We examine the full nonlinear dynamics of closed Friedmann-Robertson-Walker universes in the framework of $D$-branes formalism. Friedmann equations contain additional terms arising from the bulk-brane interaction that provide a concrete model for nonsingular bounces in the early phase of the Universe. We construct nonsingular cosmological scenarios sourced with perfect fluids and a massive inflaton field, which are past eternal, oscillatory, and may emerge into an inflationary phase due to nonlinear resonance mechanisms. Oscillatory behavior becomes metastable when the system is driven into a resonance window of the parameter space of the models, with consequent breakup of KAM tori that trap the inflaton, leading the Universe to the inflationary regime. A construction of the resonance chart of the models is made. Resonance windows are labeled by an integer $n\ge 2$, where $n$ is related to the ratio of the frequencies in the scale factor/scalar field degrees of freedom. They are typically small compared to the volume of the whole parameter space, and we examine the constraints imposed by nonlinear resonance in the physical domain of initial configurations so that inflation may be realized. We discuss the complex dynamics arising in this preinflationary stage, the structural stability of the resonance pattern and some of its possible imprints in the physics of inflation. We also approach the issue of initial configurations that are connected to a chaotic exit to inflation. Pure scalar field bouncing cosmologies are constructed. Contrary to models with perfect fluid components, the structure of the bouncing dynamics is highly sensitive to the initial amplitude and to the mass of the inflaton; dynamical potential barriers allowing for bounces appear as a new feature of the dynamics. We argue that if our actual Universe is a brane inflated by a parametric resonance mechanism triggered by the inflaton, some observable cosmological parameters should then have a signature of the particular resonance from which the brane inflated.

The standard model (SM) plus a real gauge-singlet scalar field dubbed darkon ($\mathrm{SM}+\mathrm{D}$) is the simplest model possessing a weakly interacting massive particle (WIMP) dark-matter candidate. The upper limits for the WIMP-nucleon elastic cross section as a function of WIMP mass from the recent XENON10 and CDMS II experiments rule out darkon mass ranges from 10 to (50, 70, 75) GeV for Higgs-boson masses of (120, 200, 350) GeV, respectively. This may exclude the possibility of the darkon providing an explanation for the gamma-ray excess observed in the EGRET data. We show that by extending the $\mathrm{SM}+\mathrm{D}$ to a two-Higgs-doublet model plus a darkon the experimental constraints on the WIMP-nucleon interactions can be circumvented due to suppression occurring at some values of the product $\tan \alpha \tan \beta$, with $\alpha$ being the neutral-Higgs mixing angle and $\tan \beta$ the ratio of vacuum expectation values of the Higgs doublets. We also comment on the implication of the darkon model for Higgs searches at the LHC.

The minimal universal extra dimension (mUED) model respects the Kaluza-Klein (KK) parity $(-1{)}^n$, where $n$ is the KK number. However, it is possible to have interactions located at only one of the two fixed points of the $S_1/{\mathcal{Z}}_2$ orbifold. Such asymmetric interactions violate the KK parity. This kills the cold dark matter component of UED but also removes the upper bound on the inverse compactification radius, and thus nonobservation of the KK excitations even at the Large Hadron Collider does not necessarily invalidate the model. Apart from the decay of the lightest $n=1$ KK excitation, this leads to collider signals which are markedly different from those in the mUED scenario. The phenomenological consequences of such KK-parity violating terms are explored.

It has been recently proposed that the matter-antimatter asymmetry of the universe may have its origin in “post-sphaleron baryogenesis” (PSB). It is a TeV scale mechanism that is testable at the CERN LHC and other low energy experiments. In this paper, we present a theory of PSB within a quark-lepton unified scheme based on the gauge group $SU(2{)}_L\times SU(2{)}_R\times SU(4{)}_c$ that allows a direct connection between the baryon asymmetry and neutrino mass matrix. The flavor changing neutral current constraints on the model allow successful baryogenesis only for an inverted mass hierarchy for neutrinos, which can be tested in the proposed long base line neutrino experiments. The model also predicts observable neutron-antineutron oscillation accessible to the next generation of experiments as well as TeV scale colored scalars within reach of the LHC.

We explore the $\Delta L=2$ same-sign dilepton signal from top-quark decay via a Majorana neutrino at the LHC in the top anti-top pair production samples. The signature is same-sign dilepton plus multijets with no significant missing energy. The most optimistic region lies where the Majorana neutrino mass is between $15–65\mathrm{GeV}$. For $300{\mathrm{fb}}^{-1}$ integrated luminosity, it is possible to probe $S_{ij}$, the effective mixing parameter, to $\mathcal{O}({10}^{-5})$.

The forward limit of the chiral-odd generalized parton distributions (GPDs) and their lower moments are investigated within the framework of the chiral quark soliton model (CQSM), with particular emphasis on the transversity decomposition of nucleon angular momentum proposed by Burkardt. A strong correlation between quark spin and orbital angular momentum inside the nucleon is manifest in the derived second moment sum rule within the CQSM, thereby providing an additional support to the qualitative connection between chiral-odd GPDs and Boer-Mulders effects. We further confirm isoscalar dominance of the corresponding first moment sum rule, which indicates that the Boer-Mulders functions for the $u$ and $d$ quarks have roughly equal magnitude with the same sign. Also made are some comments on the recent empirical extraction of the tensor charges of the nucleon by Anselmino et al. We demonstrate that a comparison of their result with any theoretical predictions must be done with great care, in consideration of fairly strong scale dependence of tensor charges, especially at the lower renormalization scale.

We revisit the effect of $CP$ violating anomalous top-quark couplings in $t\overline{t}$ production and decay. We consider $t\overline{t}$ production through gluon fusion (and light $q\overline{q}$ annihilation) followed by top-quark decay into $bW$ or $b\ell \nu$. We find explicit analytic expressions for all the triple products generated by the anomalous couplings that fully incorporate all spin correlations. Our results serve as a starting point for numerical simulations for the CERN LHC.

We investigate nonstandard neutrino interactions (NSIs) in the triplet seesaw model featuring nontrivial correlations between NSI parameters and neutrino masses and mixing parameters. We show that sizable NSIs can be generated as a consequence of a nearly degenerate neutrino mass spectrum. Thus, these NSIs could lead to quite significant signals of lepton flavor violating decays such as ${\mu }^{-}\to e^{-}{\nu }_e{\overline{\nu }}_{\mu }$ and ${\mu }^{+}\to e^{+}{\overline{\nu }}_e{\nu }_{\mu }$ at a future neutrino factory, effects adding to the uncertainty in determination of the Earth matter density profile, as well as characteristic patterns of the doubly charged Higgs decays observable at the Large Hadron Collider.

We study the effect of noise on the evolution of the growth factor of density perturbations in the context of the $\Lambda \mathrm{CDM}$ model. Stochasticity is introduced as a Wiener process amplified by an intensity parameter $\alpha$. By comparing the evolution of deterministic and stochastic cases for different values of $\alpha$ we estimate the intensity level necessary to make noise relevant for cosmological tests based on large-scale structure data. Our results indicate that the presence of random forces underlying the fluid description can lead to significant deviations from the nonstochastic solution at late times for $\alpha \ge {10}^{-3}$.

We study a class of classical solutions for closed strings moving in ${\mathrm{AdS}}_3\times S^1\subset {\mathrm{AdS}}_5\times S^5$ with energy $E$ and spin $S$ in ${\mathrm{AdS}}_3$ and angular momentum $J$ and winding $m$ in $S^1$. They have rigid shape with $n$ spikes in ${\mathrm{AdS}}_3$. We find that when $J$ or $m$ are nonzero, the spikes do not end in cusps. We consider in detail a special large $n$ limit in which $S\sim n^2$, $J\sim n$, i.e. $S\gg J\gg 1$, with $\frac{E+S}{n^2}$, $\frac{E-S}{n}$, $\frac{J}{n}$, $\frac{m}{n}$ staying finite. In that limit the spiky spinning string approaches the boundary of ${\mathrm{AdS}}_5$. We show that the corresponding solution can be interpreted as describing a periodic-spike string moving in ${\mathrm{AdS}}_3–\mathrm{pp}\mathrm{\text{−}}\mathrm{\text{wave}}\times S^1$ background. The resulting expression for the string energy should represent a strong-coupling prediction for anomalous dimension of a class of dual gauge theory states in a particular thermodynamic limit of the $SL(2,R)$ spin chain.

We study jets of massless particles in $\mathcal{N}=4$ super Yang-Mills theory using the AdS/conformal field theory correspondence both at zero and finite temperature. We set up an initial state corresponding to a highly energetic quark/antiquark pair and follow its time evolution into two jets. At finite temperature the jets stop after traveling a finite distance, whereas at zero temperature they travel and spread forever. We map out the corresponding baryon number charge density and identify the generic late-time behavior of the jets as well as features that depend crucially on the initial conditions.

We discuss the criteria that must be satisfied by a well-posed variational principle. We clarify the role of Gibbons-Hawking-York type boundary terms in the actions of higher derivative models of gravity, such as $F(R)$ gravity, and argue that the correct boundary terms are the naive ones obtained through the correspondence with scalar-tensor theory, despite the fact that variations of normal derivatives of the metric must be fixed on the boundary. We show in the case of $F(R)$ gravity that these boundary terms reproduce the correct Arnowitt-Deser-Misner energy in the Hamiltonian formalism, and the correct entropy for black holes in the semiclassical approximation.

The Vaidya solution describes the gravitational collapse of a finite shell of incoherent radiation falling into flat spacetime and giving rise to a Schwarzschild black hole. There has been a question whether closed trapped surfaces can extend into the flat region (whereas closed outer trapped surfaces certainly can). For the special case of self-similar collapse we show that the answer is yes, if and only if the mass function rises fast enough.

In this paper, we consider a model of inflationary cosmology with inflation preceded by a bounce and study its primordial curvature perturbations. Our model gives rise to a primordial power spectrum with a feature of oscillation on large scales compared with the nearly scale-invariant spectrum generated by the traditional slow-rolling inflation model. This effect changes the cosmic microwave background temperature power spectrum and the large scale structure matter power spectrum. Further, with a detailed simulation we will show that in some detailed models this signal might be detectable in forthcoming observations, such as PLANCK and LAMOST.

We propose a generic framework in which the Higgs and the unparticle are both composite. The underlying theories are four-dimensional, asymptotically-free, nonsupersymmetric gauge theories with fermionic matter. We sketch a possible unification of these two sectors at a much higher scale resembling extended technicolor models. By construction our extensions are natural, meaning that there is no hierarchy problem. The coupling of the unparticle sector to the composite Higgs emerges as a four-Fermi operator. The bilinear unparticle operator near the electroweak scale has scaling dimension in the range $1<d_{\mathcal{U}}<3$. We investigate, in various ways, the breaking of scale invariance induced by the electroweak scale resulting in an unparticle condensate. The latter acts as a natural infrared cutoff or hadronic scale. We give the low-energy effective theory valid near the electroweak scale. The unparticle-Higgs mixing is found to be suppressed within our framework.

One of the simplest extensions of the standard model that explains the observed abundance of dark matter is the inert doublet model. In this theory a discrete symmetry ensures that the neutral component of an additional electroweak doublet scalar is stable and constitutes a dark matter candidate. As massive bodies such as the Sun and Earth move through the dark matter halo, dark matter particles can become gravitationally trapped in their cores. Annihilations of these particles result in neutrinos, which can potentially be observed with neutrino telescopes. We calculate the neutrino detection rate at these experiments from inert doublet dark matter annihilations in the cores of the Sun and the Earth.

Top quarks may be produced in large numbers in association with new physics at the LHC. The polarization of these top quarks probes the chiral structure of the new physics. We discuss several kinematic distributions which are sensitive to the polarization of single top quarks and can be used without full event reconstruction. For collimated tops we construct polarization-sensitive observables for both hadronic and leptonic decay modes and plot their distributions. We compute the observable polarization signals from top quarks produced in the on-shell cascade decay of a stop squark into a top quark and a neutralino, as well as top quarks produced in the analogous decay chain in same-spin partner models.

We recently derived an explicit expression for the gluon distribution function $G(x,Q^2)=xg(x,Q^2)$ in terms of the proton structure function $F_2^{\gamma p}(x,Q^2)$ in leading-order (LO) QCD by solving the LO Dokshitzer-Gribov-Lipatov-Altarelli-Parisi equation for the $Q^2$ evolution of $F_2^{\gamma p}(x,Q^2)$ analytically, using a differential-equation method. We showed that accurate experimental knowledge of $F_2^{\gamma p}(x,Q^2)$ in a region of Bjorken $x$ and virtuality $Q^2$ is all that is needed to determine the gluon distribution in that region. We rederive and extend the results here using a Laplace-transform technique, and show that the singlet quark structure function $F_{\mathrm{S}}(x,Q^2)$ can be determined directly in terms of $G$ from the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi gluon evolution equation. To illustrate the method and check the consistency of existing LO quark and gluon distributions, we used the published values of the LO quark distributions from the CTEQ5L and MRST2001 LO analyses to form $F_2^{\gamma p}(x,Q^2)$, and then solved analytically for $G(x,Q^2)$. We find that the analytic and fitted gluon distributions from MRST2001LO agree well with each other for all $x$ and $Q^2$, while those from CTEQ5L differ significantly from each other for large $x$ values, $x\gtrsim 0.03–0.05$, at all $Q^2$. We conclude that the published CTEQ5L distributions are incompatible in this region. Using a nonsinglet evolution equation, we obtain a sensitive test of quark distributions which holds in both LO and next-to-leading order perturbative QCD. We find in either case that the CTEQ5 quark distributions satisfy the tests numerically for small $x$, but fail the tests for $x\gtrsim 0.03–0.05$—their use could potentially lead to significant shifts in predictions of quantities sensitive to large $x$. We encountered no problems with the MRST2001LO distributions or later CTEQ distributions. We suggest caution in the use of the CTEQ5 distributions.

We obtain explicitly the renormalization group equations for the quark mass matrices in terms of a set of rephasing invariant parameters. For a range of assumed high energy values for the mass ratios and mixing parameters, they are found to evolve rapidly and develop hierarchies as the energy scale decreases. To achieve the experimentally observed high degree of hierarchy, however, the introduction of new models with specific properties becomes necessary.

Extending the standard model with three right-handed neutrinos ($N_k$) and a second Higgs doublet ($\eta$), odd under the discrete parity symmetry $Z_2$, Majorana neutrino masses can be generated at one-loop order. In the resulting model, the lightest stable particle, either a boson or a fermion, might be a dark matter candidate. Here we assume a specific mass spectrum ($M_1\ll M_2<M_3<m_{\eta }$) and derive its consequences for dark matter and collider phenomenology. We show that (i) the lightest right-handed neutrino is a warm dark matter particle that can give a $\sim 10\%$ contribution to the dark matter density; (ii) several decay branching ratios of the charged scalar can be predicted from measured neutrino data. Especially interesting is that large lepton flavor violating rates in muon and tau final states are expected. Finally, we derive upper bounds on the right-handed neutrino Yukawa couplings from the current experimental limit on $Br(\mu \to e\gamma )$.