Large Hadron Collider (LHC) searches for the SM Higgs boson provide a powerful limit on models involving universal extra dimensions (UED) where the Higgs production is enhanced. We have evaluated all one-loop diagrams for Higgs production $gg\to h$ and decay $h\to \gamma \gamma$ within “minimal” UED (mUED), independently confirming previous results, and we have evaluated enhancement factors for Higgs boson production and decay over the mUED parameter space. Using these we have derived limits on the parameter space, combining data from both ATLAS and CMS collaborations for the most recent 7 and 8 TeV LHC data. We have performed a rigorous statistical combination of several Higgs boson search channels which is important because mUED signatures from the Higgs boson are not universally enhanced. We have found that $R^{-1}<500\mathrm{GeV}$ is excluded at a 95% confidence level (CL), while for larger $R^{-1}$ only a very narrow ($\pm 1–4\mathrm{GeV}$) mass window around $m_h=125\mathrm{GeV}$ and another window (up to 2 GeV wide for $R^{-1}>1000\mathrm{GeV}$) around $m_h=118\mathrm{GeV}$ are left. The latter is likely to be excluded as more data becomes available whereas the region around $m_h=125\mathrm{GeV}$ is where the recently discovered Higgs-like particle was observed and therefore where the exclusion limit is weaker. It is worth stressing that mUED predicts an enhancement for all channels for $gg\to h$ production and decay while the vector boson fusion process $WW/ZZ\to h\to \gamma \gamma$ is generically suppressed and $WW/ZZ\to h\to W{W}^{*}/Z{Z}^{*}$ is standard. Therefore, as more 8 TeV LHC data becomes available, the information on individual Higgs boson production and decay processes provided by the CMS and ATLAS experiments can be effectively used to favor mUED or exclude it further.

Using Monte Carlo integration techniques, we investigate running coupling effects compatible with the high energy bootstrap condition to all orders in the strong coupling in evolution equations valid at small values of Bjorken $x$ in deep inelastic scattering. A model for the running of the coupling with analytic behavior in the infrared region and compatible with power corrections to jet observables is used. As a difference to the fixed coupling case, where the momentum transfer acts as an effective strong cutoff of the diffusion to infrared scales, in our running coupling study the dependence on the momentum transfer is much milder.

With a discrete $Z_2$ symmetry being imposed, we introduce a real singlet scalar $S$ to the Higgs triplet model with the motivation of explaining the tentative evidence for a line spectral feature at $E_{\gamma }=130\mathrm{GeV}$ in the Fermi Large Area Telescope data. The model can naturally satisfy the experimental constraints of the dark matter relic density and direct detection data from Xenon100. The doubly charged and single charged scalars can enhance the annihilation cross section of $SS\to \gamma \gamma$ via the one-loop contributions and give negligible contributions to the relic density. $⟨\sigma v{⟩}_{SS\to \gamma \gamma }$ for $m_S=130\mathrm{GeV}$ can reach $\mathcal{O}(1)\times {10}^{-27}{\mathrm{cm}}^3{\mathrm{s}}^{-1}$ for the small charged scalars’ masses and the coupling constant that is larger than 1. Also, this model predicts a second photon peak at 114 GeV from the annihilation $SS\to \gamma Z$, and the cross section is approximately 0.76 times that of $SS\to \gamma \gamma$, which is below the upper limit reported by Fermi Large Area Telescope. Finally, the light charged scalars can enhance the LHC diphoton Higgs rate and make it consistent with the experimental data reported by ATLAS and CMS.

Lüscher’s formula relates the elastic scattering phase shifts to the two-particle energy levels in a finite cubic box. The original formula was obtained for elastic scattering of two massive spinless particles in the center-of-mass frame. In this paper, we consider the case for the scattering of a spin $1/2$ particle with a spinless particle in a multichannel scattering. A generalized relation between the energy of the two-particle system and the scattering matrix elements is established. We first obtain this relation using quantum mechanics in both the center-of-mass frame and in a general moving frame. The result is then generalized to quantum field theory, using methods outlined by Hansen and Sharpe [Phys. Rev. D 86, 016007 (2012)]. We verify that the results obtained using both methods are equivalent up to terms that are exponentially suppressed in the box size.

We consider three-loop radiative-recoil corrections to hyperfine splitting in muonium generated by the gauge invariant set of diagrams with virtual light-by-light scattering block. These corrections are enhanced by the large logarithms of the electron-muon mass ratio. We present the results of an analytic calculation of the single-logarithmic radiative-recoil corrections of order ${\alpha }^2(Z\alpha )(m/M)E_F$ to hyperfine splitting in muonium generated by these diagrams.

The Bogomol’nyi-Prasad-Sommerfield (BPS) baby Skyrme models are submodels of baby Skyrme models, where the nonlinear sigma model term is suppressed. They have Skyrmion solutions saturating a BPS bound, and the corresponding static energy functional is invariant under area-preserving diffeomorphisms (APDs). Here we show that the solitons in the BPS baby Skyrme model, which carry a nontrivial topological charge $Q_b\in {\pi }_2(S^2)$ (a winding number), are dual to vortices in a BPS vortex model with a topological charge $Q_v\in {\pi }_1(S^1)$ (a vortex number), in the sense that there is a map between the BPS solutions of the two models. The corresponding energy densities of the BPS solutions of the two models are identical. A further consequence of the duality is that the dual BPS vortex models inherit the BPS property and the infinitely many symmetries (APDs) of the BPS baby Skyrme models. Finally, we demonstrate that the same topological duality continues to hold for the $U(1)$ gauged versions of the models.

In a series of papers, we examine the physical unitarity in a massive Yang-Mills theory without the Higgs field in which the color gauge symmetry is not spontaneously broken and kept intact. For this purpose, we use a new framework proposed in the previous paper Kondo [arXiv:1208.3521] based on a nonperturbative construction of a non-Abelian field describing a massive spin-one vector boson field, which enables us to perform the perturbative and nonperturbative studies on the physical unitarity. In this paper, we present a new perturbative treatment for the physical unitarity after giving the general properties of the massive Yang-Mills theory. Then we reproduce the violation of physical unitarity in a transparent way. This paper is a preliminary work to the subsequent papers in which we present a nonperturbative framework to propose a possible scenario of restoring the physical unitarity in the Curci-Ferrari model.

We present an exact solution in three-dimensional topologically massive gravity with a negative cosmological constant, which dynamically interpolates between a past horizon and a chiral anti–de Sitter $pp$ wave. Similarly, upon time reversal, one obtains an anti–de Sitter $pp$ wave with a future event horizon.

Collisions between cosmic bubbles of different vacua are a generic feature of false vacuum eternal inflation scenarios. While previous studies have focused on the consequences of a single collision event in an observer’s past, we begin here an investigation of the more general scenario allowing for many “mild” collisions intersecting our past light cone (and one another). We discuss the general features of multiple collision scenarios and consider their impact on the cosmic microwave background (CMB) temperature power spectrum, treating the collisions perturbatively. In a large class of models, one can approximate a multiple collision scenario as a superposition of individual collision events governed by nearly isotropic and scale-invariant distributions, most appearing to take up less than half of the sky. In this case, the shape of the expected CMB temperature spectrum maintains statistical isotropy and typically features a dramatic increase in power in the low multipoles relative to that of the best-fit $\Lambda \mathrm{CDM}$ model, which is in tension particularly with the observed quadrupole. We argue that this predicted spectrum is largely model independent and can be used to outline features of the underlying statistical distributions of colliding bubbles consistent with CMB temperature measurements.

We calculate technipion masses of the walking technicolor by explicitly evaluating nontrivial contributions from various possible chiral breaking sources in a concrete walking technicolor setting of the one-family model. Our explicit computation of the mass and the coupling in this concrete model setting reveals that the technipions are on the order of several hundred GeV in the region to be discovered at the LHC.

We discuss some possible signals of $CPT$ violation in the $B_s$ system that may be probed at the Large Hadron Collider. We show how one can construct combinations of observables coming from tagged and untagged decay rates of $B_s\to D_s^{\pm }{K}^{\mp }$ that can unambiguously differentiate between $CPT$ violating and $CPT$ conserving new physics models contributing in $B_s^0-{\overline{B}}_s^0$ mixing. We choose this particular mode as an illustrative example for two reasons: (i) In the Standard Model, there is only one decay amplitude, so it is easier to untangle any new physics; (ii) $B_s$ being a neutral meson, it is possible to unambiguously identify any sign of $CPT$ violation that occurs only in mixing but not in decay. We define an observable which is useful to extract the $CPT$ violating parameter in $B_s$ decay, and also discuss how far the results are applicable even if $CPT$ violation is present in both mixing and decay.

We introduce a nonperturbative continuum framework to study the dynamics of quantum field theory (QFT), applied here to the $CP(N-1)$ model. We show that the ambiguities in perturbation theory due to infrared renormalons are exactly canceled by corresponding ambiguities in the nonperturbative sector coming from amplitudes of certain nonperturbative objects: neutral bions and bion-antibions. This provides an explicit weak-coupling interpretation of the IR-renormalons. We use Écalle’s theory of resurgent trans-series and the physical principle of continuity to continuously connect QFT to quantum mechanics, while preventing all intervening rapid crossovers or phase transitions. The quantum mechanics contains the germ of all nonperturbative data, e.g., mass gap, of the QFT, all of which are calculable. For $CP(N-1)$, the results obtained at arbitrary $N$ are consistent with lattice and large-$N$ results. The trans-series expansion, in which perturbative and nonperturbative effects are intertwined, encapsulates the multilength-scale nature of the theory, and eliminates all perturbative and nonperturbative ambiguities under consistent analytic continuation of the coupling. A theorem by Pham et al. implies that the mass gap is a resurgent function, for which resummation of the semiclassical expansion yields finite exact results in the weakly coupled domain.

We show that the hidden conformal symmetry of the Schwarzschild black hole is realized from the ${\mathrm{AdS}}_2$ sector of the ${\mathrm{AdS}}_2\times S^2$ but not from the Rindler spacetime, which is the genuine near-horizon geometry of the Schwarzschild black hole. This implies that purely imaginary quasinormal frequencies obtained using the hidden conformal symmetry are not suitable for describing the largely damped modes around the Schwarzschild black hole.

We develop a general strategy to express noncommutative actions in terms of commutative ones by using a recently developed geometric generalization of the Seiberg-Witten map between noncommutative and commutative fields. We apply this general scheme to the noncommutative vierbein gravity action and provide a Seiberg-Witten differential equation for the action itself as well as a recursive solution at all orders in the noncommutativity parameter $\theta$. We thus express the action at order ${\theta }^{n+2}$ in terms of noncommutative fields of order at most ${\theta }^{n+1}$ and, iterating the procedure, in terms of noncommutative fields of order at most ${\theta }^n$. This in particular provides the explicit expression of the action at order ${\theta }^2$ in terms of the usual commutative spin connection and vierbein fields. The result is an extended gravity action on commutative spacetime that is manifestly invariant under local Lorentz rotations and general coordinate transformations.

We provide all basic equations and concepts required to carry out a general study on axially symmetric static sources. The Einstein equations and the conservation equations are written down for a general anisotropic static fluid endowed with axial symmetry. The structure scalars are calculated and the inhomogeneity factors are identified. Finally some exact analytical solutions were found. One of these solutions describes an incompressible spheroid with isotropic pressure and becomes the well-known interior Schwarzschild solution in the spherically symmetric limit; however, it cannot be matched smoothly to any Weyl exterior metric. Another family of solutions was found that corresponds to an anisotropic fluid distribution and can in principle be matched to a Weyl exterior.

We study the correlators for interacting quantum field theory in the flat chart of de Sitter space at all orders in perturbation. The correlators are calculated in the in-in formalism which is often applied to the calculations in the cosmological perturbation. It is shown that these correlators are de Sitter invariant. They are compared with the correlators calculated based on the Euclidean field theory. We then find that these two correlators are identical. This correspondence has already been shown graph by graph, but we give an alternative proof of it by direct calculation.

Thermal dark matter that couples more strongly to electrons and photons than to neutrinos will heat the electron-photon plasma relative to the neutrino background if it becomes nonrelativistic after the neutrinos decouple from the thermal background. This results in a reduction in $N_{\mathrm{eff}}$ below the standard model value, a result strongly disfavored by current CMB observations. Taking conservative lower bounds on $N_{\mathrm{eff}}$ and on the decoupling temperature of the neutrinos, we derive a bound on the dark matter particle mass of $m_{\chi }>3–9\mathrm{MeV}$, depending on the spin and statistics of the particle. For $p$-wave annihilation, our limit on the dark matter particle mass is stronger than the limit derived from distortions to the CMB fluctuation spectrum produced by annihilations near the epoch of recombination.

The Pierre Auger experiment has observed a few cosmic ray events above 55 EeV from the direction of the core of Cen A. These cosmic rays might have originated from the core of Cen A. High-energy gamma ray emission has been observed by HESS from the radio core and inner kpc jets of Cen A. We are testing whether pure hadronic interactions of protons or heavy nuclei with the matter in the core region or photodisintegration of heavy nuclei can explain the cosmic ray and high-energy gamma ray observations from the core of Cen A. The scenario of $p\mathrm{\text{−}}\gamma$ interactions followed by photopion decay has been tested earlier by Sahu et al. and found to be consistent with the observational results. In this paper, we have considered some other possibilities: (i) The primary cosmic rays at the core of Cen A are protons, and the high-energy gamma rays are produced in $p\mathrm{\text{−}}p$ interactions. (ii) The primary cosmic rays are Fe nuclei, and the high-energy gamma rays are produced in $\mathrm{Fe}\mathrm{\text{−}}p$ interactions. (iii) The primary cosmic rays are Fe nuclei, and they are photodisintegrated at the core. The daughter nuclei deexcite, and high-energy gamma rays are produced. The high-energy gamma ray fluxes expected in each of these cases are compared with the flux observed by the HESS experiment to normalize the spectrum of the primary cosmic rays at the core. We have calculated the expected number of cosmic ray nucleon events to be between 55 and 150 EeV in each of these cases to verify the consistencies of the different scenarios with the observations by the Pierre Auger experiment. We find that if the primary cosmic rays are Fe nuclei, then their photodisintegration followed by the deexcitation of daughter nuclei may explain the observed high-energy particle emissions from the core of Cen A. The luminosity of the cosmic ray Fe nuclei required to explain the observational results of HESS and Pierre Auger is higher than the luminosity of the cosmic ray protons in the $p\mathrm{\text{−}}\gamma$ interaction model. The required cosmic ray luminosity depends on the density of the low-energy photons at the source, which photodisintegrate the Fe nuclei, and the size of the emitting region.

In this article we compute the two-loop supersymmetric QCD corrections to Higgs-quark-quark couplings in the generic minimal supersymmetric standard model (MSSM) generated by diagrams involving squarks and gluinos. We give analytic results for the two-loop contributions in the limit of vanishing external momenta for general supersymmetry (SUSY) masses valid in the MSSM with general flavor structure. Working in the decoupling limit ($M_{\mathrm{SUSY}}\gg v$) we resum all chirally enhanced corrections (related to Higgs-quark-quark couplings) up to order ${\alpha }_s^{(n+1)}{tan}^n\beta$. This resummation allows for a more precise determination of the Yukawa coupling and Cabibbo-Kobayashi-Maskawa elements of the MSSM superpotential necessary for the study of Yukawa coupling unification. The knowledge of the Yukawa couplings of the MSSM superpotential in addition allows us to derive the effective Higgs-quark-quark couplings entering flavor changing neutral current processes. These effective vertices can in addition be used for the calculation of Higgs decays into quarks as long as $M_{\mathrm{SUSY}}>M_{\mathrm{Higgs}}$ holds. Furthermore, our calculation is also necessary for consistently including the chirally enhanced self-energy contributions into the calculation of flavor changing neutral current processes in the MSSM beyond leading order. At two-loop order, we find an enhancement of the supersymmetry threshold corrections, induced by the quark self-energies, of approximately 9% for $\mu =M_{\mathrm{SUSY}}$ compared to the one-loop result. At the same time, the matching scale dependence of the effective Higgs-quark-quark couplings is significantly reduced.