Gluodynamics and two-flavor QCD at nonzero temperature are studied with the so-called overimproved cooling technique under which caloron solutions may remain stable. We consider topological configurations either at the first occuring stable plateau of topological charge or at the first (anti-) self-dual plateau and find the corresponding topological susceptibility at various temperatures on both sides of the thermal transition or crossover. In pure gluodynamics the topological susceptibility drops sharply at the deconfinement temperature, while in full QCD it decreases smoothly at temperatures above the pseudocritical one. The results are close to those calculated by other methods. We interpret our findings in terms of the (in)stability of calorons with nontrivial holonomy and their dyon constituents against overimproved cooling.

Results are presented of a search for the production of new particles decaying to pairs of partons (quarks, antiquarks, or gluons), in the dijet mass spectrum in proton-proton collisions at $\sqrt{s}=8\mathrm{TeV}$. The data sample corresponds to an integrated luminosity of $4.0{\mathrm{fb}}^{-1}$, collected with the CMS detector at the LHC in 2012. No significant evidence for narrow resonance production is observed. Upper limits are set at the 95% confidence level on the production cross section of hypothetical new particles decaying to quark-quark, quark-gluon, or gluon-gluon final states. These limits are then translated into lower limits on the masses of new resonances in specific scenarios of physics beyond the standard model. The limits reach up to 4.8 TeV, depending on the model, and extend previous exclusions from similar searches performed at lower collision energies. For the first time mass limits are set for the Randall–Sundrum graviton model in the dijet channel.

We investigate the effect of a homogeneous magnetic field on the thermal deconfinement transition of QCD in the large $N_c$ limit. First we discuss how the critical temperature decreases due to the inclusion of $N_f\ll N_c$ flavors of massless quarks in comparison to the pure glue case. Then we study the equivalent correction in the presence of an external Abelian magnetic field. To leading order in $N_f/N_c$, the deconfinement critical temperature decreases with the magnetic field if the flavor contribution to the pressure behaves paramagnetically, with a sufficiently large magnetization as to overcome any possible magnetic effects in the string tension. Finally, we discuss the effects from a finite quark mass and its competition with magnetic effects.

Highly accurate results from frequency measurements on neutral hydrogen molecules ${\mathrm{H}}_2$, HD, and ${\mathrm{D}}_2$ as well as the ${\mathrm{HD}}^{+}$ ion can be interpreted in terms of constraints on possible fifth-force interactions. Where the hydrogen atom is a probe for yet unknown lepton-hadron interactions, and the helium atom is sensitive for lepton-lepton interactions, molecules open the domain to search for additional long-range hadron-hadron forces. First principles calculations in the framework of quantum electrodynamics have now advanced to the level that hydrogen molecules and hydrogen molecular ions have become calculable systems, making them a search ground for fifth forces. Following a phenomenological treatment of unknown hadron-hadron interactions written in terms of a Yukawa potential of the form $V_5(r)=\beta \exp (-r/\lambda )/r$, current precision measurements on hydrogenic molecules yield a constraint $\beta <1.4\times {10}^{-8}\mathrm{eV}·\AA$ for long-range hadron-hadron interactions at typical force ranges commensurate with separations of a chemical bond, i.e., $\lambda \approx 1\AA$ and beyond. This corresponds to a constraint of $\beta /\alpha <{10}^{-9}$, where $\alpha$ represents the strength of the electromagnetic interaction, i.e., the fine-structure constant.

We search for the lepton-flavor-violating decay of the $J/\psi$ into an electron and a muon using $(225.3\pm 2.8)\times {10}^{6}J/\psi$ events collected with the BESIII detector at the BEPCII. Four candidate events are found in the signal region, consistent with background expectations. An upper limit on the branching fraction of $\mathcal{B}(J/\psi \to e\mu )<1.6\times {10}^{-7}$ (90% C.L.) is obtained.

A search for resonant diboson production using a data sample corresponding to $4.7{\mathrm{fb}}^{-1}$ of integrated luminosity collected by the ATLAS experiment at the Large Hadron Collider in $pp$ collisions at $\sqrt{s}=7\mathrm{TeV}$ is presented. The search for a narrow resonance in the $WW$ or $WZ$ mass distribution is conducted in a final state with an electron or a muon, missing transverse momentum, and at least two jets. No significant excess is observed and limits are set using three benchmark models: $WW$ resonance masses below 940 and 710 GeV are excluded at 95% confidence level for spin-2 Randall–Sundrum and bulk Randall–Sundrum gravitons, respectively; $WZ$ resonance masses below 950 GeV are excluded at 95% confidence level for a spin-1 extended gauge model $W^{\prime }$ boson.

In this paper I describe a collective coordinate approach to the study of giant graviton states and their excitations in various field theories. The method simplifies considerably the understanding of the emergent gauge symmetry of these configurations, as well as the calculation of the spectrum of strings stretched between the giant gravitons. There is a limit where these results reproduce the one-loop dispersion relation for giant magnons. I also show that this method gives rise to a simple geometric interpretation of a Higgs mechanism for the emergent gauge symmetry which parallels the holographic dual realization of these states: the effective Higgs condensate is the geometric separation of D-branes in the collective coordinate geometry.

We study the cosmological perturbations of the recently proposed extension of nonlinear massive gravity with a scalar field. The added scalar field ensures a new symmetry on the field space of the theory. The theory has the property of having a flat de Sitter solution, in contrast to the standard de Rham, Gabadadze and Tolley massive gravity. The tensor part is the same as that of the standard de Rham, Gabadadze and Tolley and shows gravitational waves with a time -dependent mass that modifies the dispersion relation. We obtain the curvature perturbation of the model on superhorizon scales for a specific choice of $\omega =0$ and find that the theory does not allow a constant curvature perturbation on the superhorizon scales and we have always a growing mode. The consistency of equations restricts the parameter space of the theory.

Dark matter annihilation or deexcitation, decay of metastable species, or other new physics may inject energetic electrons and photons into the photon-baryon fluid during and after recombination. As such particles cool, they partition their energy into a large number of efficiently ionizing electrons and photons, which in turn modify the ionization history. Recent work has provided a simple method for constraining arbitrary energy-deposition histories using the cosmic microwave background (CMB); in this note, we present results describing the energy-deposition histories for photons and electrons as a function of initial energy and injection redshift. With these results, the CMB bounds on any process injecting some arbitrary spectrum of electrons, positrons and/or photons with arbitrary redshift dependence can be immediately computed.

Strong gravitational lensing of time variable sources such as quasars and supernovae creates observable time delays between the multiple images. Time delays can provide a powerful cosmographic probe through the “time-delay distance” involving the ratio of lens, source, and lens-source distances. However, light curves of lensed images have measurement gaps, noise, systematics such as microlensing from substructure along an image line of sight, and no a priori functional model, making robust time-delay estimation challenging. Using Gaussian process techniques, we demonstrate success in accurate blind reconstruction of time delays and reduction in uncertainties for real data.

By combining the recent data from AMS-02 with those from Fermi-LAT, we show the emergence of a charge asymmetry in the electron and positron cosmic-ray excesses, slightly favoring the electron component. Astrophysical and dark matter inspired models introduced to explain the observed excesses can be classified according to their prediction for the charge asymmetry and its energy dependence. Future data confirming the presence of a charge asymmetry would imply that an asymmetric production mechanism is at play.

We investigate the spectacular collider signatures of macroscopically displaced, neutral particles that decay to Higgs bosons and missing energy. We show that such long-lived particles arise naturally in a very minimal extension of the Standard Model with only two new fermions with electroweak interactions. The lifetime of the long-lived neutral particles can range from ${10}^{-2}\mathrm{mm}$ to ${10}^6\mathrm{mm}$. In some regions of the parameter space, the exotic signals would have already been selected by the ATLAS and CMS triggers in their 7 and 8 TeV runs, hence hiding in the existing data. We also discuss the possibility of explaining the mild anomalies observed in the diphoton Higgs channel and the $WW$ production at the LHC.

We take into account a generic form of a Dirac fermionic dark matter (DM), which communicates with the Standard Model quarks via a scalar mediator in a model-independent way. Four special interaction scenarios are investigated, where one is parity conserving and the other three are parity violating. Three of them result in the $v$ suppressed DM-nucleon cross sections, where $v\sim {10}^{-3}c$ is the velocity of the DM in the laboratory frame. We constrain the masses of the dark matter and mediator as well as the couplings from the thermal relic abundance and the recent results of the XENON100 direct detection and collider experiments involving the following two channels: (i) monojet plus large missing transverse energy and (ii) dijet. The current monojet constraint is not stronger than that from the requirement of the correct relic density and the null result by the XENON100 direct detection. We find that the dijet resonance measurements can exclude a large part of the parameter space $(m_{\chi },m_Y)$, where the couplings for the mediator coupled to the dark matter and to the quarks are small and have roughly the same magnitude. The constraint from indirect detections and diphoton resonance searches is also briefly discussed.

We calculate differential distributions for the $pp\to pp\gamma$ reaction at the LHC energy $\sqrt{s}=14\mathrm{TeV}$. We consider diffractive classical bremsstrahlung mechanisms including effects of the non-point-like nature of protons. In addition, we take into account (vector meson)-pomeron, photon-pion, and photon-pomeron exchange processes for the first time in the literature. Predictions for the total cross section and several observables related to these processes, e.g., differential distributions in pseudorapidities and transverse momenta of photons or protons are shown and discussed. The integrated diffractive bremsstrahlung cross section ($E_{\gamma }>100\mathrm{GeV}$) is only of the order of $\mu \mathrm{b}$. We try to identify regions of the phase space where one of the mechanisms dominates. The classical bremsstrahlung dominates at large forward/backward photon pseudorapidities, close to the pseudorapidities of scattered protons. In contrast, the photon-pomeron (pomeron-photon) mechanism dominates at midrapidities but the related cross section is rather small. In comparison the virtual-omega–rescattering mechanism contributes at smaller angles of photons (larger photon rapidities). Photons in the forward/backward region can be measured by the Zero Degree Calorimeters installed in experiments at the LHC while the midrapidity photons are difficult to measure (small cross section, small photon transverse momenta). Protons could be measured by the ALFA detector (ATLAS) or TOTEM detector at CMS. The exclusivity could be checked with the help of main central detectors.

The dominant contribution to $H^{-}t\overline{b}$ production at the LHC is the gluon-gluon fusion parton subprocess. We perform for the case of the complex minimal supersymmetric standard model a complete calculation of the next-to-leading order (NLO) electroweak contributions to this channel. The other small contributions with quarks or photon in the initial state are calculated at tree level. The results are improved by using the effective bottom-Higgs couplings to resum the leading radiative corrections. We find that, beyond these leading corrections, the NLO electroweak contributions can still be significant. The effect of the complex phases of the soft-breaking parameters is found to be sizable.

We show that strongly coupled holographic matter at finite charge density can exhibit charge density wave phases which spontaneously break translation invariance while preserving time-reversal and parity invariance. We show that such phases are possible within Einstein-Maxwell-dilaton theory in general spacetime dimensions. We also discuss related spatially modulated phases when there is an additional coupling to a second vector field, possibly with nonzero mass. We discuss how these constructions, and others, should be associated with novel spatially modulated ground states.

We demonstrate that the warped ${\mathrm{AdS}}_3$ black hole solutions of topologically massive gravity are classically stable against massive scalar field perturbations by analyzing the quasinormal and bound state modes of the scalar field. In particular, it is found that although classical superradiance is present it does not give rise to superradiant instabilities. The stability is shown to persist even when the black hole is enclosed by a stationary mirror with Dirichlet boundary conditions. This is a surprising result in view of the similarity between the causal structure of the warped ${\mathrm{AdS}}_3$ black hole and the Kerr spacetime in $3+1$ dimensions. This work provides the foundations for the study of quantum field theory in this spacetime.

Measurement of pulsar timing residuals provides a direct way to detect relic gravitational waves at the frequency $f\sim 1/\mathrm{yr}$. In this paper, we investigate the constraints on the inflationary parameters, the tensor-to-scalar ratio $r$, and the tensor spectral index $n_t$, by the current and future pulsar timing arrays. We find that the Five-hundred-meter Aperture Spherical Radio Telescope in China and the planned Square Kilometre Array projects have fairly strong abilities to test the phantomlike inflationary models. If $r=0.1$, then Five-hundred-meter Aperture Spherical Radio Telescope could give the constraint on the spectral index $n_t<0.56$ and Square Kilometre Array could give $n_t<0.32$, while an observation with total time $T=20\mathrm{yr}$, pulsar noise level ${\sigma }_w=30\mathrm{ns}$, and monitored pulsar number $n=200$ could even constrain $n_t<0.07$. These are much tighter than those inferred from the current results of the Parkes Pulsar Timing Array, European Pulsar Timing Array, and North American Nanohertz Observatory for Gravitational Waves. By studying the effects of various observational factors on the sensitivities of pulsar timing arrays, we find that compared with ${\sigma }_w$ and $n$, the total observation time $T$ has the most significant effect.

On cosmological scales, observations of the cluster abundance currently place the strongest constraints on $f(R)$ gravity. These constraints lie in the large-field limit, where the modifications of general relativity can correctly be modeled by setting the Compton wavelength of the scalar field to its background value. These bounds are, however, at the verge of penetrating into a regime where the modifications become nonlinearly suppressed due to the chameleon mechanism and cannot be described by this linearized approximation. For future constraints based on observations subjected to cluster abundance, it is therefore essential to consistently model the chameleon effect. We analyze descriptions of the halo mass function in chameleon $f(R)$ gravity using a mass- and environment-dependent spherical collapse model in combination with excursion set theory and phenomenological fits to $N$-body simulations in the $\Lambda \mathrm{CDM}$ and $f(R)$ gravity scenarios. Our halo mass functions consistently incorporate the chameleon suppression and cosmological parameter dependencies, improving upon previous formalisms and providing an important extension to $N$-body simulations for the application in consistent tests of gravity with observables sensitive to the abundance of clusters.

The response of liquid xenon to low-energy electronic recoils is relevant in the search for dark-matter candidates which interact predominantly with atomic electrons in the medium, such as axions or axionlike particles, as opposed to weakly interacting massive particles which are predicted to scatter with atomic nuclei. Recently, liquid-xenon scintillation light has been observed from electronic recoils down to 2.1 keV, but without applied electric fields that are used in most xenon dark-matter searches. Applied electric fields can reduce the scintillation yield by hindering the electron-ion recombination process that produces most of the scintillation photons. We present new results of liquid xenon’s scintillation emission in response to electronic recoils as low as 1.5 keV, with and without an applied electric field. At zero field, a reduced scintillation output per unit deposited energy is observed below 10 keV, dropping to nearly 40% of its value at higher energies. With an applied electric field of $450\mathrm{V}/\mathrm{cm}$, we observe a reduction of the scintillation output to about 75% relative to the value at zero field. We see no significant energy dependence of this value between 1.5 and 7.8 keV. With these results, we estimate the electronic-recoil energy thresholds of ZEPLIN-III, XENON10, XENON100, and XMASS to be 2.8, 2.5, 2.3, and 1.1 keV, respectively, validating their excellent sensitivity to low-energy electronic recoils.