Supersymmetric models with bilinear $R$-parity violation (BRpV) provide a framework for neutrino masses and mixing angles to explain neutrino oscillation data. We consider $CP$ violation within the new physical phases in BRpV and discuss their effect on the generation of neutrino masses and the decays of the lightest supersymmetric particle (LSP), being a light neutralino with mass $\sim 100\mathrm{GeV}$, at next-to-leading order. The decays affect the lepton and via sphaleron transitions the baryon asymmetry in the early universe. For a rather light LSP, asymmetries generated before the electroweak phase transition via e.g. the Affleck-Dine mechanism are reduced up to 2 orders of magnitude, but are still present. On the other hand, the decays of a light LSP themselves can account for the generation of a lepton and baryon asymmetry, the latter in accordance with the observation in our universe, since the smallness of the BRpV parameters allows for an out-of-equilibrium decay and sufficiently large $CP$ violation is possible consistent with experimental bounds from the nonobservation of electric dipole moments.

Nonuniversal gaugino mass models can naturally account for the dark matter relic density via the bulk annihilation process with relatively light bino LSP and right sleptons in the mass range of $\sim 100\mathrm{GeV}$, while accommodating the observed Higgs boson mass of $\sim 125\mathrm{GeV}$ with TeV scale squark/gluino masses. A class of these models can also account for the observed muon g-2 anomaly via SUSY loops with wino and left sleptons in the mass range of 400–700 GeV. These models can be tested at LHC via electroweak production of charged and neutral wino pair, leading to robust trilepton and same sign dilepton signals. We investigate these signals along with the standard model background for both 8 and 13 TeV LHC runs.

We explore the mono-$Z$ signature for dark matter searches at future high energy $e^{+}{e}^{-}$ colliders. In the context of effective field theory, we consider two kinds of contact operators describing dark matter interactions with electroweak gauge bosons and with electron/positron, respectively. For five benchmark models, we propose kinematic cuts to distinguish signals from backgrounds for both charged leptonic and hadronic decay modes of the $Z$ boson. We also present the experimental sensitivity to cutoff scales of effective operators and compare it with that of the Fermi-LAT indirect search and demonstrate the gains in significance for the several configurations of polarized beams.

We perform an analysis of the QCD lattice data on the baryon octet and decuplet masses based on the relativistic chiral Lagrangian. The baryon self-energies are computed in a finite volume at next-to-next-to-next-to-leading order (${\mathrm{N}}^3\mathrm{LO}$), where the dependence on the physical meson and baryon masses is kept. The number of free parameters is reduced significantly down to 12 by relying on large-$N_c$ sum rules. Altogether we describe accurately more than 220 data points from six different lattice groups, BMW, PACS-CS, HSC, LHPC, QCDSF-UKQCD and NPLQCD. Values for all counterterms relevant at ${\mathrm{N}}^3\mathrm{LO}$ are predicted. In particular we extract a pion-nucleon sigma term of ${39}_{-1}^{+2}\mathrm{MeV}$ and a strangeness sigma term of the nucleon of ${\sigma }_{sN}=84_{-4}^{+28}\mathrm{MeV}$. The flavor SU(3) chiral limit of the baryon octet and decuplet masses is determined with ($802\pm 4$) and $(1103\pm 6)\mathrm{MeV}$. Detailed predictions for the baryon masses as currently evaluated by the ETM lattice QCD group are made.

In the framework of the color flux-tube model with a four-body confinement potential, the lowest charged tetraquark states $[Qq][{\overline{Q}}^{\prime }{\overline{q}}^{\prime }](Q=c,b,q=u,d,s)$ are studied by using the variational method, the Gaussian expansion method. The results indicate that some compact resonance states with three-dimensional spatial structures can be formed. These states cannot decay into two color singlet mesons $Q{\overline{q}}^{\prime }$ and ${\overline{Q}}^{\prime }q$ through the breakdown and recombination of color flux tubes but into $Q{\overline{Q}}^{\prime }$ and $q{\overline{q}}^{\prime }$. The four-body confinement potential is a crucial dynamical mechanism for the formation of these compact resonance states. The decay process is similar to that of a compound nucleus but due to the multibody color confinement. The newly observed charged states $Z_c(3900)$ and $Z_c(4025)/Z_c(4020)$ can be interpreted as the $S$-wave tetraquark states $[cu][\overline{c}\overline{d}]$ with quantum numbers $I{J}^P=11^{+}$ and $12^{+}$, respectively.

Recent estimates for the electromagnetic fields produced in the early stages of noncentral ultrarelativistic heavy ion collisions indicate the presence of magnetic fields $B\sim \mathcal{O}(0.1-15m_{\pi }^2)$, where $m_{\pi }$ is the pion mass. It is then of special interest to study the effects of strong (Abelian) magnetic fields on the transport coefficients of strongly coupled non-Abelian plasmas, such as the quark-gluon plasma formed in heavy ion collisions. In this paper we study the anisotropy in the shear viscosity induced by an external magnetic field in a strongly coupled $\mathcal{N}=4$ super Yang-Mills (SYM) plasma. Due to the spatial anisotropy created by the magnetic field, the most general viscosity tensor of a magnetized plasma has five shear viscosity coefficients and two bulk viscosities. We use the holographic correspondence to evaluate two of the shear viscosities, ${\eta }_{\perp }\equiv {\eta }_{xyxy}$ (perpendicular to the magnetic field) and ${\eta }_{\parallel }\equiv {\eta }_{xzxz}={\eta }_{yzyz}$ (parallel to the field). When $B\ne 0$ the shear viscosity perpendicular to the field saturates the viscosity bound ${\eta }_{\perp }/s=1/(4\pi )$, while in the direction parallel to the field the bound is violated since ${\eta }_{\parallel }/s<1/(4\pi )$. However, the violation of the bound in the case of strongly coupled SYM is minimal even for the largest value of $B$ that can be reached in heavy ion collisions.

We consider collective oscillations of neutrinos, which are emergent nonlinear flavor evolution phenomena instigated by neutrino-neutrino interactions in astrophysical environments with sufficiently high neutrino densities. We investigate the symmetries of the problem in the full three-flavor mixing scheme and in the exact many-body formulation by including the effects of $CP$ violation and the neutrino magnetic moment. We show that, similar to the two-flavor scheme, several dynamical symmetries exist for three flavors in the single-angle approximation if the net electron background in the environment and the effects of the neutrino magnetic moment are negligible. Moreover, we show that these dynamical symmetries are present even when the $CP$ symmetry is violated in neutrino oscillations. We explicitly write down the constants of motion through which these dynamical symmetries manifest themselves in terms of the generators of the SU(3) flavor transformations. We also show that the effects due to the $CP$-violating Dirac phase factor out of the many-body evolution operator and evolve independently of nonlinear flavor transformations if neutrino electromagnetic interactions are ignored. In the presence of a strong magnetic field, $CP$-violating effects can still be considered independently provided that an effective definition for the neutrino magnetic moment is used.

The present accelerated expansion of the Universe has enriched the list of possible scenarios for its fate, singular or not. In this paper a unifying framework for analyzing such behaviors is proposed, based on generalized power and asymptotic expansions of the barotropic index $w$, or equivalently of the deceleration parameter $q$, in terms of the time coordinate. Besides well-known singular and nonsingular future behaviors, other types of strong singularities appear around the phantom divide in flat models, with features similar to those of big rip or big bang/crunch, which we have dubbed “grand rip” and “grand bang/crunch,” respectively, since energy density and pressure diverge faster than $t^{-2}$ in coordinate time. In addition to this, the scale factor does not admit convergent generalized power series around these singularities with a finite number of terms with negative powers.

The theoretical foundations of the phenomenon known as superradiance still continue to attract considerable attention. Despite many valiant attempts at pedagogically clear presentations, the effect nevertheless still continues to generate some significant confusion. Part of the confusion arises from the fact that superradiance in a quantum field theory context is not the same as superradiance (superfluorescence) in some condensed matter contexts; part of the confusion arises from traditional but sometimes awkward normalization conventions, and part is due to sometimes unnecessary confusion between fluxes and probabilities. We shall argue that the key point underlying the effect is flux conservation (and, in the presence of dissipation, a controlled amount of flux nonconservation), and that attempting to phrase things in terms of reflection and transmission probabilities only works in the absence of superradiance. To help clarify the situation we present a simple exactly solvable toy model exhibiting both superradiance and damping.

The stability of dark matter is normally achieved by imposing extra symmetries beyond those of the Standard Model of particle physics. In this paper we present a framework where the dark matter stability emerges as a consequence of the Standard Model symmetries. The dark matter particle is an antisymmetric tensor field (analogous to the one used for spin-1 mesons in QCD), singlet under the Standard Model gauge group. The Lagrangian possesses an accidental $Z_2$ symmetry which makes the dark matter stable on cosmological time scales. Interactions with the Standard Model fields proceed through the Higgs portal, which allows the observed dark matter abundance to be generated via thermal freeze-out. We also discuss the prospects for observing this dark matter particle in direct detection experiments.

The reconstruction of a (non)canonical scalar field Lagrangian from the dark energy equation of state (EOS) parameter is studied, where it is shown that any EOS parametrization can be well reconstructed in terms of scalar fields. Several examples of EOS parameters are studied and the particular scalar field Lagrangian is reconstructed. Then, we propose some new parametrizations that may present a (fast) transition to a phantom dark energy EOS (where $w_{\mathrm{DE}}<-1$), and the scalar field Lagrangian is also reconstructed numerically. Furthermore, the properties of these parametrizations of the dark energy EOS are studied by using supernovae Ia data (HST Cluster Supernova Survey) combined with standard ruler data sets [cosmic microwave background (CMB) and baryon acoustic oscillations (BAO)] and its comparison with the $\mathrm{\Lambda }\mathrm{CDM}$ model is analyzed. Then, the best fit of the models is obtained, which provides some information about whether a phantom transition may be supported by the observations. In this regard, the crossing of the phantom barrier is allowed statistically but the occurrence of a future singularity seems unlikely.

Using an algebraic condition of vanishing discriminant for multiple roots of fourth-degree polynomials, we derive an analytical expression of a shadow size as a function of a charge in the Reissner-Nordström (RN) metric [1,2]. We consider shadows for negative tidal charges and charges corresponding to naked singularities $q={\mathcal{Q}}^2/M^2>1$, where $\mathcal{Q}$ and $M$ are black hole charge and mass, respectively, with the derived expression. An introduction of a negative tidal charge $q$ can describe black hole solutions in theories with extra dimensions, so following the approach we consider an opportunity to extend the RN metric to negative ${\mathcal{Q}}^2$, while for the standard RN metric ${\mathcal{Q}}^2$ is always non-negative. We found that for $q>9/8$, black hole shadows disappear. Significant tidal charges $q=-6.4$ (suggested by Bin-Nun [3–5]) are not consistent with observations of a minimal spot size at the Galactic Center observed in mm-band; moreover, these observations demonstrate that a Reissner-Nordström black hole with a significant charge $q\approx 1$ provides a better fit of recent observational data for the black hole at the Galactic Center in comparison with the Schwarzschild black hole.

We revisit the model proposed earlier to account for the observed increase in the positron fraction in cosmic rays with increasing energy, in the light of new data from the Alpha Magnetic Spectrometer (AMS-02) experiment. The model accounts for the production and acceleration of secondary electrons and positrons in nearby supernova remnants which results in an additional, harder component that becomes dominant at high energies. By fitting this to AMS-02 data we can calculate the expected concomitant rise of the boron-to-carbon ratio, as well as of the fraction of antiprotons. If these predictions are confirmed by the forthcoming AMS-02 data it would conclusively rule out all other proposed explanations, in particular, dark matter annihilations or decays.

In the spirit of the top-quark condensation, we propose a model which has a naturally light composite Higgs boson, “tHiggs” ($h_t^0$), to be identified with the 126 GeV Higgs discovered at the LHC. The tHiggs, a bound state of the top quark and its flavor (vectorlike) partner, emerges as a pseudo-Nambu–Goldstone boson (NGB), “top-mode pseudo-Nambu-Goldstone boson,” together with the exact NGBs to be absorbed into the $W$ and $Z$ bosons as well as another (heavier) top-mode pseudo-Nambu-Goldstone bosons ($CP$-odd composite scalar, $A_t^0$). Those five composite (exact/pseudo-) NGBs are dynamically produced simultaneously by a single supercritical four-fermion interaction having $U(3)\times U(1)$ symmetry which includes the electroweak symmetry, where the vacuum is aligned by a small explicit breaking term so as to break the symmetry down to a subgroup, $U(2)\times U(1{)}^{\prime }$, in a way not to retain the electroweak symmetry, in sharp contrast to the little Higgs models. The explicit breaking term for the vacuum alignment gives rise to a mass of the tHiggs, which is protected by the symmetry and hence naturally controlled against radiative corrections. Realistic top-quark mass is easily realized similarly to the top-seesaw mechanism by introducing an extra (subcritical) four-fermion coupling which explicitly breaks the residual $U(2{)}^{\prime }\times U(1{)}^{\prime }$ symmetry with $U(2{)}^{\prime }$ being an extra symmetry besides the above $U(3{)}_L\times U(1)$. We present a phenomenological Lagrangian of the top-mode pseudo-Nambu-Goldstone bosons along with the Standard Model particles, which will be useful for the study of the collider phenomenology. The coupling property of the tHiggs is shown to be consistent with the currently available data reported from the LHC. Several phenomenological consequences and constraints from experiments are also addressed.

When fixing a covariant gauge, most popularly the Landau gauge, on the lattice, one encounters the Neuberger $0/0$ problem, which prevents one from formulating a Becchi–Rouet–Stora–Tyutin symmetry on the lattice. Following the interpretation of this problem in terms of Witten-type topological field theory and using the recently developed Morse theory for orbifolds, we propose a modification of the lattice Landau gauge via orbifolding of the gauge-fixing group manifold and show that this modification circumvents the orbit-dependence issue and hence can be a viable candidate for evading the Neuberger problem. Using algebraic geometry, we also show that though the previously proposed modification of the lattice Landau gauge via stereographic projection relies on delicate departure from the standard Morse theory due to the noncompactness of the underlying manifold, the corresponding gauge-fixing partition function turns out to be orbit independent for all the orbits except in a region of measure zero.

Jets at high energy colliders are complicated objects to identify. Even if jets are widely separated, there is no reason to define jets with the same size. A single reconstruction of each event can only extract a limited amount of information. While the Qjet algorithm gives multiple interpretations for each event using nondeterministic jet clustering, here we propose a simple, fast and powerful deterministic method to probe each event with multiple angular scales $R$’s in the jet definition. Though qualitatively a different approach, the information we get from reconstructions at different angular scales can be analyzed in the framework of multiple event interpretations. We show that the statistical power of an analysis can be dramatically increased. In particular, we can have a 46% improvement, as compared to 28% using Qjets, in the statistical significance of the Higgs search with a $Z$ boson ($ZH\to \nu \overline{\nu }b\overline{b}$) at the 8 TeV LHC. Our work implies that the wide angle radiation contains useful information, which is a key observation that is overlooked in both the conventional and the Qjet analyses.

We present measurements of Collins asymmetries in the inclusive process $e^{+}{e}^{-}\to \pi \pi X$, where $\pi$ stands for charged pions, at a center-of-mass energy of 10.6 GeV. We use a data sample of $468{\mathrm{fb}}^{-1}$ collected by the BABAR experiment at the PEP-II $B$ factory at SLAC, and consider pairs of charged pions produced in opposite hemispheres of hadronic events. We observe clear asymmetries in the distributions of the azimuthal angles in two distinct reference frames. We study the dependence of the asymmetry on several kinematic variables, finding that it increases with increasing pion momentum and momentum transverse to the analysis axis, and with increasing angle between the thrust and beam axis.

The angular dependence of the gravitational radiation emitted in compact binary mergers and gravitational collapse is usually separated using spin-weighted spherical harmonics ${{}_{s}Y}_{\ell m}$ of spin weight $s$, that reduce to the ordinary spherical harmonics $Y_{\ell m}$ when $s=0$. Teukolsky first showed that the perturbations of the Kerr black hole that may be produced as a result of these events are separable in terms of a different set of angular functions: the spin-weighted spheroidal harmonics ${{}_{s}S}_{\ell mn}$, where $n$ denotes the “overtone index” of the corresponding Kerr quasinormal mode frequency ${\omega }_{\ell mn}$. In this paper we compute the complex-valued scalar products of the ${{}_{s}S}_{\ell mn}$’s with the ${{}_{s}Y}_{\ell m}$’s (“spherical-spheroidal mixing coefficients”) and with themselves (“spheroidal-spheroidal mixing coefficients”) as functions of the dimensionless Kerr parameter $j$. Tables of these coefficients and analytical fits of their dependence on $j$ are available online for use in gravitational-wave source modeling and in other applications of black-hole perturbation theory.