In an attempt to uncover any underlying physics in the standard model (SM), we suggest a $\mu –\tau$ power law in the lepton sector, such that relatively large 13 mixing angle with bilarge ones can be derived. On the basis of this, we propose a neat and economical model for both the fermion mass hierarchy problem of the SM and a solution to the strong charge parity ($CP$) problem, in a way that no domain wall problem occurs, based on $A_4\times U(1{)}_X$ symmetry in a supersymmetric framework. Here we refer to the global $U(1{)}_X$ symmetry that can explain the above problems as “flavored Peccei-Quinn symmetry.” In the model, a direct coupling of the SM gauge singlet flavon fields responsible for spontaneous symmetry breaking to ordinary quarks and leptons, both of which are charged under $U(1{)}_X$, comes to pass through Yukawa interactions, and all vacuum expectation values breaking the symmetries are connected to each other. So the scale of Peccei-Quinn symmetry breaking is shown to be roughly located around the $10^{12}\mathrm{GeV}$ section through its connection to the fermion masses. The model predictions are shown to lie on the testable regions in the very near future through on-going experiments for neutrino oscillation, neutrinoless double beta decay, and the axion. We examine the model predictions, arisen from the $\mu –\tau$ power law, on leptonic $CP$ violation, neutrinoless double beta decay, and atmospheric mixing angle, and show that the fermion mass and mixing hierarchies are in good agreement with the present data. Interestingly, we show the model predictions on the axion mass $m_a\simeq 2.53\times 10^{-5}\mathrm{eV}$ and the axion coupling to photon $g_{a\gamma \gamma }\simeq 1.33\times 10^{-15}{\mathrm{GeV}}^{-1}$. And subsequently the square of the ratio between them is shown to be one or two orders of magnitude lower than that of the conventional axion model.

Pure gravity mediation, with two free parameters, is a minimalistic approach to supergravity models, yet it is capable of incorporating radiative electroweak symmetry breaking, a Higgs mass in agreement with the experimental measurement, without violating any phenomenological constraints. The model may also contain a viable dark matter candidate in the form of a wino. Here, we extend the minimal model by allowing the $\mu$ term to be a free parameter equivalent to allowing the two Higgs soft masses, $m_1$ and $m_2$, to differ from other scalar masses, which are set by the gravitino mass. In particular, we examine the region of parameter space where $\mu \ll m_{3/2}$, in which case the Higgsino becomes the lightest supersymmetric particle and a dark matter candidate. We also consider a generalization of pure gravity mediation that incorporates a Peccei-Quinn symmetry which determines the $\mu$ term dynamically. In this case we show that the dark matter may either be in the form of an axion and/or a neutralino and that the lightest supersymmetric particle may be either a wino, bino, or Higgsino.

Theories of physics beyond the standard model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs boson to the top quark. With extensions of the standard model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the standard model particles. This results in corrections to the Higgs production and decay rates that can be detected at the LHC provided the top partners are sufficiently light, and the theory correspondingly natural. In this paper we consider three theories that address the little hierarchy problem and involve colorless top partners, specifically the mirror twin Higgs, folded supersymmetry, and the quirky little Higgs. For each model we investigate the current and future bounds on the top partners, and the corresponding limits on naturalness, that can be obtained from the Higgs program at the LHC. We conclude that the LHC will not be able to strongly disfavor naturalness, with mild tuning at the level of about one part in ten remaining allowed even with $3000{\mathrm{fb}}^{-1}$ of data at 14 TeV.

An extension of the Standard Model (SM) based on the non-Abelian discrete group $\mathrm{\Delta }(27)$ is considered. The $\mathrm{\Delta }(27)$ flavor symmetry is spontaneously broken only by gauge singlet scalar fields, therefore our model is free from any flavor changing neutral current (FCNC). We show that the model accounts simultaneously for the observed quark and lepton masses and their mixing. In the quark sector, we find that the up-quark mass matrix is flavor diagonal and the Cabbibo-Kobayashi-Maskawa (CKM) mixing matrix arises from down quarks. In the lepton sector, we show that the charged lepton mass matrix is almost diagonal. We also adopt type-I seesaw mechanism to generate neutrino masses. A deviated mixing matrix from tri-bimaximal Maki-Nakagawa-Sakata (MNS), with a correlation between $\sin {\theta }_{13}$ and ${\sin }^2{\theta }_{23}$ are illustrated.

Dijet events produced in LHC proton-proton collisions at a center-of-mass energy $\sqrt{s}=8\mathrm{TeV}$ are studied with the ATLAS detector using the full 2012 data set, with an integrated luminosity of $20.3{\mathrm{fb}}^{-1}$. Dijet masses up to about 4.5 TeV are probed. No resonancelike features are observed in the dijet mass spectrum. Limits on the cross section times acceptance are set at the 95% credibility level for various hypotheses of new phenomena in terms of mass or energy scale, as appropriate. This analysis excludes excited quarks with a mass below 4.06 TeV, color-octet scalars with a mass below 2.70 TeV, heavy $W^{\prime }$ bosons with a mass below 2.45 TeV, chiral $W^{*}$ bosons with a mass below 1.75 TeV, and quantum black holes with six extra space-time dimensions with threshold mass below 5.66 TeV.

We calculate the two-point Green’s functions of operators dual to fermions of maximal gauged supergravity in four and five dimensions, in finite-temperature backgrounds with finite charge density. The numerical method used in these calculations is based on differential equations for bilinears of the supergravity fermions rather than the equations of motion for the fermions themselves. The backgrounds we study have vanishing entropy density in appropriate extremal limits. Holographic Fermi surfaces are observed when the scalar field participating in the dual field theory operator has an expectation value, which makes sense from the point of view that the quasiparticles near the Fermi surfaces observed carry nonsinglet gauge quantum numbers in the dual field theory.

We consider the semiclassical dynamics of a free massive scalar field in a homogeneous and isotropic cosmological spacetime. The scalar field is quantized using the polymer quantization method assuming that it is described by a Gaussian coherent state. For quadratic potentials, the semiclassical equations of motion yield a universe that has an early “polymer inflation” phase which is generic and almost exactly de Sitter, followed by an epoch of slow-roll inflation. We compute polymer corrections to the slow-roll formalism, and discuss the probability of inflation in this model using a physical Hamiltonian arising from time gauge fixing. We also show how in this model, it is possible to obtain a significant amount of slow-roll inflation from sub-Planckian initial data, hence circumventing some of the criticisms of standard scenarios. These results show the extent to which a quantum gravity motivated quantization method affects early universe dynamics.

Based on a recent proposal for the gravitational entropy of free gravitational fields, we investigate the thermodynamic properties of black hole formation through gravitational collapse in the framework of the semitetrad $1+1+2$ covariant formalism. In the simplest case of an Oppenheimer–Snyder–Datt collapse, we prove that the change in gravitational entropy outside a collapsing body is related to the variation of the surface area of the body itself, even before the formation of horizons. As a result, we are able to relate the Bekenstein–Hawking entropy of the black hole end state to the variation of the vacuum gravitational entropy outside the collapsing body.

We study the bispectrum of the primordial curvature perturbation on uniform density hypersurfaces generated by a kind of the noncanonical warm inflation, wherein the inflation is provided by a noncanonical scalar inflaton field that is coupled to radiation through a thermal dissipation effect. We obtain an analytic form for the nonlinear parameter $f_{\mathrm{NL}}$ that describes the non-Gaussianity in first-order cosmological perturbation theory and analyze the magnitude of this nonlinear parameter. We make a comparison between our result and those of the standard inflation and the canonical warm inflation. We also discuss when the contribution to the non-Gaussianity due to the second-order perturbation theory becomes more important and what the observations predict. We take the Dirac-Born-Infeld inflation as a concrete example to find how the sound speed and the thermal dissipation strength to decide the non-Gaussianity and get a lower bound of the sound speed constrained by Planck.

In this paper we proposed a solution to the long-standing problem of the color glass condensate(CGC)/saturation approach: the powerlike fall of the scattering amplitudes at large $b$. This decrease leads to the violation of the Froissart theorem and makes the approach theoretically inconsistent. We showed in the paper that the sum of the pion loops results in the exponential fall of the scattering amplitude at large impact parameters and in the restoration of the Froissart theorem.

The dependence of the QCD coupling constant with a strong magnetic field and the implications for the critical temperature of the chiral phase transition are investigated. It is found that the coupling constant becomes anisotropic in a strong magnetic field and that the quarks, confined by the field to the lowest Landau level where they pair with antiquarks, produce an antiscreening effect. These results lead to inverse magnetic catalysis, providing a natural explanation for the behavior of the critical temperature in the strong-field region.

Within the Standard Model, starting with the most general mass matrices, we have used the facility of making weak basis transformations and have imposed the condition of “naturalness” to carry out their analysis within the texture-zero approach. Interestingly, our analysis reveals that a particular set of texture-4 zero quark mass matrices can be considered to be a unique viable option for the description of quark mixing data.

Simultaneous measurements of the $t\overline{t}$, $W^{+}{W}^{-}$, and $Z/{\gamma }^{*}\to \tau \tau$ production cross-sections using an integrated luminosity of $4.6{\mathrm{fb}}^{-1}$ of $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ collected by the ATLAS detector at the LHC are presented. Events are selected with two high transverse momentum leptons consisting of an oppositely charged electron and muon pair. The three processes are separated using the distributions of the missing transverse momentum of events with zero and greater than zero jet multiplicities. Measurements of the fiducial cross-section are presented along with results that quantify for the first time the underlying correlations in the predicted and measured cross-sections due to proton parton distribution functions. These results indicate that the correlated next-to-leading-order predictions for $t\overline{t}$ and $Z/{\gamma }^{*}\to \tau \tau$ underestimate the data, while those at next-to-next-to-leading-order generally describe the data well. The full cross-sections are measured to be $\sigma (t\overline{t})=181.2\pm 2.8_{-9.5}^{+9.7}\pm 3.3\pm 3.3\mathrm{pb}$, $\sigma (W^{+}{W}^{-})=53.3\pm 2.7_{-8.0}^{+7.3}\pm 1.0\pm 0.5\mathrm{pb}$, and $\sigma (Z/{\gamma }^{*}\to \tau \tau )=1174\pm 24_{-87}^{+72}\pm 21\pm 9\mathrm{pb}$, where the cited uncertainties are due to statistics, systematic effects, luminosity and the LHC beam energy measurement, respectively. The $W^{+}{W}^{-}$ measurement includes the small contribution from Higgs boson decays, $H\to W^{+}{W}^{-}$.

We consider $R^p$ inflation with $p\approx 2$, allowing small deviation from $R^2$ inflation. Using the inflaton potential in the Einstein frame, we construct a consistency relation between the scalar spectral index, the tensor-to-scalar ratio, as well as the running of the scalar spectral index, which will be useful to constrain a deviation from $R^2$ inflation in future observations.

In this work, we show that duality symmetry can be implemented for massive theories at the level of the action, whenever we can formulate appropriate gauge invariant actions. For a massive vectorial field, we use a known gauge invariant description, while for a massive graviton, we introduce a novel gauge invariant action in order to show duality invariance.

The new form of the $C$ metric proposed by Hong and Teo, in which the two structure functions are factorized, has proved useful in its analysis. In this paper, we extend this form to the case when a cosmological constant is present. The new form of this solution has two structure functions which are partially factorized; moreover, the roots of the structure functions are now regarded as fundamental parameters. This leads to a natural representation of the solution in terms of its so-called domain structure, in which the allowed coordinate range can be visualized as a “box” in a two-dimensional plot. The solution is then completely parametrized by the locations of the edges of this box, at least in the uncharged case. We also briefly analyze other possible domain structures—in the shape of a triangle and trapezoid—that might describe physically interesting space-times within the anti–de Sitter $C$ metric.

To reconcile the BICEP2 measurement on the tensor-to-scalar ratio $r$ with Planck constraint, a large negative running of scalar spectral index $n_s$ is needed. So the inflationary observable such as $n_s$ should be expanded at least to the second-order slow-roll parameters for single-field inflationary models. The large value of $r$ and the Lyth bound indicate that it is impossible to obtain the sub-Planckian excursion for the inflaton. However, we derive an absolutely minimal bound $\mathrm{\Delta }\varphi /M_{\text{Pl}}>\sqrt{r/2}$ on the inflaton excursion for single-field inflationary models, which can be applied to non-slow-roll inflationary models as well. This bound excludes the possibility of the small-field inflation with $\mathrm{\Delta }\varphi <0.1M_{\text{Pl}}$ if the BICEP2 result on $r$ stands, and it opens the window of sub-Planckian excursion with $\mathrm{\Delta }\varphi <M_{\text{Pl}}$ even if $r$ is as large as 0.1. To get the sub-Planckian excursion with $\mathrm{\Delta }\varphi <0.1M_{\text{Pl}}$, our modified bound requires $r<0.02$. Using a fifth-order polynomial potential as an explicit example, we show that it not only agrees with the observational results, but also violates the Lyth bound.

The Alpha Magnetic Spectrometer (AMS-02) has just published the unprecedentedly precise measurement of the cosmic electron and positron spectra. In this paper, we try to give a quantitative study on the AMS-02 results by a global fitting to the electron and positron spectra, together with the updated positron fraction data. The Markov chain Monte Carlo algorithm is adopted to do the fitting. The primary electron spectrum and the parameters for pulsars or dark matter that contribute extra positrons are determined simultaneously. We find that there is a hardening of the primary electron spectrum at $\sim 60\mathrm{GeV}$. With such a new feature at the background spectrum, both the pulsars and dark matter can explain the AMS-02 results very well. The dark matter scenario shows a drop at the positron fraction at $\sim 300\mathrm{GeV}$ but suffers very strong constraints from Fermi $\gamma$-ray observations. The fitting results also suggest that the propagation model with convection may be more favored by the lepton data than the reacceleration model.

Measurement of cosmic microwave background (CMB) temperature by Planck has resulted in extremely tight constraints on the $\mathrm{\Lambda }\mathrm{CDM}$ model. However the data indicate evidence of dipole modulated temperature fluctuations at large angular scale which is beyond the standard statistically isotropic (SI) $\mathrm{\Lambda }\mathrm{CDM}$ model. The signal measured by Planck requires a scale dependent modulation amplitude that is beyond the scope of the phenomenological model considered by Planck. We propose a phenomenological model with mixed modulation field for scalar and tensor perturbations which affect the temperature fluctuations at large angular scales. Hence this model is a possible route to explain the scale dependent nature of the modulation field. The salient prediction of this model is the direction dependent tensor to scalar ratio which results in an anisotropic stochastic gravitational wave background (SGWB). This feature is potentially measurable from the $B$-mode polarization map of Planck and BICEP-2 and leads to determination of the modulation strength. Measurability of SI violated polarization field due to this model is estimated for Planck and PRISM. Absence of the signal in the polarization field can restrict the viability of the model.