In this paper we study a parametrized description of neutrino mixing from a phenomenological point of view. We concentrate on the parametrization in terms of higher order corrections to the leading order mixing matrix. A method to describe subleading contributions and their applications to tribimaximal mixing are discussed. We show that mixing matrices similar to tribimaximal-Cabibbo mixing can be obtained by straightforward choices of parameters. To achieve better agreement with the experimental data without increasing the number of free parameters, we impose a simple phenomenological relation from which a trimaximal-like mixing matrix, parametrized by $U_{e3}=\sin {\theta }_{13}{e}^{-i\phi }$, can be derived straightforwardly without imposing additional requirements. It can describe the current global fit to three-neutrino mixing with good accuracy. Its theoretical explanation and phenomenological applications are discussed briefly.

We present a measurement of the mass difference between top ($t$) and antitop ($\overline{t}$) quarks using $t\overline{t}$ candidate events reconstructed in the final state with one lepton and multiple jets. We use the full data set of Tevatron $\sqrt{s}=1.96\mathrm{TeV}$ proton-antiproton collisions recorded by the CDF II detector, corresponding to an integrated luminosity of $8.7{\mathrm{fb}}^{-1}$. We estimate event by event the mass difference to construct templates for top pair signal events and background events. The resulting mass difference distribution in data compared to signal and background templates using a likelihood fit yields $\Delta M_{\mathrm{top}}=M_t-M_{\overline{t}}=-1.95\pm 1.11(\mathrm{stat})\pm 0.59(\mathrm{syst})\mathrm{GeV}/c^2$ and is in agreement with the standard model prediction of no mass difference.

We report a search for $CP$ violation in the decay modes $D^{\pm }\to K_S^0{K}^{\pm }$, $D_s^{\pm }\to K_S^0{K}^{\pm }$, and $D_s^{\pm }\to K_S^0{\pi }^{\pm }$ using a data set corresponding to an integrated luminosity of $469{\mathrm{fb}}^{-1}$ collected with the BABAR detector at the PEP-II asymmetric energy $e^{+}{e}^{-}$ storage rings. The decay rate $CP$ asymmetries, $A_{CP}$, are determined to be $(+0.13\pm 0.36(\mathrm{stat})\pm 0.25(\mathrm{syst}))\%$, $(-0.05\pm 0.23(\mathrm{stat})\pm 0.24(\mathrm{syst}))\%$, and $(+0.6\pm 2.0(\mathrm{stat})\pm 0.3(\mathrm{syst}))\%$, respectively. These measurements are consistent with zero, and also with the Standard Model prediction [$(-0.332\pm 0.006)\%$ for the $D^{\pm }\to K_S^0{K}^{\pm }$ and $D_s^{\pm }\to K_S^0{K}^{\pm }$ modes, and $(+0.332\pm 0.006)\%$ for the $D_s^{\pm }\to K_S^0{\pi }^{\pm }$ mode]. They are the most precise determinations to date.

The conformal transformations corresponding to $N$-Galilean conformal symmetries, previously defined as canonical symmetry transformations on phase space, are constructed as point transformations in coordinate space.

We investigate the appearance of arbitrary, regularization-dependent parameters introduced by divergent integrals in two a priori finite but superficially divergent amplitudes: the Higgs decay into two photons and the two-photon scattering. We use a general parametrization of ultraviolet divergences which makes explicit such ambiguities. Thus we separate in a consistent way using implicit regularization the divergent, finite, and regularization-dependent parts of the amplitudes which in turn are written as surface terms. We find that, although finite, these amplitudes are ambiguous before the imposition of physical conditions, namely, momentum routing invariance in the loops of Feynman diagrams. In the examples we study, momentum routing invariance turns out to be equivalent to gauge invariance. We also discuss the results obtained by different regularizations and show how they can be reproduced within our framework allowing for a clear view on the origin of regularization ambiguities.

We formulate a model of $N_f=4$ flavors of relativistic fermion in $2+1d$ in the presence of a chemical potential $\mu$ coupled to two flavor doublets with opposite sign, akin to isospin chemical potential in QCD. This is argued to be an effective theory for low energy electronic excitations in bilayer graphene, in which an applied voltage between the layers ensures equal populations of particles on one layer and holes on the other. The model is then reformulated on a spacetime lattice using staggered fermions, and in the absence of a sign problem, simulated using an orthodox hybrid Monte Carlo algorithm. With the coupling strength chosen to be close to a quantum critical point believed to exist for $N_f<N_{fc}\approx 4.8$, a range of $\mu$ below saturation is found where both the carrier density and a particle-hole “excitonic” condensate scale anomalously with increasing $\mu$, much more rapidly that the corresponding quantities in free field theory, while the conventional chiral condensate is strongly suppressed. The corresponding ground state is speculated to be a strongly correlated degenerate fermion system, with a remnant Fermi surface distorted by a superfluid excitonic condensate. The model thus shows qualitatively different behavior to any model with $\mu \ne 0$ previously studied by lattice simulation.

We investigate the topologically new massive gravity in three dimensions. It turns out that a single massive mode is propagating in the flat spacetime, comparing to the conformal Chern-Simons gravity, which has no physically propagating degrees of freedom. Also we discuss the realization of the Bondi-Metzner-Sachs/Galilean conformal algebras correspondence.

We consider the linearized semiclassical Einstein equations for small deviations around de Sitter spacetime including the vacuum polarization effects of conformal fields. Employing the method of order reduction, we find the exact solutions for general metric perturbations (of scalar, vector and tensor type). Our exact (nonperturbative) solutions show clearly that in this case de Sitter is stable with respect to small metric deviations and a late-time attractor. Furthermore, they also reveal a breakdown of perturbative solutions for a sufficiently long evolution inside the horizon. Our results are valid for any conformal theory, even self-interacting ones with arbitrarily strong coupling.

We consider the perturbative treatment of the minimally coupled, massless, self-interacting scalar field in Euclidean de Sitter space. Generalizing work of Rajaraman, we obtain the dynamical mass of the scalar for nonvanishing Lagrangian masses and the first perturbative quantum correction in the massless case. We develop the rules of a systematic perturbative expansion, which treats the zero-mode nonperturbatively and goes in powers of $\sqrt{\lambda }$. The infrared divergences are self-regulated by the zero-mode dynamics. Thus, in Euclidean de Sitter space the interacting, massless scalar field is just as well defined as the massive field. We then show that its dynamical mass $m^2\propto \sqrt{\lambda }{H}^2$ can be recovered from the diagrammatic expansion of the self-energy and a consistent solution of the Schwinger-Dyson equation, but it requires the summation of a divergent series of loop diagrams of arbitrarily high order. Finally, we note that the value of the long-wavelength mode two-point function in Euclidean de Sitter space agrees at leading order with the stochastic treatment in Lorentzian de Sitter space, in any number of dimensions.

The problem of matching different regions of spacetime in order to construct inhomogeneous cosmological models is investigated in the context of Lagrangian theories of gravity constructed from general analytic functions $f(R)$, and from nonanalytic theories with $f(R)=R^n$. In all of the cases studied, we find that it is impossible to satisfy the required junction conditions without the large-scale behavior reducing to that expected from Einstein’s equations with a cosmological constant. For theories with analytic $f(R)$ this suggests that the usual treatment of weak-field systems as perturbations about Minkowski space may not be compatible with late-time acceleration driven by anything other than a constant term of the form $f(0)$, which acts like a cosmological constant. In the absence of Minkowski space as a suitable background for weak-field systems, one must then choose and justify some other solution to perform perturbative analyses around. For theories with $f(R)=R^n$ we find that no known spherically symmetric vacuum solutions can be matched to an expanding Friedmann-Lemaître-Robertson-Walker background. This includes the absence of any Einstein-Straus-like embeddings of the Schwarzschild exterior solution in Friedmann-Lemaître-Robertson-Walker spacetimes.

In some models dark energy is described by phantom scalar fields (scalar fields with the “wrong” sign of the kinetic term in the Lagrangian). In the current paper we study the effect of phantom scalar field and/or phantom electromagnetic field on gravitational lensing by black holes in the strong deflection regime. The black-hole solutions that we have studied have been obtained in the frame of the Einstein-(anti-)Maxwell-(anti)dilaton theory. The numerical analysis shows a considerable effect of the phantom scalar and electromagnetic fields on the angular position, brightness, and separation of the relativistic images.

Assuming that no other conventional new physics is found immediately at the LHC, we investigate how just the consistent solution of the scalar mass hierarchy problem points towards the minimal necessary field content. We show that to ameliorate the fine-tuning problem, one needs to introduce more scalar degrees of freedom. The simplest solution is one or more real singlets (with the possibility of combining two of them in a complex singlet), which may act as viable cold dark matter candidates, because the constraints on the scalar potential disfavor any mixing between the new scalar(s) with the SM doublet. Furthermore, the fine-tuning problem of the new scalars necessitates the introduction of vectorlike fermions. Thus, singlet scalar(s) and vector fermions are minimal enhancements over the Standard Model to alleviate the fine-tuning problem. We also show that the model predicts Landau poles for all the scalar couplings, whose positions depend only on the number of such singlets. Thus, introduction of some new physics at that scale becomes inevitable. We also discuss how the model confronts the LHC constraints and the latest XENON100 data.

In this paper, we constrain $CP$ violation in the Higgs sector using the measured signal strengths in the various Higgs search channels. To this end, we introduce a general parametrization for a resonance which is an admixture of a $CP$-even Higgs-like state and a $CP$-odd scalar. By performing a fit to the available data from the Tevatron and LHC experiments, one obtains constraints on the mixing angle and the couplings of the resonance to Standard Model fields. Depending on the couplings, sizable mixing angles are still compatible with the data, but small mixing is in general preferred by the fit. In particular, we find that a pure $CP$-odd state is disfavored by the current data at the $3\sigma$ level. Additionally, we consider a mixed fermiophobic resonance and a model with two degenerate mixed resonances and find that both scenarios can successfully fit the data within current errors. Finally, we estimate that the mixing angle can be constrained to $\alpha <1.1$ (0.7) in the full 8 TeV (14 TeV) run of the LHC.

We perform perturbative QCD factorization of infrared radiations associated with an energetic $b$ quark from a polarized top quark decay, taking the semileptonic channel as an example. The resultant formula is expressed as a convolution of an infrared-finite heavy-quark kernel with a $b$-quark jet function. Evaluating the heavy-quark kernel up to leading order in the coupling constant and adopting the jet function from QCD resummation, we predict the dependence of the spin analyzing power for a polarized top quark on the invariant mass of the $b$-quark jet. It is observed that the spin analyzing power could be enhanced by a factor 2 compared to the inclusive case with the jet mass being integrated over. It is worthwhile to test experimentally the enhancement of the spin analyzing power due to the inclusion of jet dynamics.

We explore right-handed sneutrino-antisneutrino mixing in a TeV-scale $B-L$ extension of the Minimal Supersymmetric Standard Model, where a type-I seesaw mechanism of light neutrino mass generation is naturally implemented. The constraints imposed on the mass splitting between a heavy right-handed sneutrino and the corresponding antisneutrino by the experimental limits set on the light neutrino masses are investigated. We also study direct pair production of such right-handed sneutrinos at the Large Hadron Collider and their decay modes, emphasizing that their decay into same-sign dilepton pairs is a salient feature for probing these particles at the CERN machine. Finally, the charge asymmetry present in such same-sign dilepton signals is also analyzed and confirms itself as a further useful handle to extract information about the oscillation dynamics.

We compute one- and two-loop quadratic divergent contributions to the bare Higgs mass in terms of the bare couplings in the Standard Model. We approximate the bare couplings, defined at the ultraviolet cutoff scale, by the $\overline{\mathrm{MS}}$ ones at the same scale, which are evaluated by the two-loop renormalization group equations for the Higgs mass around 126 GeV in the Standard Model. We obtain the cutoff scale dependence of the bare Higgs mass, and examine where it becomes zero. We find that when we take the current central value for the top quark pole mass, 173 GeV, the bare Higgs mass vanishes if the cutoff is about ${10}^{23}\mathrm{GeV}$. With a $1.3\sigma$ smaller mass, 170 GeV, the scale can be of the order of the Planck scale.

Prolate spin-weighted spheroidal harmonics play a key role in black-hole perturbation theory. In particular, the highly damped quasinormal resonances of rotating Kerr black holes are closely related to the asymptotic eigenvalues of these important functions. We here present a novel and compact derivation of the asymptotic eigenvalues of the prolate spin-weighted spheroidal harmonics. Our analysis is based on a simple trick which transforms the corresponding spin-weighted spheroidal angular equation into a Schrödinger-like wave equation which is amenable to a standard WKB analysis. Our analytical results for the prolate asymptotic spectrum agree with previous numerical computations of the eigenvalues which appear in the literature.

It is well known that little string theory (LST) black holes radiate a purely thermal spectrum of scalar particles. This theory lives in a Hagedorn phase with a fixed Hagedorn temperature that does not depend on its mass. Therefore, the theory keeps a thermal profile even taking into account self-gravitating effects and the backreaction of the metric. This has implications concerning the information loss paradox; one would not be able to recover any information from the LST black hole since the emission of scalar particles is totally uncorrelated. Several studies of the emission spectrum in LST concern scalar fields; it is our aim in this work to extend the study to the emission of fermions in order to verify that the most relevant conclusion for the scalar field remains valid for the fermion fields. Thus, we have calculated the emission probability, the flux, and also the greybody factor corresponding to a fermion field in LST background.