We show that a discrete exchange symmetry can give rise to realistic dark matter candidates in models with warped extra dimensions. We show how to realize our construction in a variety of models with warped extra dimensions and study in detail a realistic model of gauge-Higgs unification/composite Higgs in which the observed amount of dark matter is naturally reproduced. In this model, a realistic pattern of electroweak symmetry breaking typically occurs in a region of parameter space in which the fit to the electroweak precision observables improves, the Higgs is heavier than the experimental bound and new light quark resonances are predicted. We also quantify the fine-tuning of such scenarios, and discuss in which sense gauge-Higgs unification models result in a natural theory of electroweak symmetry breaking.

We investigate the $\kappa K^{*0}\gamma$-vertex in the framework of light cone QCD sum rules. We estimate the coupling constant ${\mathrm{g}}_{\kappa K^{*0}\gamma }$, and compare our result with that used in the nonlinear chiral Lagrangian approach using the vector-meson dominance model in the SU(3) limit.

A search for mixing in the neutral $D$ meson system has been performed using semileptonic $D^0\to K^{(*)-}{e}^{+}\nu$ and $D^0\to K^{(*)-}{\mu }^{+}\nu$ decays. Neutral $D$ mesons from $D^{*+}\to D^0{\pi }_s^{+}$ decays are used and the flavor at production is tagged by the charge of the slow pion. The measurement is performed using $492{\mathrm{fb}}^{-1}$ of data recorded by the Belle detector. From the yield of right-sign and wrong-sign decays arising from nonmixed and mixed events, respectively, we measure the ratio of the time-integrated mixing rate to the unmixed rate to be $R_M=(1.3\pm 2.2\pm 2.0)\times {10}^{-4}$. This corresponds to an upper limit of $R_M<6.1\times {10}^{-4}$ at the 90% C.L.

We compute Euclidean coordinate space correlation functions in a holographic model of QCD. We concentrate, in particular, on channels that are related to the $U(1{)}_A$ problem, the flavor-singlet axial vector, pseudoscalar meson, and pseudoscalar glueball (topological charge) correlator. We find that even a very simple holographic model defined on a slice of five-dimensional anti-de Sitter space provides a qualitatively correct description of QCD correlation functions. We study the role of anomaly terms, and show that both Euclidean positivity and low energy theorems based on the axial anomaly relation are correctly implemented. We compare the results with expectations from an instanton model of the QCD vacuum.

We construct and study a dimensionally reduced effective theory for high-temperature SU(2) Yang-Mills theory that respects all the symmetries of the underlying theory. Our main motivation is to study whether the correct treatment of the center symmetry can help extend the applicability of the dimensional reduction procedure towards the confinement transition. After performing perturbative matching to the full theory at asymptotically high temperatures, we map the phase diagram of the effective theory using nonperturbative lattice simulations. We find that at lower temperature the theory undergoes a second-order confining phase transition, in complete analogy with the full theory, which is a direct consequence of having incorporated the center symmetry.

In this article, we investigate inertial modes of rigidly rotating neutron stars, i.e. modes for which the Coriolis force is dominant. This is done using the assumption of a fixed spacetime (Cowling approximation). We present frequencies and eigenfunctions for a sequence of stars with a polytropic equation of state, covering a broad range of rotation rates. The modes were obtained with a nonlinear general relativistic hydrodynamic evolution code. We further show that the eigenequations for the oscillation modes can be written in a particularly simple form for the case of arbitrary fast but rigid rotation. Using these equations, we investigate some general characteristics of inertial modes, which are then compared to the numerically obtained eigenfunctions. In particular, we derive a rough analytical estimate for the frequency as a function of the number of nodes of the eigenfunction, and find that a similar empirical relation matches the numerical results with unexpected accuracy. We investigate the slow rotation limit of the eigenequations, obtaining two different sets of equations describing pressure and inertial modes. For the numerical computations we only considered axisymmetric modes, while the analytic part also covers nonaxisymmetric modes. The eigenfunctions suggest that the classification of inertial modes by the quantum numbers of the leading term of a spherical harmonic decomposition is artificial in the sense that the largest term is not strongly dominant, even in the slow rotation limit. The reason for the different structure of pressure and inertial modes is that the Coriolis force remains important in the slow rotation limit only for inertial modes. Accordingly, the scalar eigenequation we obtain in that limit is spherically symmetric for pressure modes, but not for inertial modes.

We present a global measurement of the integrated Sachs-Wolfe (ISW) effect obtained by cross correlating all relevant large-scale galaxy data sets with the cosmic microwave background radiation map provided by the Wilkinson Microwave Anisotropy Probe. With these measurements, the overall ISW signal is detected at the $\sim 4.5\sigma$ level. We also examine the cosmological implications of these measurements, particularly the dark energy equation of state $w$, its sound speed $c_s$, and the overall curvature of the Universe. The flat $\Lambda \mathrm{CDM}$ model is a good fit to the data and, assuming this model, we find that the ISW data constrain ${\Omega }_m={0.20}_{-0.11}^{+0.19}$ at the 95% confidence level. When we combine our ISW results with the latest baryon oscillation and supernovae measurements, we find that the result is still consistent with a flat $\Lambda \mathrm{CDM}$ model with $w=-1$ out to redshifts $z>1$.

The origin of both the diffuse high-latitude MeV gamma-ray emission and the 511 keV line flux from the Galactic bulge are uncertain. Previous studies have invoked dark matter physics to independently explain these observations, though as yet none has been able to explain both of these emissions within the well-motivated framework of weakly-interacting massive particles (WIMPs). Here we use an unstable WIMP dark matter model to show that it is in fact possible to simultaneously reconcile both of these observations, and in the process show a remarkable coincidence: decaying dark matter with MeV mass splittings can explain both observations if positrons and photons are produced with similar branching fractions. We illustrate this idea with an unstable branon, which is a standard WIMP dark matter candidate appearing in brane-world models with large extra dimensions. We show that because branons decay via three-body final states, they are additionally unconstrained by searches for Galactic MeV gamma-ray lines. As a result, such unstable long-lifetime dark matter particles provide novel and distinct signatures that can be tested by future observations of MeV gamma rays.

The extragalactic cosmic gamma-ray background (CGB) is an interesting channel to look for signatures of dark matter annihilation. In particular, besides the imprint in the energy spectrum, peculiar anisotropy patterns are expected compared to the case of a pure astrophysical origin of the CGB. We take into account the uncertainties in the dark matter clustering properties on subgalactic scales, deriving two possible anisotropy scenarios. A clear dark matter angular signature is achieved when the annihilation signal receives only a moderate contribution from subgalactic clumps and/or cuspy haloes. Experimentally, if galactic foreground systematics are efficiently kept under control, the angular differences are detectable with the forthcoming GLAST observatory, provided that the annihilation signal contributes to the CGB for a fraction $\gtrsim 10–20\%$. If, instead, subgalactic structures have a more prominent role, the astrophysical and dark matter anisotropies become degenerate, correspondingly diluting the dark matter signature. As complementary observables we also introduce the cross correlation between surveys of galaxies and the CGB and the cross correlation between different energy bands of the CGB, and we find that they provide a further sensitive tool to detect the dark matter angular signatures.

We investigate properties of attractors for the scalar field in the Lorentz violating scalar-vector-tensor theory of gravity. In this framework, both the effective coupling and potential functions determine the stabilities of the fixed points. In the model, we consider the constants of the slope of the effective coupling and potential functions which lead to the quadratic effective coupling vector with the (inverse) power-law potential. For the case of a purely scalar field, there are only two stable attractor solutions in the inflationary scenario. In the presence of a barotropic fluid, the fluid dominated solution is absent. We find two scaling solutions: the kinetic scaling solution and the scalar field scaling solutions. We show the stable attractors in regions of $(\gamma ,\xi )$ parameter space and in a phase plane plot for different qualitative evolutions. From the standard nucleosynthesis, we derive the constraints for the value of the coupling parameter.

In the minimal supersymmetric extension of the standard model (MSSM), if the two-Higgs doublets are lighter than some subset of the superpartners of the standard model particles, then it is possible to integrate out the heavy states to obtain an effective broken-supersymmetric low-energy Lagrangian. This Lagrangian can contain dimension-four gauge-invariant Higgs interactions that violate supersymmetry (SUSY). The wrong-Higgs Yukawa couplings generated by one-loop radiative corrections are a well-known example of this phenomenon. In this paper, we examine gauge-invariant gaugino-higgsino-Higgs boson interactions that violate supersymmetry. Such wrong-Higgs gaugino couplings can be generated in models of gauge-mediated SUSY-breaking in which some of the messenger fields couple to the MSSM Higgs bosons. In regions of parameter space where the messenger scale is low and $\tan \beta$ is large, these hard SUSY-breaking operators yield $\tan \beta$-enhanced corrections to tree-level supersymmetric relations in the chargino and neutralino sectors that can be as large as 56%. We demonstrate how physical observables in the chargino sector can be used to isolate the $\tan \beta$-enhanced effects derived from the wrong-Higgs gaugino operators.

We investigate the constraints on the anomalous $WWH$ couplings through the process $e^{-}\gamma \to {\nu }_e{W}^{-}H$. Considering incoming beam polarizations and the longitudinal and transverse polarization states of the final $W$ boson, we find 95% confidence level limits on the anomalous coupling parameters with an integrated luminosity of $500{\mathrm{fb}}^{-1}$ and $\sqrt{s}=0.5$ and 1 TeV energy. We show that initial beam and final state polarizations highly improve the sensitivity limits of the anomalous coupling parameters $b_W$ and ${\beta }_W$.

We study the production of the lightest neutralinos in the radiative process $e^{+}{e}^{-}\to {\tilde{\chi }}_1^0{\tilde{\chi }}_1^0\gamma$ in low energy supersymmetric models for the International Linear Collider energies. This includes the minimal supersymmetric standard model as well as its extension with an additional chiral Higgs singlet superfield, the nonminimal supersymmetric standard model. We compare and contrast the dependence of the signal cross section on the parameters of the neutralino sector of the minimal and nonminimal supersymmetric standard model. We also consider the background to this process coming from the standard model process $e^{+}{e}^{-}\to \nu \overline{\nu }\gamma$, as well as from the radiative production of the scalar partners of the neutrinos (sneutrinos) $e^{+}{e}^{-}\to \tilde{\nu }{\tilde{\nu }}^{*}\gamma$, which can be a background to the radiative neutralino production when the sneutrinos decay invisibly. In low energy supersymmetric models radiative production of the lightest neutralinos may be the only channel to study supersymmetric partners of the standard model particles at the first stage of a linear collider, since heavier neutralinos, charginos, and sleptons may be too heavy to be pair produced at a $e^{+}{e}^{-}$ machine with $\sqrt{s}=500\mathrm{GeV}$.

The nucleon electromagnetic form factors are calculated in a light cone QCD sum rules framework using the most general form of the nucleon interpolating current. Using two models for the distribution amplitudes, we predict the form factors. The predictions are also compared with existing experimental data. It is shown that our results describe remarkably well the existing experimental data.

The prompt ${\nu }_e$ burst from a core-collapse supernova is subject to both matter-induced flavor conversions and strong neutrino-neutrino refractive effects. For the lowest-mass progenitors, leading to O-Ne-Mg core supernovae, the matter density profile can be so steep that the usual Mikheyev-Smirnov-Wolfenstein matter effects occur within the dense-neutrino region close to the neutrino sphere. In this case a “split” occurs in the emerging spectrum, i.e., the ${\nu }_e$ flavor survival probability shows a steplike feature. We explain this feature analytically as a spectral split prepared by the Mikheyev-Smirnov-Wolfenstein effect. In a three-flavor treatment, the steplike feature actually consists of two narrowly spaced splits. They are determined by two combinations of flavor-lepton numbers that are conserved under collective oscillations.

Among all neutrino mixing parameters, the atmospheric neutrino mixing angle ${\theta }_{23}$ introduces the strongest variation on the flux ratios of ultrahigh-energy neutrinos. We investigate the potential of these flux ratio measurements at neutrino telescopes to constrain ${\theta }_{23}$. We consider astrophysical neutrinos originating from pion, muon-damped, and neutron sources and make a comparative study of their sensitivity reach to ${\theta }_{23}$. It is found that neutron sources are most favorable for testing deviations from maximal ${\theta }_{23}$. Using a ${\chi }^2$ analysis, we show, in particular, the power of combining (i) different flux ratios from the same type of source, and also (ii) combining flux ratios from different astrophysical sources. We include in our analysis “impure” sources, i.e., deviations from the usually assumed initial $(1:2:0)$, $(0:1:0)$, or $(1:0:0)$ flux compositions.

Even with recent progress, it is still very much an open question to understand how all compactification moduli are stabilized, since there are several mechanisms. For example, it is possible to generate a scalar potential either classically or through nonperturbative effects, such as gaugino condensation. Such a potential can stabilize certain of the moduli fields, for example, the dilaton. On the other hand, a background of thermal matter with moduli-dependent masses can also stabilize certain of the moduli, e.g., the radion. It is important to understand whether these two distinct mechanisms are compatible with each other, that is, that there are no interference terms that could spoil the moduli stabilization. In this paper, we study heterotic string theory on an $\mathcal{N}=1$ orbifold near an enhanced symmetry point. We then consider both a nonperturbatively generated potential and a gas of strings with moduli-dependent masses to stabilize the dilaton and radial modulus, respectively. We conclude that, given certain approximations, these two moduli stabilization mechanisms are compatible.

We examine the mesonic thermal spectrum of the Sakai-Sugimoto model of holographic QCD by finding the quasinormal frequencies of the supergravity dual. If flavor is added using D8-$\overline{\mathrm{D}8}$ branes there exist embeddings where the D-brane world volume contains a black hole. For these embeddings (the high-temperature phase of the Sakai-Sugimoto model) we determine the quasinormal spectra of scalar and vector mesons arising from the world volume Dirac-Born-Infeld (DBI) action of the D-brane. We stress the importance of a coordinate change that makes the infalling quasinormal modes regular at the horizon allowing a simple numerical shooting technique. Finally we examine the effect of finite spatial momentum on quasinormal spectra.

Inflationary models driven by a large number of axion fields are discussed in the context of type IIB compactifications with $\mathcal{N}=1$ supersymmetry. The inflatons arise as the scalar modes of the R-R two-forms evaluated on vanishing two-cycles in the compact geometry. The vanishing cycles are resolved by small two-volumes or NS-NS B fields which sit together with the inflatons in the same supermultiplets. String world sheets wrapping the vanishing cycles correct the metric of the R-R inflatons. They can help to generate kinetic terms close to the Planck scale and a mass hierarchy between the axions and their nonaxionic partners during inflation. At small string coupling, D-brane corrections are subleading in the metric of the R-R inflatons. However, an axion potential can be generated by D1 instantons or gaugino condensates on D5-branes. Models with a sufficiently large number of axions admit regions of chaotic inflation which can stretch over the whole axion field range for potentials from gaugino condensates. These models could allow for a possibly detectable amount of gravitational waves with tensor to scalar ratio as high as $r<0.14$.

We revisit the question of microcausality violations in quantum field theory on noncommutative spacetime, taking $\mathcal{O}(x)=\mathrm{\text{:}}\varphi \star \varphi \mathrm{\text{:}}(x)$ as a sample observable. Using methods of the theory of distributions, we precisely describe the support properties of the commutator $[\mathcal{O}(x),\mathcal{O}(y)]$ and prove that, in the case of space-space noncommutativity, it does not vanish at spacelike separation in the noncommuting directions. However, the matrix elements of this commutator exhibit a rapid falloff along an arbitrary spacelike direction irrespective of the type of noncommutativity. We also consider the star commutator for this observable and show that it fails to vanish even at spacelike separation in the commuting directions and completely violates causality. We conclude with a brief discussion about the modified Wightman functions which are vacuum expectation values of the star products of fields at different spacetime points.