We investigate the potential for measuring the relative couplings of a low-mass Higgs boson at the Large Hadron Collider using $WH$, $ZH$, and $t\overline{t}H$ production, where the Higgs boson decays to tau-lepton pairs. With $100{\mathrm{fb}}^{-1}$ of $\sqrt{s}=14\mathrm{TeV}$ $pp$ collision data we find that these modes can improve sensitivity to coupling-ratio measurements of a Higgs boson with a mass of about $125\mathrm{GeV}/c^2$.

Loop quantum cosmology yields two kinds of quantum corrections to the effective equations of motion for cosmological perturbations. Here we focus on the holonomy kind and we study the problem of the closure of the resulting algebra of constraints when a scalar field is considered in the matter Hamiltonian. Up to now, tensor, vector and scalar perturbations were studied independently, leading to different algebras of constraints. The structures of the related algebras were imposed by the requirement of anomaly freedom. In this article we show that the algebra can be modified by a very simple quantum correction, holding for all types of perturbations. The Mukhanov-Sasaki equations of motion are similarly modified by a simple term.

We consider the expectation values of chiral primary operators in the presence of the interface in the 4-dimensional $\mathcal{N}=4$ super Yang-Mills theory. This interface is derived from D3-D5 system in type IIB string theory. These expectation values are computed classically in the gauge theory side. On the other hand, this interface is a holographic dual to type IIB string theory on ${\mathrm{AdS}}_5\times {\mathrm{S}}^5$ spacetime with a probe D5-brane. The expectation values are computed by the Gubser-Klebanov-Polyakov-Witten prescription in the gravity side. We find nontrivial agreement of these two results: the gauge theory side and the gravity side.

The origin of spectral singularities in finite-gap singly periodic $\mathcal{P}\mathcal{T}$-symmetric quantum systems is investigated. We show that they emerge from a limit of band-edge states in a doubly periodic finite gap system when the imaginary period tends to infinity. In this limit, the energy gaps are contracted and disappear, every pair of band states of the same periodicity at the edges of a gap coalesces and transforms into a singlet state in the continuum. As a result, these spectral singularities turn out to be analogous to those in the nonperiodic systems, where they appear as zero-width resonances. Under the change of topology from a noncompact into a compact one, spectral singularities in the class of periodic systems we study are transformed into exceptional points. The specific degeneration related to the presence of finite number of spectral singularities and exceptional points is shown to be coherently reflected by a hidden, bosonized nonlinear supersymmetry.

We present an exact plane wave solution of the most general shift-symmetric Horndeski (generalized Galileon) theory. The solution consists of the scalar part and the gravitational part with two polarization modes. The former is due to the presence of the nontrivial Galileon scalar field, and it is parametrized by an arbitrary function of the light-cone coordinate. For a trivial scalar field configuration, the solution is equivalent to the plane gravitational wave in general relativity. When the metric is Minkowski, we reproduce known results for the plane waves of $k$-essence and soliton-like solutions of a noncovariant Galileon model in a flat space-time.

Quantum corrections coming from massless fields conformally coupled with gravity are studied, in order to see if they can lead to avoidance of the annoying big rip singularity which shows up in a flat Friedmann-Robertson-Walker universe filled with dark energy and modeled by a scalar phantom field. The dynamics of the model are discussed for all values of the two parameters, named $\alpha >0$ and $\beta <0$, corresponding to the regularization process. The new results are compared with the ones obtained in [J. Haro J. Amoros, and E. Elizalde, Phys. Rev. D 83, 123528 (2011)] previously, where dark energy was modeled by means of a phantom fluid with equation of state $P=\omega \rho$, with $\omega <-1$.

We measure the cross-correlation of Atacama cosmology telescope cosmic microwave background (CMB) lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSS-XDQSO photometric catalog. The CMB lensing quasar cross-power spectrum is detected for the first time at a significance of $3.8\sigma$, which directly confirms that the quasar distribution traces the mass distribution at high redshifts $z>1$. Our detection passes a number of null tests and systematic checks. Using this cross-power spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and find the amplitude to be consistent with an earlier measurement from clustering; at redshift $z\approx 1.4$, the peak of the distribution of quasars in our maps, our measurement corresponds to a bias of $b=2.5\pm 0.6$. With the signal-to-noise ratio on CMB lensing measurements likely to improve by an order of magnitude over the next few years, our results demonstrate the potential of CMB lensing cross-correlations to probe astrophysics at high redshifts.

We evaluate two-body decay modes of neutralinos in the minimal supersymmetric Standard Model with complex parameters. Assuming heavy scalar quarks, we take into account all two-body decay channels involving charginos, neutralinos, (scalar) leptons, Higgs bosons and Standard Model gauge bosons. The evaluation of the decay widths is based on a full one-loop calculation including hard and soft QED radiation. Of particular phenomenological interest are decays involving the lightest supersymmetric particle (LSP), i.e., the lightest neutralino, or a neutral or charged Higgs boson. For the chargino/neutralino sector we employ two different renormalization schemes, which differ in the treatment of the complex phases. In the numerical analysis, we concentrate on the decay of the heaviest neutralino and show the results in the two different schemes. The higher-order corrections of the heaviest neutralino decay widths involving the LSP can easily reach a level of about 10–15%, while the corrections to the decays to Higgs bosons can be up to 20–30%, translating into corrections of similar size in the respective branching ratios. The difference between the two schemes, indicating the size of unknown two-loop corrections, is less than $\mathcal{O}(0.1\%)$. These corrections are important for the correct interpretation of LSP and Higgs production at the LHC and at a future linear $e^{+}{e}^{-}$ collider. The results will be implemented into the Fortran code FeynHiggs.

We test the possibility that the newly discovered 126 GeV boson is a pseudoscalar by examining the correlations among the loop-induced pseudoscalar decay branching fractions to $\gamma \gamma$, $Z{Z}^{*}$, $Z\gamma$, and $W{W}^{*}$ final states in a model-independent way. These four decays are controlled by only two effective operators, so that the rates in $Z\gamma$ and $W{W}^{*}$ are predicted now that the rates in $\gamma \gamma$ and $Z{Z}^{*}$, $Z{\gamma }^{*}\to 4\ell$ have been measured. We find that the pseudoscalar possibility is disfavored but not conclusively excluded. Experimental exclusion of the $Z\gamma$ decay to well below $\sigma /{\sigma }_{\mathrm{SM}}\sim 170$ or conclusive observation of the $W{W}^{*}$ decay near the Standard Model rate would eliminate the pseudoscalar possibility. The $Z\gamma$ exclusion should be possible using existing data. The only loophole in our argument is the possibility that the $4\ell$ signal comes from pseudoscalar decays to a pair of new neutral gauge bosons with mass near the $Z$ pole.

The effective interactions of dark matter with photons are fairly restricted. Yet both direct detection as well as monochromatic $\gamma$-ray signatures depend sensitively on the presence of such interactions. For a Dirac fermion, electromagnetic dipoles are possible but are very constrained. For Majorana fermions, no such terms are allowed. We consider signals of an effective theory with a Majorana dark matter particle and its couplings to photons. In the presence of a nearby excited state, there is the possibility of a magnetic dipole transition (magnetic inelastic dark matter), which yields both direct and indirect detection signals and, intriguingly, yields essentially the same size over a wide range of dipole strengths. Absent an excited state, the leading interaction of weakly interacting massive particles is similar to the Rayleigh scattering of low-energy photons from neutral atoms, which may be captured by an effective operator of dimension 7 of the form $\overline{\chi }\chi F_{\mu \nu }{F}^{\mu \nu }$. While it can be thought of as a phase of the magnetic inelastic dark matter scenario where the excited state is much heavier than the ground state, it can arise from other theories as well. We study the resulting phenomenology of this scenario: gamma-ray lines from the annihilation of weakly interacting massive particles; nuclear recoils in direct detection; and direct production of the weakly interacting massive particle pair in high-energy colliders. Considering recent evidence in particular for a 130 GeV line from the Galactic center, we discuss the detection prospects at upcoming experiments.

New data on the lepton mixing angle ${\theta }_{13}$ imply that the $e\mu$ element of the matrix $m_{\nu }{m}_{\nu }^{†}$, where $m_{\nu }$ is the neutrino Majorana mass matrix, cannot vanish. This implies a lower limit on lepton flavor violating processes in the $e\mu$ sector in a variety of frameworks, including Higgs triplet models or the concept of minimal flavor violation in the lepton sector. We illustrate this for the branching ratio of $\mu \to e\gamma$ in the type II seesaw mechanism, in which a Higgs triplet is responsible for neutrino mass and also mediates lepton flavor violation. We also discuss processes like $\mu \to e\overline{e}e$ and $\mu \to e$ conversion in nuclei. Since these processes have sensitivity on the individual entries of $m_{\nu }$, their rates can still be vanishingly small.

The semileptonic decay of single-top-quark production provides a strong probe for $W^{\prime }$ bosons at the CERN Large Hadron Collider. We propose an explicit search strategy for $pp\to W^{\prime }\to tb\to l\nu bj$ for use at 7 and 8 TeV collider energies and integrated luminosities ranging from 5 to $20{\mathrm{fb}}^{-1}$. Based on detector-simulated results, we predict that a lower bound can be placed on the mass of right-handed $W_R^{\prime }$ with standard model-like couplings of $m_{W_R^{\prime }}>1800\mathrm{GeV}$ at $\sqrt{S}=7\mathrm{TeV}$ with $5{\mathrm{fb}}^{-1}$ and of $m_{W_R^{\prime }}>2000\mathrm{GeV}$ at 8 TeV with $20{\mathrm{fb}}^{-1}$. For left-handed $W_L^{\prime }$ bosons, we find a lower bound of 1750–1800 GeV at 7 TeV and $5{\mathrm{fb}}^{-1}$, depending on the sign of the interference with standard model single-top-quark production. We present effective coupling $g^{\prime }$-dependent limits for accessible masses and stress the importance of these limits for comparison with theoretical models.

We study the effect of cooling on the spatial distribution of the topological charge density in quenched SU(2) lattice gauge theory with overlap fermions. We demonstrate that as the gauge field configurations are cooled, the Hausdorff dimension of regions where the topological charge is localized gradually changes from $d=2–3$ towards the total space dimension. Therefore, the cooling procedure destroys some of the essential properties of the topological charge distribution.

Dark matter stability can be achieved through a partial breaking of a flavor symmetry. In this framework we propose a type-II seesaw model where left-handed matter transforms nontrivially under the flavor group $\Delta (54)$, providing correlations between neutrino oscillation parameters, consistent with the recent Daya-Bay and RENO reactor angle measurements, as well as lower bounds for neutrinoless double beta decay. The dark matter phenomenology is provided by a Higgs-portal.

A generalized $CP$ symmetry for leptons is presented where $CP$ transformations are part of an $S_4$ symmetry that connects different families. We study its implications for lepton mixings in a gauge model realization of the idea using a type II seesaw for neutrino masses. The model predicts maximal atmospheric mixing, nonzero ${\theta }_{13}$ and maximal Dirac phase ${\delta }_D=\pm \frac{\pi }{2}$.

We investigate the real-time dynamics of the chiral magnetic effect in quantum electrodynamics and quantum chromodynamics. We consider a field configuration of parallel (chromo)electric and (chromo)magnetic fields with a weak perpendicular electromagnetic magnetic field. The chiral magnetic effect induces an electromagnetic current along this perpendicular magnetic field, which we will compute using linear response theory. We discuss specific results for a homogeneous sudden switch-on and a pulsed (chromo)electric field in a static and homogeneous (chromo)magnetic field. Our methodology can be easily extended to more general situations. The results are useful for investigating the chiral magnetic effect with heavy ion collisions and with lasers that create strong electromagnetic fields. As a side result we obtain the rate of chirality production for massive fermions in parallel electric and magnetic fields that are static and homogeneous.

We present a numerical study of the process of the kink-antikink collisions in the coupled one-dimensional two-component ${\varphi }^4$ model. Our results reveal two different soliton solutions which represent double kink configuration and a kink-nontopological soliton (lump) bound state. Collision of these solitons leads to reveal very rich structure which is related to the reversible energy exchange between the kinks, nontopological solitons and the internal vibrational modes. Various channels of the collisions are discussed; it is shown there is a new type of self-similar fractal structure which appears in the collisions of the relativistic kinks. There the width of the resonance windows increases with the increase of the impact velocity. An analytical approximation scheme is discussed in the limit of the perturbative coupling between the sectors. Considering the spectrum of linear fluctuations around the solitons we found that the double kink configuration is unstable if the coupling constant between the sectors is negative.

A key problem in making precise perturbative QCD predictions is the uncertainty in determining the renormalization scale $\mu$ of the running coupling ${\alpha }_s({\mu }^2)$. The purpose of the running coupling in any gauge theory is to sum all terms involving the $\beta$ function; in fact, when the renormalization scale is set properly, all nonconformal $\beta \ne 0$ terms in a perturbative expansion arising from renormalization are summed into the running coupling. The remaining terms in the perturbative series are then identical to that of a conformal theory; i.e., the corresponding theory with $\beta =0$. The resulting scale-fixed predictions using the principle of maximum conformality (PMC) are independent of the choice of renormalization scheme—a key requirement of renormalization group invariance. The results avoid renormalon resummation and agree with QED scale setting in the Abelian limit. The PMC is also the theoretical principle underlying the Brodsky-Lepage-Mackenzie procedure, commensurate scale relations between observables, and the scale-setting method used in lattice gauge theory. The number of active flavors $n_f$ in the QCD $\beta$ function is also correctly determined. We discuss several methods for determining the PMC scale for QCD processes. We show that a single global PMC scale, valid at leading order, can be derived from basic properties of the perturbative QCD cross section. The elimination of the renormalization scale ambiguity and the scheme dependence using the PMC will not only increase the precision of QCD tests, but it will also increase the sensitivity of collider experiments to new physics beyond the Standard Model.

Four-dimensional Lorentzian conformal field theory (CFT) is mapped onto 5D anti-de Sitter spacetime (AdS) from the viewpoint of “geometrizing” conformal current algebra. A large-$N$ expansion of the CFT is shown to lead to (infinitely many) weakly coupled AdS particles, in one-to-one correspondence with minimal color-singlet CFT primary operators. If all but a finite number of “protected” primary operators have very large scaling dimensions, it is shown that there exists a low AdS curvature effective field theory regime for the corresponding finite set of AdS particles. Effective 5D gauge theory and general relativity on AdS are derived in this way from the most robust examples of protected CFT primaries, Noether currents of global symmetries and the energy-momentum tensor. Witten’s prescription for computing CFT local-operator correlators within the AdS dual is derived. The main new contribution is the derivation of 5D locality of AdS couplings. This is accomplished by studying a confining IR deformation of the CFT in the large-$N$ “planar” approximation, where the discrete spectrum and existence of an $S$ matrix allow the constraints of unitarity and crossing symmetry to be solved (in standard fashion) by a tree-level expansion in terms of 4D local “glueball” couplings. When the deformation is carefully removed, this 4D locality (with plausible assumptions specifying its precise nature) combines with the restored conformal symmetry to yield 5D AdS locality. The sense in which AdS/CFT duality illustrates the possibility of emergent relativity and the special role of strong coupling are briefly discussed. Care is taken to conclude each step with well-defined mathematical expressions and convergent integrals.