Contaldi et al. [C. R. Contaldi, M. Peloso, L. Kofman, and A. Linde, J. Cosmol. Astropart. Phys. 07 (2003) 002] have suggested that an initial period of kinetic energy domination in single field inflation may explain the lack of CMB power at large angular scales. We note that in this situation it is natural that there also be a spatial gradient in the initial value of the inflaton field, and that this can provide a spatial asymmetry in the observed CMB power spectrum, manifest at low values of $\ell$. We investigate the nature of this asymmetry and comment on its relation to possible anomalies at low $\ell$.

We present counterexamples to the claim that the $\lambda {\varphi }^4$ inflaton potential is excluded by recent cosmological data. Finding counterexamples requires that the actually observed primordial fluctuations are generated at the onset of the slow-roll regime of inflation. This setup for the initial conditions is therefore different from the usual scenario of chaotic inflation where inflation starts long before the observed fluctuations are created. The primordial power spectrum of “just enough” chaotic inflation violates scale invariance in a way consistent with observations.

We study the $Z$ boson pair production mediated by the Kaluza-Klein (KK) graviton in large extra dimensions (LED) at the CERN Large Hadron Collider (LHC). We use the partial wave unitarity to discuss the constraints on the process energy scale in order to give a self-consistent calculation. We find that the LED contributions can enhance the $Z$ boson pair production cross sections significantly when the fundamental scale $M_S$ of the large extra dimensions is up to several TeV. We also show that the kinematic distributions of the LED signals are greatly different from the standard model ones and the LHC can probe the $M_S$ values up to $4.3–5.6\mathrm{TeV}$ at $3\sigma$ level depending on the number of the extra dimensions.

We have calculated the cross section of the process $e^{+}{e}^{-}\to \gamma \gamma \to b\overline{b}$ in the littlest Higgs model with $T$ parity (LHT). We find that, for the favorable parameters, the total cross section $\sigma (e^{+}{e}^{-}\to \gamma \gamma \to b\overline{b})$ is sensitive to the breaking scale $f$, mixing parameter $x_L$, the masses of the mirror quarks $m_{Hi}$, and the relative correction of the LHT model is a few percent to dozens of percent. The cross section is significantly larger than the corresponding results in the standard model and in the other typical new physics models. Therefore the prediction in the LHT model is quite different from the predictions in other new physics models and such a process is really interesting in searching for the signs of the LHT model.

In the littlest Higgs model with $T$-parity (LHT) the newly introduced mirror quarks have flavor-changing couplings with the standard model (SM) quarks and may enhance the flavor-changing neutral-current (FCNC) top-quark interactions which are extremely suppressed in the SM. In this work we perform a comprehensive study for the contributions of these mirror fermions to various top-quark FCNC decays and productions at the LHC, which includes the decays $t\to cV$ ($V=g$, $\gamma$, $Z$), $t\to cgg$ and the productions proceeding through the parton processes $cg\to t$, $gg\to t\overline{c}$, $cg\to tg$, $cg\to t\gamma$ and $cg\to tZ$. We find that although these FCNC processes can be greatly enhanced by the LHT contributions, they are hardly accessible at the LHC. Therefore, the LHT model may not cause the FCNC problem in the top-quark sector if the top-quark property is proved to be SM-like at the LHC.

In this paper we present a study of $CP$ asymmetry, single lepton polarization asymmetry and polarized $CP$ asymmetry in $B\to K^{*}{\ell }^{+}{\ell }^{-}$ decay within the four-generation standard model. Taking $|V_{t^{\prime }s}^{*}{V}_{t^{\prime }b}|=0.01$, 0.02, 0.03 with phase $\{60°–120°\}$, which is consistent with the $b\to s{\ell }^{+}{\ell }^{-}$ rate and the Bs mixing parameter $\Delta m_{\mathrm{Bs}}$, we find that $CP$ asymmetry, single lepton polarization asymmetry and polarized $CP$ asymmetry are sensitive to the existence of the fourth generation. This can serve as an indirect method to search for new physics effects, in particular, to search for the fourth-generation $\mathrm{\text{quarks}}(t^{\prime },b^{\prime })$ via their indirect manifestations in loop diagrams.

We investigate the pair production of $S$-wave heavy quarkonium at the LHC in the color-singlet mechanism (CSM) and estimate the contribution from the gluon fragmentation process in the color-octet mechanism (COM) for comparison. With the matrix elements extracted previously in the leading-order calculations, the numerical results show that the production rates are quite large for the pair production processes at the LHC. The $p_t$ distribution of double $J/\psi$ production in the CSM is dominant over that in the COM when $p_t$ is smaller than about 10 GeV. For the production of double ${\rm Y}$, the contribution of the COM is always larger than that in the CSM. The large differences in the theoretical predictions between the CSM and COM for the $p_t$ distributions in the large $p_t$ region are useful in clarifying the effects of COM on the quarkonium production. We also investigate the pair production of $S$-wave $B_c$ and $B_c^{*}$ mesons, and the measurement of these processes is useful to test the CSM and extract the long-distance matrix elements for the $B_c$ and $B_c^{*}$ mesons. Aside from numerical calculations, analytical expressions for the production differential cross sections of all these processes are also given.

Inclusive jet production data are important for constraining the gluon distribution in the global QCD analysis of parton distribution functions. With the addition of recent CDF and D0 Run II jet data, we study a number of issues that play a role in determining the up-to-date gluon distribution and its uncertainty, and produce a new set of parton distributions that make use of that data. We present in detail the general procedures used to study the compatibility between new data sets and the previous body of data used in a global fit. We introduce a new method in which the Hessian matrix for uncertainties is “rediagonalized” to obtain eigenvector sets that conveniently characterize the uncertainty of a particular observable.

We study the chiral logarithms in $\Delta S=1$ kaon decay amplitudes from new flavor physics in beyond-standard-model theories. We systematically classify the chiral structures of dimension-5, 6, and 7 effective QCD operators constructed out of light-quark (up, down, and strange) and gluon fields. Using the standard chiral perturbation theory, we calculate the leading chiral logarithms associated with these operators. The result is useful for lattice calculations of the QCD matrix elements in $K\to \pi \pi$ decay necessary, for example, to understand the physical origin of the direct $CP$ violation parameter ${ϵ}^{\prime }$. As a concrete example, we consider the new operators present in minimal left-right symmetric models.

Standard model Higgs pair production at $e^{+}{e}^{-}$ colliders has the capability to determine the Higgs boson self-coupling $\lambda$. I present a detailed analysis of the $e^{+}{e}^{-}\to ZHH$ and $e^{+}{e}^{-}\to \nu \overline{\nu }HH$ signal channels, and the relevant background processes, for future $e^{+}{e}^{-}$ linear colliders with center of mass energies of $\sqrt{s}=0.5\mathrm{TeV}$, 1 TeV, and 3 TeV. Special attention is given to the role nonresonant Feynman diagrams play, and the theoretical uncertainties of signal and background cross sections. I also derive quantitative sensitivity limits for $\lambda$. I find that an $e^{+}{e}^{-}$ collider with $\sqrt{s}=0.5\mathrm{TeV}$ can place meaningful bounds on $\lambda$ only if the Higgs boson mass is relatively close to its current lower limit. At an $e^{+}{e}^{-}$ collider with $\sqrt{s}=1\mathrm{TeV}$ (3 TeV), $\lambda$ can be determined with a precision of 20%–80% (10%–20%) for integrated luminosities in the few ${\mathrm{ab}}^{-1}$ range and Higgs boson masses in the range $m_H=120–180\mathrm{GeV}$.

This paper studies giant magnons in ${\mathrm{AdS}}_4\times C{P}^3$ using both the string sigma model and the algebraic curve. We complete the dictionary of solutions by finding the dyonic generalization of the $C{P}^1$ string solution, which matches the “small” giant magnon in the algebraic curve, and by pointing out that the solution recently constructed by the dressing method is the “big” giant magnon. We then use the curve to compute finite-$J$ corrections to all cases, which for the nondyonic cases always match the Arutyunov-Frolov-Zamaklar result. For the dyonic $R{P}^3$ magnon we recover the $S^5$ answer, but for the small and big giant magnons we obtain new corrections.

The direct sum of a couple of Maxwell-Chern-Simons gauge theories of opposite helicities $\pm 1$ does not lead to a Proca theory in $D=2+1$, although both theories share the same spectrum. However, it is known that by adding an interference term between both helicities we can join the complementary pieces together and obtain the physically expected result. A generalized soldering procedure can be defined to generate the missing interference term. Here, we show that the same procedure can be applied to join together $\pm 2$ helicity states in a full off-shell manner. In particular, by using second-order (in derivatives) self-dual models of helicities $\pm 2$ (spin-2 analogues of Maxwell-Chern-Simmons models) the Fierz-Pauli theory is obtained after soldering. Remarkably, if we replace the second-order models by third-order self-dual models (linearized topologically massive gravity) of opposite helicities, after soldering, we end up exactly with the new massive gravity theory of Bergshoeff, Hohm, and Townsend in its linearized approximation.

We study the classical and absolute stability of $Q$-balls in scalar field theories with flat potentials arising in both gravity-mediated and gauge-mediated models. We show that the associated $Q$-matter formed in gravity-mediated potentials can be stable against decay into their own free particles as long as the coupling constant of the nonrenormalizable term is small, and that all of the possible three-dimensional $Q$-ball configurations are classically stable against linear fluctuations. Three-dimensional gauge-mediated $Q$-balls can be absolutely stable in the thin-wall limit, but are completely unstable in the thick-wall limit.

We study the cosmology of a galileon scalar-tensor theory, obtained by covariantizing the decoupling Lagrangian of the Dvali-Gabadadze-Poratti (DGP) model. Despite being local in $3+1$ dimensions, the resulting cosmological evolution is remarkably similar to that of the full $4+1$-dimensional DGP framework, both for the expansion history and the evolution of density perturbations. As in the DGP model, the covariant galileon theory yields two branches of solutions, depending on the sign of the galileon velocity. Perturbations are stable on one branch and ghostlike on the other. An interesting effect uncovered in our analysis is a cosmological version of the Vainshtein screening mechanism: at early times, the galileon dynamics are dominated by self-interaction terms, resulting in its energy density being suppressed compared to matter or radiation; once the matter density has redshifted sufficiently, the galileon becomes an important component of the energy density and contributes to dark energy. We estimate conservatively that the resulting expansion history is consistent with the observed late-time cosmology, provided that the scale of modification satisfies $r_c\gtrsim 15\mathrm{Gpc}$.

Adopting the strong field limit approach, we studied the properties of strong field gravitational lensing in the deformed Hořava-Lifshitz black hole and obtained the angular position and magnification of the relativistic images. Supposing that the gravitational field of the supermassive central object of the galaxy described by this metric, we estimated the numerical values of the coefficients and observables for gravitational lensing in the strong field limit. Comparing with the Reissner-Nordström black hole, we find that with the increase of parameter $\alpha$, the angular position ${\theta }_{\infty }$ decreases more slowly and $r_m$ more quickly, but angular separation $s$ increases more rapidly. This may offer a way to distinguish a deformed Hořava-Lifshitz black hole from a Reissner-Nordström black hole by the astronomical instruments in the future.

Possible models of Yukawa interaction are discussed in the two Higgs doublet model (THDM) under the discrete symmetry imposed to avoid the flavor changing neutral current at the leading order. It is known that there are four types of such models corresponding to the possible different assignment of charges for the discrete symmetry on quarks and leptons. We first examine the decay properties of Higgs bosons in each type model, and summarize constraints on the models from current experimental data. We then shed light on the differences among these models in collider phenomenology. In particular, we mainly discuss the so-called type-II THDM and type-X THDM. The type-II THDM corresponds to the model with the same Yukawa interaction as the minimal supersymmetric standard model. On the other hand, in the type-X THDM, additional Higgs bosons can predominantly decay into leptons. This scenario may be interesting because of the motivation for a light charged Higgs boson scenario such as in the TeV-scale model of neutrinos, dark matter, and baryogenesis. We study how we can distinguish the type-X THDM from the minimal supersymmetric standard model at the Large Hadron Collider and the International Linear Collider.

The nucleon distribution amplitudes and the nucleon-to-pion transition distribution amplitudes are investigated at leading twist within the frame of a light-cone quark model. The distribution amplitudes probe the three-quark component of the nucleon light-cone wave function, while higher order components in the Fock-space expansion of the nucleon state are essential to describe the nucleon-to-pion transition distribution amplitudes. Adopting a meson-cloud model of the nucleon the nucleon-to-pion transition distribution amplitudes are calculated for the first time.

We revisited a ar you model for charmonium hybrid meson with a magnetic gluon [Yu. S. Kalashnikova and A. V. Nefediev, Phys. Rev. D 77, 054025 (2008).] and improved the numerical calculations. These improvements support the hybrid meson interpretation of $X(4260)$. Within the same model, we computed the hybrid meson mass with an electric gluon which is resolved to be lighter. Relativistic effects and coupling channels also decreased the mass.

We reconsider the question of the relative importance of single-particle effects and correlations in the solvable interacting neutrino models introduced by Friedland and Lunardini and by Bell, Rawlinson, and Sawyer. We show, by an exact calculation, that the two particle correlations are not “small,” and that they dominate the time evolution in these models, in spite of indications to the contrary from the rate of equilibration. This result holds even after the model in generalized from the original 2 flavor case to $N$ flavors. The failure of the Boltzmann single-particle approximation in this model is tentatively attributed to the simplicity of the model, in particular, to the assumption that all neutrinos in the initial state are in flavor eigenstates.