all eccentric timelike orbits in Reissner-Nordström spacetime can be classified using a taxonomy that draws upon an isomorphism between periodic orbits and the set of rational numbers. By virtue of the fact that the rationals are dense, the taxonomy can be used to approximate aperiodic orbits with periodic orbits. This may help reduce computational overhead for calculations in gravitational wave astronomy. Our dynamical systems approach enables us to study orbits for both charged and uncharged particles in spite of the fact that charged particle orbits around a charged black hole do not admit a simple one-dimensional effective potential description. Finally, we show that comparing periodic orbits in the Reissner-Nordström and Schwarzschild geometries enables us to distinguish charged and uncharged spacetimes by looking only at the orbital dynamics.

Using the most general form of the interpolating currents, the coupling constants $g_{{\Sigma }_b{\Sigma }_b\pi }$ and $g_{{\Sigma }_c{\Sigma }_c\pi }$ are calculated within the light cone QCD sum rules approach. It is found that $g_{{\Sigma }_c{\Sigma }_c\pi }=-8.0\pm 1.7$ and $g_{{\Sigma }_b{\Sigma }_b\pi }=-11.0\pm 2.1$.

We perform a comprehensive study of the Higgs sector in the framework of the next-to-minimal supersymmetric standard model with $CP$-violating parameters in the superpotential and in the soft-supersymmetry-breaking sector. Since the $CP$ is no longer a good symmetry, the two $CP$-odd and the three $CP$-even Higgs bosons of the next-to-minimal supersymmetric standard model in the $CP$-conserving limit will mix. We show explicitly how the mass spectrum and couplings to gauge bosons of the various Higgs bosons change when the $CP$-violating phases take on nonzero values. We include full one-loop and the logarithmically enhanced two-loop effects employing the renormalization-group (RG) improved approach. In addition, the LEP limits, the global minimum condition, and the positivity of the square of the Higgs-boson mass have been imposed. We demonstrate the effects on the Higgs-mass spectrum and the couplings to gauge bosons with and without the RG-improved corrections. Substantial modifications to the allowed parameter space happen because of the changes to the Higgs-boson spectrum and their couplings with the RG-improved corrections. Finally, we calculate the mass spectrum and couplings of the few selected scenarios and compare to the previous results in literature where possible; in particular, we illustrate a scenario motivated by electroweak baryogenesis.

We report results from an updated study of the suppressed decays $B^{-}\to D{K}^{-}$ and $B^{-}\to D^{*}{K}^{-}$ followed by $D\to K^{+}{\pi }^{-}$, where $D^{(*)}$ indicates a $D^{(*)0}$ or a ${\overline{D}}^{(*)0}$ meson, and $D^{*}\to D{\pi }^0$ or $D^{*}\to D\gamma$. These decays are sensitive to the Cabibbo-Kobayashi-Maskawa unitarity triangle angle $\gamma$ due to interference between the $b\to c$ transition $B^{-}\to D^{(*)0}{K}^{-}$ followed by the doubly Cabibbo-suppressed decay $D^0\to K^{+}{\pi }^{-}$, and the $b\to u$ transition $B^{-}\to {\overline{D}}^{(*)0}{K}^{-}$ followed by the Cabibbo-favored decay ${\overline{D}}^0\to K^{+}{\pi }^{-}$. We also report an analysis of the decay $B^{-}\to D^{(*)}{\pi }^{-}$ with the $D$ decaying into the doubly Cabibbo-suppressed mode $D\to K^{+}{\pi }^{-}$. Our results are based on $467\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at SLAC. We measure the ratios ${\mathcal{R}}^{(*)}$ of the suppressed ($[K^{+}{\pi }^{-}{]}_D{K}^{-}/{\pi }^{-}$) to favored ($[K^{-}{\pi }^{+}{]}_D{K}^{-}/{\pi }^{-}$) branching fractions as well as the $CP$ asymmetries ${\mathcal{A}}^{(*)}$ of those modes. We see indications of signals for the $B^{-}\to D{K}^{-}$ and $B^{-}\to D_{D{\pi }^0}^{*}{K}^{-}$ suppressed modes, with statistical significances of 2.1 and $2.2\sigma$, respectively, and we measure: ${\mathcal{R}}_{DK}=(1.1\pm 0.6\pm 0.2)\times {10}^{-2},{\mathcal{A}}_{DK}=-0.86\pm {0.47}_{-0.16}^{+0.12}$, ${\mathcal{R}}_{(D{\pi }^0)K}^{*}=(1.8\pm 0.9\pm 0.4)\times {10}^{-2},{\mathcal{A}}_{(D{\pi }^0)K}^{*}=+0.77\pm 0.35\pm 0.12,{\mathcal{R}}_{(D\gamma )K}^{*}=(1.3\pm 1.4\pm 0.8)\times {10}^{-2},{\mathcal{A}}_{(D\gamma )K}^{*}=+0.36\pm {0.94}_{-0.41}^{+0.25}$, where the first uncertainty is statistical and the second is systematic. We use a frequentist approach to obtain the magnitude of the ratio $r_B\equiv |A(B^{-}\to {\overline{D}}^0{K}^{-})/A(B^{-}\to D^0{K}^{-})|=({9.5}_{-4.1}^{+5.1})\%$, with $r_B<16.7\%$ at 90% confidence level. In the case of $B^{-}\to D^{*}{K}^{-}$ we find $r_B^{*}\equiv |A(B^{-}\to {\overline{D}}^{*0}{K}^{-})/A(B^{-}\to D^{*0}{K}^{-})|=({9.6}_{-5.1}^{+3.5})\%$, with $r_B^{*}<15.0\%$ at 90% confidence level.

We present measurements of $B^{+}\to {\overline{D}}^{*0}{\tau }^{+}{\nu }_{\tau }$ and $B^{+}\to {\overline{D}}^0{\tau }^{+}{\nu }_{\tau }$ decays in a data sample of $657\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB asymmetric-energy $e^{+}{e}^{-}$ collider. We find ${446}_{-56}^{+58}$ $B^{+}\to {\overline{D}}^{*0}{\tau }^{+}{\nu }_{\tau }$ events with a significance of 8.1 standard deviations, and ${146}_{-41}^{+42}$ $B^{+}\to {\overline{D}}^0{\tau }^{+}{\nu }_{\tau }$ events with a significance of 3.5 standard deviations. The latter signal provides the first evidence for this decay mode. The measured branching fractions are $\mathcal{B}(B^{+}\to {\overline{D}}^{*0}{\tau }^{+}{\nu }_{\tau })=({2.12}_{-0.27}^{+0.28}(\mathrm{stat})\pm 0.29(\mathrm{syst}))\%$ and $\mathcal{B}(B^{+}\to {\overline{D}}^0{\tau }^{+}{\nu }_{\tau })=(0.77\pm 0.22(\mathrm{stat})\pm 0.12(\mathrm{syst}))\%$.