The charge radii of octet-baryons obtained in quenched lattice-QCD calculations are extrapolated within heavy-baryon chiral perturbation theory. Finite-range regularization is applied to improve the convergence of the chiral expansion and to provide estimates of quenching artifacts. Lattice values of quark distribution radii and baryon charge radii for $m_{\pi }^2$ in the range $(0.1,0.7){\mathrm{GeV}}^2$ are described very well with finite-range regularization. Upon estimating corrections for both finite-volume and quenching effects, the obtained charge radii of the proton, neutron and ${\Sigma }^{-}$ are in good agreement with experimental measurements. The predicted charge radii of the remaining octet-baryons have not yet been measured and present a challenge to future experiments.

In this paper, we construct Euclidean instanton and wormhole solutions in $d=4$, $N=2$ supergravity theories with hypermultiplets. The analytic continuation of the hypermultiplet action, involving pseudoscalar axions, is discussed using the approach originally developed by Coleman, which determines the appearance of boundary terms. In particular, we investigate the conditions obtained by requiring the action to be positive definite once the boundary terms are taken into account. The case of two hypermultiplets parameterizing the coset $G_{2,2}/SU(2)\times SU(2)$ is studied in detail. Orientifold projections that reduce the supersymmetry to $N=1$ are also discussed.

In this work we study localization of a Kalb-Ramond tensorial gauge field on a membrane described by real scalar fields. The membrane is embedded in an AdS-type five-dimensional bulk space, which mimics a Randall-Sundrum scenario. First, we consider a membrane described by only a single real scalar field. In that scenario we find that there is no localized tensorial zero mode. When we take into account branes described by two real scalar fields with internal structures, we obtain again a nonlocalized zero mode for a Kalb-Ramond tensorial gauge field. After modifying our model of one single scalar field by coupling the dilaton to the Kalb-Ramond field, we find that this result is changed. Furthermore, we analyze Kaluza-Klein massive modes and resonance structures.

The low-energy limit of string theory contains an anomaly-canceling correction to the Einstein-Hilbert action, which defines an effective theory: Chern-Simons (CS) modified gravity. The CS correction consists of the product of a scalar field with the Pontryagin density, where the former can be treated as a background field (nondynamical formulation) or as an evolving field (dynamical formulation). Many solutions of general relativity persist in the modified theory; a notable exception is the Kerr metric, which has sparked a search for rotating black hole solutions. Here, for the first time, we find a solution describing a rotating black hole within the dynamical framework, and in the small-coupling/slow-rotation limit. The solution is axisymmetric and stationary, constituting a deformation of the Kerr metric with dipole scalar “hair,” whose effect on geodesic motion is to weaken the frame-dragging effect and shift the location of the innermost stable circular orbit outwards (inwards) relative to Kerr for corotating (counterrotating) geodesics. We further show that the correction to the metric scales inversely with the fourth power of the radial distance to the black hole, suggesting it will escape any meaningful bounds from weak-field experiments. For example, using binary pulsar data we can only place an initial bound on the magnitude of the dynamical coupling constant of ${\xi }^{1/4}\lesssim {10}^4\mathrm{km}$. More stringent bounds will require observations of inherently strong-field phenomena.

The recently introduced Sommerfeld enhancement of the dark matter annihilation cross section has important implications for the detection of dark matter annihilation in subhalos in the Galactic halo. In addition to the boost to the dark matter annihilation cross section from the high densities of these subhalos with respect to the main halo, an additional boost caused by the Sommerfeld enhancement results from the fact that they are kinematically colder than the Galactic halo. If we further believe the generic prediction of the cold dark matter paradigm that in each subhalo there is an abundance of substructure which is approximately self-similar to that of the Galactic halo, then I show that additional boosts coming from the density enhancements of these small substructures and their small velocity dispersions enhance the dark matter annihilation cross section even further. I find that very large boost factors (${10}^5$ to ${10}^9$) are obtained in a large class of models. The implications of these boost factors for the detection of dark matter annihilation from dwarf spheroidal galaxies in the Galactic halo are such that, generically, they outshine the background gamma-ray flux and are detectable by the Fermi Gamma-ray Space Telescope.

The emission from neutral hydrogen (HI) clouds in the post-reionization era ($z\le 6$), too faint to be individually detected, is present as a diffuse background in all low frequency radio observations below 1420 MHz. The angular and frequency fluctuations of this radiation ($\sim 1\mathrm{mK}$) are an important future probe of the large-scale structures in the Universe. We show that such observations are a very effective probe of the background cosmological model and the perturbed Universe. In our study we focus on the possibility of determining the redshift-space distortion parameter $\beta$, coordinate distance $r_{\nu }$, and its derivative with redshift $r_{\nu }^{\prime }$. Using reasonable estimates for the observational uncertainties and configurations representative of the ongoing and upcoming radio interferometers, we predict parameter estimation at a precision comparable with supernova Ia observations and galaxy redshift surveys, across a wide range in redshift that is only partially accessed by other probes. Future HI observations of the post-reionization era present a new technique, complementing several existing ones, to probe the expansion history and to elucidate the nature of the dark energy.

We systematically explore the parameter space of the state-of-the-art brane-antibrane inflation model (Baumann et al., arXiv:0706.0360, arXiv:0705.3837) which is one of the most rigorously derived from string theory, applying the cosmic background explorer normalization and constraint on the spectral index. We improve on previous treatments of uplifting by antibranes and show that the contributions from noninflationary throats play an important role in achieving a flat inflationary potential. To quantify the degree of fine-tuning needed by the model, we define an effective volume in the part of parameter space which is consistent with experimental constraints, and using Monte Carlo methods to search for a set of optimal parameters, we show that the degree of fine-tuning is alleviated by 8 orders of magnitude relative to a fiducial point which has previously been considered. In fact, close to the optimal parameter values, fine-tuning is no longer needed for any of the parameters. We show that in this natural region of the parameter space, larger values of $n_s$ close to 0.99 (still within $2\sigma$ of the WMAP5 central value) are favored, giving a new aspect of testability to the model.

In this work, we studied how the relative variation of the gravitational constant $|\dot{\overline{G}}/\overline{G}{|}_0$ at the redshift $z=0$ restricts model parameters in Palatini $f(R)$ gravity. According to results from the observation of big bang nucleosynthesis and the anisotropies in the cosmic microwave background radiation, the ratio that gives the general constraint condition on the $f(R)$ model is taken to be $|\dot{\overline{G}}/\overline{G}{|}_0<{10}^{-13}{\mathrm{yr}}^{-1}$. Associating with the scalar curvature at present, this constraint condition yields concrete relations among model parameters in the generalized $\Lambda \mathrm{CDM}$ model, the logarithmic Lagrangian, and the exponential gravity model. These constraint relations which can be reconcilable with the value $|\dot{\overline{G}}/\overline{G}{|}_0<{10}^{-13}{\mathrm{yr}}^{-1}$ are plotted.

Using lattice simulations, we study the extent of the conformal window for an SU(3) gauge theory with $N_f$ Dirac fermions in the fundamental representation. We extend our recently reported work, describing the general framework and the lattice simulations in more detail. We find that the theory is conformal in the infrared for $N_f=12$, governed by an infrared fixed point, whereas the $N_f=8$ theory exhibits confinement and chiral symmetry breaking. We therefore conclude that the low end of the conformal window $N_f^{\mathrm{c}}$ lies in the range $8\le N_f^{\mathrm{c}}\le 12$. We discuss open questions and the potential relevance of the present work to physics beyond the standard model.

We study extensions of the standard model with a strongly coupled fourth generation. This occurs in models where electroweak symmetry breaking is triggered by the condensation of at least some of the fourth-generation fermions. With focus on the phenomenology at the LHC, we study the pair production of fourth-generation down quarks, $D_4$. We consider the typical masses that could be associated with a strongly coupled fermion sector, in the range (300–600) GeV. We show that the production and successive decay of these heavy quarks into final states with same-sign dileptons, trileptons, and four leptons can be easily seen above background with relatively low luminosity. On the other hand, in order to confirm the presence of a new strong interaction responsible for fourth-generation condensation, we study its contribution to $D_4$ pair production, and the potential to separate it from standard QCD-induced heavy quark production. We show that this separation might require large amounts of data. This is true even if it is assumed that the new interaction is mediated by a massive colored vector boson, since its strong coupling to the fourth generation renders its width of the order of its mass. We conclude that, although this class of models can be falsified at early stages of the LHC running, its confirmation would require high integrated luminosities.

We calculate the vacuum polarization functions on the lattice using the overlap fermion formulation. By matching the lattice data at large momentum scales with the perturbative expansion supplemented by the operator product expansion (OPE), we extract the strong coupling constant ${\alpha }_s(\mu )$ in two-flavor QCD as ${\Lambda }_{\overline{MS}}^{(2)}=0.234(9)(\genfrac{}{}{0ex}{}{+16}{-0})\mathrm{GeV}$, where the errors are statistical and systematic, respectively. In addition, from the analysis of the difference between the vector and axial-vector channels, we obtain some of the four-quark condensates.

We have used the chiral-quark soliton model formulated in the infinite momentum frame to investigate the octet, decuplet, and antidecuplet tensor charges up to the $5Q$ sector. Using flavor $SU(3)$ symmetry we have obtained for the proton $\delta u=1.172$ and $\delta d=-0.315$ in fair agreement with previous model estimations. The $5Q$ contribution allowed us to estimate also the strange contribution to the proton tensor charge $\delta s=-0.011$. All those values have been obtained at the model scale $Q_0^2=0.36{\mathrm{GeV}}^2$.

The radiative and leptonic decays of ${\eta }_c\to \gamma \gamma$ and ${\eta }_c\to l^{+}{l}^{-}$ are studied. For a ${\eta }_c\to \gamma \gamma$ decay, the second-order electromagnetic tree-level diagram gives the leading contribution. The decay rate of ${\eta }_c\to \gamma \gamma$ is calculated, the prediction is in good agreement with the experimental data. For ${\eta }_c\to l^{+}{l}^{-}$, both the tree and loop diagrams are calculated. The analysis shows that the loop contribution dominates; the contribution of tree diagram with a $Z^0$ intermediate state can only modify the decay rate by less than 1%. The prediction of the branching ratios of ${\eta }_c\to e^{+}{e}^{-}$ and ${\mu }^{+}{\mu }^{-}$ are very tiny within the standard model. The smallness of these predictions within the standard model makes the leptonic decays of ${\eta }_c$ sensitive to physics beyond the standard model. Measurement of the leptonic decay may give information about new physics.

We study the $\sigma$ meson in QCD sum rules using a two-quark interpolating field with derivatives. In the constituent quark model, the $\sigma$ meson is composed of a quark and an antiquark in the relative $p$-wave state and is thus expected to have a larger overlap with an interpolating field that measures the derivative of the relative quark wave function. While the sum rule with a current without derivative gives a pole mass of around 1 GeV, the present sum rule with derivative current gives a mass of around 550 MeV and a width of 400 MeV, that could be identified with the $\sigma$ meson.

We search for a consistent view on the RUNJOB experiment and present an alternative analysis based on explicitly reported and published numerical data. Here we show that there is more than one interpretation to the reported observational data. It is demonstrated that, contrary to the wide-spread opinion, the RUNJOB data are not inconsistent with an increase of the average mass near the knee region of the cosmic ray spectrum. Considering very low statistics and systematic uncertainties, especially in the high energy region, we suggest that peculiarities of the methodical origin were the most likely source of those RUNJOB conclusions which contradicted previous observations reported by other groups.

We present a measurement of the top quark mass in the all hadronic channel ($t\overline{t}\to b\overline{b}{q}_1{\overline{q}}_2{q}_3{\overline{q}}_4$) using $943{\mathrm{pb}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ collected at the CDF II detector at Fermilab (CDF). We apply the standard model production and decay matrix element (ME) to $t\overline{t}$ candidate events. We calculate per-event probability densities according to the ME calculation and construct template models of signal and background. The scale of the jet energy is calibrated using additional templates formed with the invariant mass of pairs of jets. These templates form an overall likelihood function that depends on the top quark mass and on the jet energy scale (JES). We estimate both by maximizing this function. Given 72 observed events, we measure a top quark mass of $171.1\pm 3.7(\mathrm{stat}+\mathrm{JES})\pm 2.1(\mathrm{syst})\mathrm{GeV}/c^2$. The combined uncertainty on the top quark mass is $4.3\mathrm{GeV}/c^2$.

We report on a search for the $X(1812)$ state in the decay $B^{\pm }\to K^{\pm }\omega \varphi$ with a data sample of $657\times {10}^6$ $B\overline{B}$ pairs collected with the Belle detector at the KEKB $e^{+}{e}^{-}$ collider. No significant signal is observed. An upper limit $\mathcal{B}(B^{\pm }\to K^{\pm }X(1812),X(1812)\to \omega \varphi )<3.2\times {10}^{-7}$ (90% C.L.) is determined. We also constrain the three-body decay branching fraction to be $\mathcal{B}(B^{\pm }\to K^{\pm }\omega \varphi )<1.9\times {10}^{-6}$ (90% C.L.).

We consider four-derivative corrections to the bosonic sector of five-dimensional $\mathcal{N}=2$ gauged supergravity. Since this theory includes the $\mathcal{N}=2$ graviphoton, we consider both curvature and graviphoton field-strength terms that show up at the four-derivative level. We construct, to linear order, the higher-derivative corrections to the nonrotating $R$-charged ${\mathrm{AdS}}_5$ black hole and demonstrate how this solution transforms under field redefinitions.

We calculate analytically greybody factors of Schwarzschild black holes localized on a 3-brane of finite tension and codimension 2. We obtain explicit expressions for various types of particles emitted in the bulk as well as on the brane in both the low- and high-frequency regimes. In the latter case, we obtain expressions which are valid for an arbitrary number of extra dimensions if the brane tension vanishes.