A definition of quantum singularity for the case of static spacetimes has recently been extended to conformally static spacetimes. Here the theory behind quantum singularities in conformally static spacetimes is reviewed and then applied to a class of spherically symmetric, conformally static spacetimes, including as special cases those studied by Roberts, by Fonarev, and by Husain et al. We use solutions of the generally coupled, massless Klein-Gordon equation as test fields. In this way we find the ranges of metric parameters and coupling coefficients for which classical timelike singularities in these spacetimes are healed quantum mechanically.

The origin of galactic and extragalactic magnetic fields is an unsolved problem in modern cosmology. A possible scenario comes from the idea that these fields emerged from a small field, a seed, which was produced in the early universe (phase transitions, inflation, etc.) and it evolves in time. Cosmological perturbation theory offers a natural way to study the evolution of primordial magnetic fields. The dynamics for this field in the cosmological context is described by a cosmic dynamolike equation, through the dynamo term. In this paper we get the perturbed Maxwell’s equations and compute the energy-momentum tensor to second order in perturbation theory in terms of gauge-invariant quantities. Two possible scenarios are discussed. First we consider a Friedmann-Lemaître-Robertson-Walker background without magnetic field, and we study the perturbation theory introducing the magnetic field as a perturbation. In the second scenario, we consider a magnetized Friedmann-Lemaître-Robertson-Walker and build up the perturbation theory from this background. We compare the cosmological dynamolike equation in both scenarios.

A violation of the reciprocity relation, which induces a violation of the distance-duality relation, reflects itself in a change in the normalization of the cosmic microwave spectrum in such a way that its spectrum is grey. We show that existing observational constraints imply that the reciprocity relation cannot be violated by more than 0.01% between decoupling and today. We compare this effect to other sources of violation of the distance-duality relations which induce spectral distortion of the cosmic microwave background spectrum.

Physical parameters are often constrained from the data likelihoods using sampling methods. Changing some parameters can be much more computationally expensive (“slow”) than changing other parameters (“fast parameters”). I describe a method for decorrelating fast and slow parameters so that parameter sampling in the full space becomes almost as efficient as sampling in the slow subspace when the covariance is well known and the distributions are simple. This gives a large reduction in computational cost when there are many fast parameters. The method can also be combined with a fast “dragging” method proposed by Neal arXiv:math/0502099 that can be more robust and efficient when parameters cannot be fully decorrelated a priori or have more complicated dependencies. I illustrate these methods for the case of cosmological parameter estimation, using data likelihoods from the Planck satellite observations with dozens of fast nuisance parameters, and demonstrate a speedup by a factor of five or more. In more complicated cases, especially where the fast subspace is very fast but complex or highly correlated, the fast-slow sampling methods can in principle give arbitrarily large performance gains. The new samplers are implemented in the latest version of the publicly available CosmoMC code.

The 1ES $1959+650$ is a high-peaked BL Lacertae object. On the 4th of June, 2002, it exhibited a strong TeV flare without any low energy counterpart, providing for the first time an example of an orphan flare from a blazar. Observation of this orphan flare is in striking disagreement with the predictions of the leptonic models thus challenging the conventional synchrotron self-Compton interpretation of the TeV emission. Here we propose that the low energy tail of the synchrotron self-Compton photons in the blazar jet serve as the target for the Fermi-accelerated high energy protons of energy $\lesssim 100\mathrm{TeV}$ within the jet to produce the TeV photons through the decay of neutral pions from the delta resonance. Our model explains very nicely the observed TeV flux from this orphan flare and we also estimate the high energy neutrino flux from this flaring event.

Temperature fluctuations are expected to be one of the limiting factors for gravitational-wave detectors in the very-low-frequency range. Here we report the characterization of this noise source in the LISA Pathfinder optical bench and propose a method to remove its contribution from the data. Our results show that temperature fluctuations are indeed limiting our measurement below one millihertz, and that their subtraction leads to a factor 5.6 (15 dB) reduction in the noise level at the lower end of the LISA measurement band (${10}^{-4}\mathrm{Hz}$), which increases to 20.2 (26 dB) at even lower frequencies, i.e., $1.5\times {10}^{-5}\mathrm{Hz}$. The method presented here can be applied to the subtraction of other noise sources in gravitational-wave detectors in the general situation where multiple sensors are used to characterize the noise source.

In the context of the gauge-Higgs unification scenario in a 5-dimensional flat spacetime, we investigate Higgs boson production via gluon fusion and its diphoton decay mode at the LHC. We show that the signal strength of the Higgs diphoton decay mode observed at ATLAS and CMS, which is considerably larger than the Standard Model expectation, can be explained by a simple gauge-Higgs unification model with color-singlet bulk fermions to which a half-periodic boundary condition is assigned. The bulk fermions also play a crucial role in reproducing the observed Higgs boson mass around 125 GeV.

In view of the recent measurement of the reactor mixing angle ${\theta }_{13}$ and updated limit on $\mathrm{BR}(\mu \to e\gamma )$ by the MEG experiment, we reexamine the charged lepton flavor violations in a framework of the supersymmetric type II seesaw mechanism. The supersymmetric type II seesaw predicts a strong correlation between $\mathrm{BR}(\mu \to e\gamma )$ and $\mathrm{BR}(\tau \to \mu \gamma )$ mainly in terms of the neutrino mixing angles. We show that such a correlation can be determined accurately after the measurement of ${\theta }_{13}$. We compute different factors that can affect this correlation and show that the minimal supergravity-like scenarios, in which slepton masses are taken to be universal at the high scale, predict $3.5\lesssim \mathrm{BR}(\tau \to \mu \gamma )/\mathrm{BR}(\mu \to e\gamma )\lesssim 30$ for normal hierarchical neutrino masses. Any experimental indication of deviation from this prediction would rule out the minimal models of the supersymmetric type II seesaw. We show that the current MEG limit puts severe constraints on the light sparticle spectrum in the minimal supergravity model if the seesaw scale lies within ${10}^{13}–{10}^{15}\mathrm{GeV}$. It is shown that these constraints can be relaxed and a relatively light sparticle spectrum can be obtained in a class of models in which the soft mass of a triplet scalar is taken to be nonuniversal at the high scale.

We explore the effects of neutrino and electron mixing with exotic heavy leptons in the process $e^{+}{e}^{-}\to W^{+}{W}^{-}$ within $E_6$ models. We examine the possibility of uniquely distinguishing and identifying such effects of heavy neutral lepton exchange from $Z\mathrm{\text{−}}{Z}^{\prime }$ mixing within the same class of models and also from analogous ones due to competitor models with anomalous trilinear gauge couplings that can lead to very similar experimental signatures at the $e^{+}{e}^{-}$ International Linear Collider for $\sqrt{s}=350$, 500 GeV and 1 TeV. Such clear identification of the model is possible by using a certain double polarization asymmetry. The availability of both beams being polarized plays a crucial role in identifying such exotic-lepton admixture. In addition, the sensitivity of the International Linear Collider for probing exotic-lepton admixture is substantially enhanced when the polarization of the produced $W^{\pm }$ bosons is considered.

A very light scalar top (stop) superpartner is motivated by naturalness and electroweak baryogenesis. When the mass of the stop is less than the sum of the masses of the top quark and the lightest neutralino superpartner ${\chi }_1^0$, as well as the of the masses of the lightest chargino and the bottom quark, the dominant decay channels of the stop will be three-body (3B: $b{W}^{+}{\chi }_1^0$), four-body (4B: $bf{\overline{f}}^{\prime }{\chi }_1^0$), or flavor violating (FV: $c{\chi }_1^0$). In this work, we investigate the direct and indirect constraints on a light stop, we compute the relative decay branching fractions to these channels, and we study the sensitivity of existing LHC searches to each of them.

We present a first $N_{\mathrm{f}}=2$ lattice estimate of the hadronic coupling $g_{12}$, which parametrizes the strong decay of a radially excited $B^{*}$ meson into the ground state $B$ meson at zero recoil. We work in the static limit of the heavy quark effective theory and solve a generalized eigenvalue problem, which is necessary for the extraction of excited state properties. After an extrapolation to the continuum limit and a check of the pion mass dependence, we obtain $g_{12}=-0.17(4)$.

We determine the infinite volume coefficients of the perturbative expansions of the self-energies of static sources in the fundamental and adjoint representations in SU(3) gluodynamics to order ${\alpha }^{20}$ in the strong coupling parameter $\alpha$. We use numerical stochastic perturbation theory, where we employ a new second order integrator and twisted boundary conditions. The expansions are obtained in lattice regularization with the Wilson action and two different discretizations of the covariant time derivative within the Polyakov loop. Overall, we obtain four different perturbative series. For all of them the high order coefficients display the factorial growth predicted by the conjectured renormalon picture, based on the operator product expansion. This enables us to determine the normalization constants of the leading infrared renormalons of heavy quark and heavy gluino pole masses and to translate these into the modified minimal subtraction scheme ($\overline{\mathrm{MS}}$). We also estimate the four-loop $\beta$-function coefficient of the lattice scheme.

We provide a status report on the advances in blocking-inspired supersymmetric actions. This is done with the example of interacting supersymmetric quantum mechanics as well as the Wess-Zumino model. We investigate in particular the implications of a nontrivial realization of translational symmetry on the lattice in this approach. We also discuss the locality of symmetry generators.

We present a determination, from lattice QCD, of charge symmetry violation in the spin-independent and spin-dependent parton distribution functions of the nucleon. This is done by chirally extrapolating recent QCDSF/UKQCD Collaboration lattice simulations of the first several Mellin moments of the parton distribution functions of octet baryons to the physical point. We find small chiral corrections for the polarized moments, while the corrections are quantitatively significant in the unpolarized case.

We discuss the uniqueness or nonuniqueness problem of the decomposition of the gluon field into the physical and pure-gauge components, which is the basis of the two recently proposed physically inequivalent gauge-invariant decompositions of the nucleon spin. It is crucially important to recognize the fact that the standard gauge-fixing procedure is essentially a process of projecting out the physical components of the massless gauge field. A complexity of the non-Abelian gauge theory as compared with the Abelian case is that a closed expression for the physical component can be given only with use of the nonlocal Wilson line, which is generally path dependent. It is known that—by choosing an infinitely long straight-line path in space and time, the direction of which is characterized by a constant four-vector $n^{\mu }$—one can cover a class of gauge called the general axial gauge, containing three popular gauges, i.e., the temporal, the light-cone, and the spatial axial gauge. Within this general axial gauge, we calculate the one-loop evolution matrix for the quark and gluon longitudinal spins in the nucleon. We find that the final answer is exactly the same independent of the choices of $n^{\mu }$, which amounts to proving the gauge independence and path independence simultaneously, although within a restricted class of gauges and paths. By drawing on all of these findings together with well-established knowledge from gauge theories, we argue against the rapidly spreading view in the community that there are infinitely many decompositions of the nucleon spin.

We perform a detailed comparison of long-range rapidity correlations in the color glass condensate framework to high multiplicity dihadron data in proton-proton and proton-lead collisions from the CMS, ALICE and ATLAS experiments at the LHC. The overall good agreement thus far of the nontrivial systematics of theory with data is strongly suggestive of gluon saturation and the presence of subtle quantum interference effects between rapidity separated gluons. In particular, the yield of pairs collimated in their relative azimuthal angle $\Delta \varphi \sim 0$, is sensitive to the shape of unintegrated gluon distributions in the hadrons that are renormalization group evolved in rapidity from the beam rapidities to those of the measured hadrons. We present estimates for the collimated dihadron yield expected in central deuteron-gold collisions at the Relativistic Heavy Ion Collider.

We consider the production of $B^{*}{\overline{B}}^{*}$ meson pairs in $e^{+}{e}^{-}$ annihilation near the threshold. The rescattering due to pion exchange between the mesons results in a mixing between three partial wave amplitudes: two $P$-wave amplitudes with the total spin of the meson pair $S=0$ and $S=2$ and an $F$-wave amplitude. The mixing due to pion exchange with a low momentum transfer is calculable up to c.m. energy $E\approx 15–20\mathrm{MeV}$ above the threshold. We find that the $P-F$ mixing is numerically quite small in this energy range, while the mixing of the two $P$-wave amplitudes is rapidly changing with energy and can reach of order one at such low energies.

We study the octet to decuplet baryon electromagnetic transitions using the covariant spectator quark model and predict the transition magnetic dipole form factors for those involving the strange baryons. Utilizing $SU(3)$ symmetry, the valence quark contributions are supplemented by the pion cloud dressing based on the one estimated in the ${\gamma }^{*}N\to \Delta$ reaction. Although the valence quark contributions are dominant in general, the pion cloud effects turn out to be very important to describe the experimental data. We also show that other mesons besides the pion, in particular the kaon, may be relevant for some reactions such as ${\gamma }^{*}{\Sigma }^{+}\to {\Sigma }^{*+}$, based on our analysis for the radiative decay widths of the strange decuplet baryons.

We investigate two exclusive processes, $e^{+}{e}^{-}\to {\eta }_c+\gamma$ and $e^{+}{e}^{-}\to J/\psi +J/\psi$, at the center-of-momentum energy $\sqrt{s}=10.58\mathrm{GeV}$ within the framework of the nonrelativistic QCD factorization approach. A class of relativistic corrections is resummed to all orders in the heavy-quark velocity $v$ and the corrections are large negative. We further improve the prediction by including available QCD next-to-leading-order corrections and the interference between the QCD and relativistic corrections. The prediction for $\sigma [e^{+}{e}^{-}\to {\eta }_c+\gamma ]$ is about 50 fb. In the case of $e^{+}{e}^{-}\to J/\psi +J/\psi$ the standard nonrelativistic QCD prediction for the cross section is negative. As an alternative, the vector-meson-dominance approach is employed to compute the photon-fragmentation contribution of the process, which gives the cross section $\sim 1\mathrm{fb}$. This is an indication that the uncalculated QCD higher-order corrections may be significant. Our results can be tested against the forthcoming data from Belle II and super $B$ factories.

Starting from the Seiberg-Witten solution of $\mathcal{N}=2$ supersymmetric QCD with the $\mathrm{U}(N)$ gauge group and $N_f$ quark flavors we construct the so-called $\mu$-dual $\mathcal{N}=1$ theory in the $r$ vacua in the regime analogous to that existing to the left of the left edge of the Seiberg conformal window, where $r$ is the number of condensed quarks. The strong-weak coupling duality is shown to exist in the so-called zero vacua which can be found at $r<N_f-N$. We show that the $\mu$-dual theory matches the Seiberg dual in the zero vacua.