A scenario is investigated in which the leading-twist pion distribution amplitude ${\phi }_{\pi }(x)$ is approximated by the pion decay constant $f_{\pi }$ for all essential values of the light-cone fraction $x$. A model for the light-front wave function $\Psi (x,k_{\perp })$ is proposed that produces such a distribution amplitude and has a rapidly decreasing (exponential for definiteness) dependence on the light-front energy combination $k_{\perp }^2/x(1-x)$. It is shown that this model easily reproduces the fit of recent large-$Q^2$ BABAR data on the photon-pion transition form factor. Some aspects of the scenario with flat pion distribution amplitude are discussed.

We study LHC signatures of the type III seesaw mechanism in which $SU(2{)}_L$ triplet leptons are introduced to supply the heavy seesaw masses. To detect the signals of these heavy triplet leptons, one needs to understand their decays to standard model particles which depend on how light and heavy leptons mix with each other. We concentrate on the usual solutions with small light and heavy lepton mixing of the order of the square root of the ratio of light and heavy masses, $(m_{\nu }/M_{{\nu }_R}{)}^{1/2}$. This class of solutions can lead to a visible displaced vertex detectable at the LHC which can be used to distinguish small mixing and large mixing between light and heavy leptons. We show that, in this case, the couplings of light and heavy triplet leptons to gauge and Higgs bosons, which determine the decay widths and branching ratios, can be expressed in terms of light neutrino masses and their mixing. Using these relations, we study heavy triplet lepton decay patterns and production cross section at the LHC. If these heavy triplet leptons are below a TeV or so, they can be easily produced at the LHC due to their gauge interactions from being nontrivial representations of $SU(2{)}_L$. We consider two ideal production channels, (1) $E^{+}{E}^{-}\to {\ell }^{+}{\ell }^{+}{\ell }^{-}{\ell }^{-}jj$ ($\ell =e$, $\mu$, $\tau$) and (2) $E^{\pm }N\to {\ell }^{\pm }{\ell }^{\pm }jjjj$ in detail. For case 1, we find that with one or two of the light leptons being $\tau$ it can also be effectively studied. With judicious cuts at the LHC, the discovery of the heavy triplet leptons as high as a TeV can be achieved with $100{\mathrm{fb}}^{-1}$ integrated luminosity.

We derived equations of motion corresponding to Bianchi-I cosmological models in the Lovelock gravity. Equations derived in the general case, without any specific ansatz for any number of spatial dimensions and any order of the Lovelock correction. We also analyzed the equations of motion solely taking into account the highest-order correction and described the drastic difference between the cases with odd and even numbers of spatial dimensions. For power-law ansatz we derived conditions for Kasner and generalized Milne regimes for the model considered. Finally, we discuss the possible influence of matter in the form of perfect fluid on the solutions obtained.

Superfluids support many different types of sound waves. We investigate the relation between the sound waves in a relativistic and a nonrelativistic superfluid by using hydrodynamics to calculate the various sound speeds. Then, using a particular holographic scalar gravity realization of a strongly interacting superfluid, we compute first, second, and fourth sound speeds as a function of the temperature. The relativistic low temperature results for second sound differ from Landau’s well known prediction for the nonrelativistic, incompressible case.

We present an improved laboratory test of Lorentz invariance in electrodynamics by testing the isotropy of the speed of light. Our measurement compares the resonance frequencies of two orthogonal optical resonators that are implemented in a single block of fused silica and are rotated continuously on a precision air bearing turntable. An analysis of data recorded over the course of one year sets a limit on an anisotropy of the speed of light of $\Delta c/c\sim 1\times {10}^{-17}$. This constitutes the most accurate laboratory test of the isotropy of $c$ to date and allows to constrain parameters of a Lorentz violating extension of the standard model of particle physics down to a level of ${10}^{-17}$.

In this work we analyze complex scalar fields using a new framework where the object of noncommutativity ${\theta }^{\mu \nu }$ represents independent degrees of freedom. In a first quantized formalism, ${\theta }^{\mu \nu }$ and its canonical momentum ${\pi }_{\mu \nu }$ are seen as operators living in some Hilbert space. This structure is compatible with the minimal canonical extension of the Doplicher-Fredenhagen-Roberts algebra and is invariant under an extended Poincaré group of symmetry. In a second quantized formalism perspective, we present an explicit form for the extended Poincaré generators and the same algebra is generated via generalized Heisenberg relations. We also introduce a source term and construct the general solution for the complex scalar fields using the Green’s function technique.

We present a reanalysis of nonstandard neutrino-down-quark interactions of electron and tau neutrinos using solar, reactor, and accelerator data. In addition updating the analysis by including new solar data from SNO phase III and Borexino, as well as new KamLAND data and solar fluxes, a key role is played in our analysis by the combination of these results with the CHARM data. The latter allows us to better constrain the axial and axial-vector electron and tau-neutrino nonstandard interaction parameters characterizing the deviations from the standard model predictions.

The flat, homogeneous, and isotropic universe with a massless scalar field is a paradigmatic model in loop quantum cosmology. In spite of the prominent role that the model has played in the development of this branch of physics, there still remain some aspects of its quantization which deserve a more detailed discussion. These aspects include the kinematical resolution of the cosmological singularity, the precise relation between the solutions of the densitized and nondensitized versions of the quantum Hamiltonian constraint, the possibility of identifying superselection sectors which are as simple as possible, and a clear comprehension of the Wheeler-DeWitt (WDW) limit associated with the theory in those sectors. We propose an alternative operator to represent the Hamiltonian constraint which is specially suitable to deal with all these issues in a detailed and satisfactory way. In particular, with our constraint operator, the singularity decouples in the kinematical Hilbert space and can be removed already at this level. Thanks to this fact, we can densitize the quantum Hamiltonian constraint in a well-controlled manner. Additionally, together with the physical observables, this constraint superselects simple sectors for the universe volume, with a discrete support contained in a single semiaxis of the real line and for which the basic functions that encode the information about the geometry possess optimal physical properties. Namely, they provide a no-boundary description around the cosmological singularity and admit a well-defined WDW limit in terms of standing waves. Both properties explain the presence of a generic quantum bounce replacing the classical singularity at a fundamental level, in contrast with previous studies where the bounce was proved in concrete regimes—focusing on states with a marked semiclassical behavior—or for a simplified model.

This paper presents an algorithm for constructing matched-filter template banks in an arbitrary parameter space. The method places templates at random, then removes those which are “too close” together. The properties and optimality of stochastic template banks generated in this manner are investigated for some simple models. The effectiveness of these template banks for gravitational wave searches for binary inspiral waveforms is also examined. The properties of a stochastic template bank are then compared to the deterministically placed template banks that are currently used in gravitational wave data analysis.

We calculate and discuss the one-loop corrections to the photon sector of QED interacting to a background gravitational field. At high energies the fermion field can be taken as massless and the quantum terms can be obtained by integrating conformal anomaly. We present a covariant local expression for the corresponding effective action, similar to the one obtained earlier for the gravitational sector. At the moderate energies the quantum terms can be obtained through the heat-kernel method. In this way we derive the exact one-loop $\beta$ function for the electric charge in the momentum subtraction scheme and explore both massless and large-mass limits. The relation between the two approaches is shown and the difference discussed in view of the possible applications to cosmology and astrophysics.

Three-forms can give rise to viable cosmological scenarios of inflation and dark energy with potentially observable signatures distinct from standard single scalar field models. In this study, the background dynamics and linear perturbations of self-interacting three-form cosmology are investigated. The phase space of cosmological solutions possesses (super)-inflating attractors and saddle points, which can describe three-form driven inflation or dark energy. The quantum generation and the classical evolution of perturbations is considered. The scalar and tensor spectra from a three-form inflation and the impact from the presence of a three-form on matter perturbations are computed. Stability properties and equivalence of the model with alternative formulations are discussed.

Taking into account the $SU(3{)}_f$ breaking effects, the strong coupling constants of the $\pi$, $K$, and $\eta$ mesons with decuplet baryons are calculated within the light cone QCD sum rules method. It is shown that all coupling constants, even in the case of $SU(3{)}_f$ breaking, are described in terms of only one universal function. It is shown that for ${\Xi }^{*0}\to {\Xi }^{*0}\eta$, transition violation of $SU(3{)}_f$ symmetry is very large and for other channels when $SU(3{)}_f$ symmetry is violated, its maximum value constitutes $10\%÷15\%$.

The standard model predictions for the hadronic and leptonic electric dipole moments (EDMs) are considerably far from the present experimental resolutions; thus, the EDMs represent very clean probes of new physics effects. Especially, within supersymmetric frameworks with flavor-violating soft terms, large and potentially visible effects to the EDMs are typically expected. In this work, we systematically evaluate the predictions for the EDMs at the beyond leading order. In fact, we show that beyond-leading-order contributions to the EDMs dominate over the leading-order effects in large regions of the supersymmetric parameter space. Hence, their inclusion in the evaluation of the EDMs is unavoidable. As an example, we show the relevance of beyond-leading-order effects to the EDMs for a supersymmetric $SU(5)$ model with right-handed neutrinos.

We perform a first global exploration of the constrained next-to-minimal supersymmetric standard model using Bayesian statistics. We derive several global features of the model and find that, in some contrast to initial expectations, they closely resemble those of the constrained minimal supersymmetric standard model. This remains true even away from the decoupling limit which is nevertheless strongly preferred. We present ensuing implications for several key observables, including collider signatures and predictions for direct detection of dark matter.

A supersymmetric $SO(10)\times A_4$ grand unified theory model is constructed for fermion masses and mixing by introducing a minimal set of low dimensional Higgs representations needed to break the gauge symmetry down to $SU(3{)}_c\times U(1{)}_{\mathrm{em}}$. The hierarchy of fermion masses can be understood in the framework of $A_4$ symmetry. From the $A_4$-invariant superpotential, the “double lopsided” mass matrices for the charged leptons and the down quarks are obtained. It is shown that this structure simultaneously leads to bi-large neutrino mixings and small Cabibbo-Kobayashi-Maskawa mixing angles. An excellent fit to the masses and mixings of the quarks and leptons as well as to the $CP$ violation parameter is obtained. Moreover, the model predicts the neutrino mixing angle $\sin {\theta }_{13}\approx 0.15$.

We study a new supersymmetric mechanism for lepton flavor violation in $\mu$ and $\tau$ decays and $\mu \to e$ conversion in nuclei, within a minimal extension of the minimal supersymmetric standard model with low-mass heavy singlet neutrinos and sneutrinos. We find that the decays $\mu \to e\gamma$, $\tau \to e\gamma$ and $\tau \to \mu \gamma$ are forbidden in the supersymmetric limit of the theory, whereas other processes, such as $\mu \to eee$, $\mu \to e$ conversion, $\tau \to eee$ and $\tau \to e\mu \mu$, are allowed and can be dramatically enhanced several orders of magnitude above the observable level by potentially large neutrino Yukawa coupling effects. The profound implications of supersymmetric lepton flavor violation for present and future experiments are discussed.

Higher derivative field theories with interactions raise serious doubts about their validity due to severe energy instabilities. In many cases the implementation of a direct perturbation treatment to excise the dangerous negative-energies from a higher derivative field theory may lead to violations of Lorentz and other symmetries. In this work we study a perturbative formulation for higher derivative field theories that allows the construction of a low-energy effective field theory being a genuine perturbations over the ordinary-derivative theory and having a positive-defined Hamiltonian. We show that some discrete symmetries are recovered in the low-energy effective theory when the perturbative method to reduce the negative-energy degrees of freedom from the higher derivative theory is applied. In particular, we focus on the higher derivative Maxwell-Chern-Simons model which is a Lorentz invariant and parity-odd theory in $2+1$ dimensions. The parity violation arises in the effective action of ${\mathrm{QED}}_3$ as a quantum correction from the massive fermionic sector. We obtain the effective field theory which remains Lorentz invariant, but parity invariant to the order considered in the perturbative expansion.

In this work, we construct traversable wormhole geometries in the context of $f(R)$ modified theories of gravity. We impose that the matter threading the wormhole satisfies the energy conditions, so that it is the effective stress-energy tensor containing higher order curvature derivatives that is responsible for the null energy condition violation. Thus, the higher order curvature terms, interpreted as a gravitational fluid, sustain these nonstandard wormhole geometries, fundamentally different from their counterparts in general relativity. In particular, by considering specific shape functions and several equations of state, exact solutions for $f(R)$ are found.