We explore potential strategies for testing general relativity via the coherent motions of galaxies. Our position at $z=0$ provides the reference point for distance measures in cosmology. By contrast, the cosmic microwave background at $z\simeq 1100$ acts as the point of reference for the growth of a large-scale structure. As a result, we find there is a lack of synergy between growth and distance measures. We show that, when measuring the gravitational growth index $\gamma$ using redshift-space distortions, typically 80% of the signal corresponds to the local growth rate at the galaxy bin location, while the remaining fraction is determined by its behavior at higher redshifts. In order to clarify whether modified gravity may be responsible for the dark energy phenomenon, the aim is to search for a modification to the growth of structure. One might expect the magnitude of this deviation to be commensurate with the apparent dark energy density ${\Omega }_{\Lambda }(z)$. This provides an incentive to study redshift-space distortions at as low a redshift as is practical. Specifically, we find the region around $z=0.5$ offers the optimal balance of available volume and signal strength.

The bulk motion of galaxies induced by the growth of cosmic structure offers a rare opportunity to test the validity of general relativity across cosmological scales. However, modified gravity can be degenerate in its effect with the unknown values of cosmological parameters. More seriously, even the “observed” value of the redshift-space distortions used to measure the fluctuation growth rate depends on the assumed cosmological parameters (the Alcock-Paczynski effect). We give a full analysis of these issues, showing how to combine redshift-space distortions with baryon acoustic oscillations and CMB data, in order to obtain joint constraints on deviations from general relativity and on the equation of state of dark energy while allowing for factors such as nonzero curvature. In particular we note that the evolution of ${\Omega }_m(z)$, along with the Alcock-Paczynski effect, produces a degeneracy between the equation of state $w$ and the modified growth parameter $\gamma$. Typically, the total marginalized error on either of these parameters will be larger by a factor $\simeq 2$ compared to the conditional error where one or the other is held fixed. We argue that future missions should be judged by their figure of merit as defined in the $w_p-\gamma$ plane, and note that the inclusion of spatial curvature can degrade this value by an order of magnitude.

We argue that the occurrence of late-time acceleration can conveniently be described by first-order general relativity covariantly coupled to fermions. Dark energy arises as a Bardeen-Cooper-Schrieffer condensate of fermions which forms in the early universe. At late times, the gap and chemical potential evolve to have an equation of state with effective negative pressure, thus naturally leading to acceleration.

We consider an alternative to inflation for the generation of superhorizon perturbations in the Universe in which the speed of sound is faster than the speed of light. We label such cosmologies, first proposed by Armendariz-Picon, tachyacoustic, and explicitly construct examples of noncanonical Lagrangians which have superluminal sound speed, but which are causally self-consistent. Such models possess two horizons, a Hubble horizon and an acoustic horizon, which have independent dynamics. Even in a decelerating (noninflationary) background, a nearly scale-invariant spectrum of perturbations can be generated by quantum perturbations redshifted outside of a shrinking acoustic horizon. The acoustic horizon can be large or even infinite at early times, solving the cosmological horizon problem without inflation. These models do not, however, dynamically solve the cosmological flatness problem, which must be imposed as a boundary condition. Gravitational wave modes, which are produced by quantum fluctuations exiting the Hubble horizon, are not produced.

We study the transformation into a baryon asymmetry of a charge initially stored in a complex (waterfall) scalar field at the end of a hybrid inflation phase as described by Delepine, Martinez, and Urena-Lopez [Phys. Rev. Lett. 98, 161302 (2007)]. The waterfall field is coupled to right-handed neutrinos, and is also responsible for their Majorana masses. The charge is finally transferred to the leptons of the standard model through the decay of the right-handed neutrinos without introducing new $CP$ violating interactions. Other needed processes, like the decay of the inflaton field and the reheating of the Universe, are also discussed in detail.

I discuss a method to model the instrumental response of the CMS and ATLAS detectors at high missing transverse energy to dominant standard model $V+\mathrm{\text{jets}}$ backgrounds, where $V$ is a $Z$, $\gamma$ or $W$, using multijet QCD events. The method is developed for new physics searches in early data at the LHC with minimal recourse to simulation.

The inert doublet model is one of the simplest and most versatile scenarios for physics beyond the standard model. In this work, we examine the prospects for detecting the additional fields of this model at the LHC in the dilepton channel. We investigate a wide variety of theoretically and phenomenologically motivated benchmark scenarios, and show that within regions of model parameter space in which the dark-matter candidate is relatively light (between 40 and 80 GeV) and the mass splitting between the neutral scalars is also roughly 40–80 GeV, a signal at the $3\sigma$ to $12\sigma$ significance level can be observed with $100{\mathrm{fb}}^{-1}$ of integrated luminosity. In addition, even if the mass splitting between the neutral scalars is larger than $M_Z$, a signal of more than $3\sigma$ can be observed as long as the mass of the dark-matter candidate is around 40 GeV.

The chromoelectric and chromomagnetic fields, created by a static gluon-quark-antiquark system, are computed in quenched SU(3) lattice QCD, in a ${24}^3\times 48$ lattice at $\beta =6.2$ and $a=0.07261(85)\mathrm{fm}$. We compute the hybrid Wilson loop with two spatial geometries, one with a $U$ shape and another with an $L$ shape. The particular cases of the two-gluon glueball and quark-antiquark are also studied, and the Casimir scaling is investigated in a microscopic perspective. This microscopic study of the color fields is relevant to understanding the structure of hadrons, in particular, the hybrid excitation of mesons. This also contributes to understanding confinement with flux tubes and to discriminating between the models of fundamental versus adjoint confining strings, analogous to type-II and type-I superconductivity.

Dynamical gluon mass generation has been traditionally plagued with seagull divergences, and all regularization procedures proposed over the years yield finite but scheme-dependent gluon masses. In this work we show how such divergences can be eliminated completely by virtue of a characteristic identity, valid in dimensional regularization. The ability to trigger the aforementioned identity hinges crucially on the particular Ansatz employed for the three-gluon vertex entering into the Schwinger-Dyson equation governing the gluon propagator. The use of the appropriate three-gluon vertex brings about an additional advantage: one obtains two separate (but coupled) integral equations, one for the effective charge and one for the gluon mass. This system of integral equations has a unique solution, which unambiguously determines these two quantities. Most notably, the effective charge freezes in the infrared, and the gluon mass displays power-law running in the ultraviolet, in agreement with earlier considerations.

The pairwise production of neutral Higgs bosons $({\mathrm{h}}^0{\mathrm{A}}^0,{\mathrm{H}}^0{\mathrm{A}}^0)$ is analyzed in the context of the future linear colliders, such as the ILC and CLIC, within the general two-Higgs-doublet model (2HDM). The corresponding cross sections are computed at the one-loop level, including the full set of contributions at order $\mathcal{O}({\alpha }_{\mathrm{ew}}^3)$ together with the leading $\mathcal{O}({\alpha }_{\mathrm{ew}}^4)$ terms, in full compliance with the current phenomenological bounds and the stringent theoretical constraints inherent to the consistency of the model. We uncover regions across the 2HDM parameter space, mainly for low $\tan \beta \sim 1$ and moderate—and negative—values of the relevant ${\lambda }_5$ parameter, wherein the radiative corrections to the Higgs-pair production cross section, $\sigma ({\mathrm{e}}^{+}{\mathrm{e}}^{-}\to {\mathrm{A}}^0{\mathrm{h}}^0/{\mathrm{A}}^0{\mathrm{H}}^0)$, can comfortably reach $|\delta \sigma |/\sigma \sim 50\%$. This behavior can be traced back to the enhancement capabilities of the trilinear Higgs self-interactions—a trademark feature of the 2HDM, with no counterpart in the minimal supersymmetric standard model (MSSM). The corrections are strongly dependent on the actual value of ${\lambda }_5$ as well as on the Higgs mass spectrum. Interestingly enough, the quantum effects are positive for energies around $\sqrt{s}\simeq 500\mathrm{GeV}$, thereby producing a significant enhancement in the expected number of events precisely around the fiducial startup energy of the ILC. The Higgs-pair production rates can be substantial, typically a few tens of femtobarn, therefore amounting to a few thousand events per $500{\mathrm{fb}}^{-1}$ of integrated luminosity. In contrast, the corrections are negative in the highest energy range (viz. $\sqrt{s}\sim 1\mathrm{TeV}$ and above). We conclude that a precise measurement of the 2H final states could carry unambiguous footprints of an extended (nonsupersymmetric) Higgs sector. Finally, to better assess the scope of these effects, we compare the exclusive pairwise production of Higgs bosons with the inclusive gauge boson fusion channels leading to $2H+X$ final states, and also with the exclusive triple Higgs boson production. We find that these multiparticle final states can be highly complementary in the overall Higgs bosons search strategy.

We argue that the fermion masses and mixings are organized in a specific pattern. The approximately equal hierarchies between successive generations, the sizes of the mixing angles, the heaviness of just the top quark, and the approximate down-lepton equality can all be accommodated by many flavor models but can appear ad hoc. We present a simple, predictive mechanism to explain these patterns. All generations are treated democratically and the flavor symmetries are broken collectively by only two allowed couplings in flavor-space, a vector and matrix, with arbitrary $\mathcal{O}(1)$ entries. Repeated use of these flavor symmetry breaking spurions radiatively generates the Yukawa couplings with a natural hierarchy. We demonstrate this idea with two models in a split supersymmetric grand unified framework, with minimal additional particle content at the unification scale. Although flavor is generated at the grand unified theory scale, there are several potentially testable predictions. In our minimal model the usual prediction of exact $b\mathrm{\text{−}}\tau$ unification is replaced by the $SU(5)$ breaking relation $m_{\tau }/m_b=3/2$, in better agreement with observations. Other $SU(5)$ breaking effects in the fermion masses can easily arise directly from the flavor model itself. The symmetry breaking that triggers the generation of flavor necessarily gives rise to an axion, solving the strong $CP$ problem. These theories contain long-lived particles whose decays could give striking signatures at the LHC and may solve the primordial Lithium problems. These models also give novel proton decay signatures which can be probed by the next generation of experiments. Measurement of the various proton decay channels directly probes the flavor symmetry breaking couplings. In this scenario the Higgs mass is predicted to lie in a range near 150 GeV.

We simulate the possible emission from a disk perturbed by a recoiling supermassive black hole. To this end, we study radiation transfer from the system incorporating bremsstrahlung emission from a Maxwellian plasma and absorption given by Kramer’s opacity law modified to incorporate blackbody effects. We employ this model in the radiation transfer integration to compute the luminosity at several frequencies, and compare with previous bremsstrahlung luminosity estimations from a transparent limit (in which the emissivity is integrated over the computational domain and over all frequencies) and with a simple thermal emission model. We find close agreement between the radiation transfer results and the estimated bremsstrahlung luminosity from previous work for electromagnetic signals above ${10}^{14}\mathrm{Hz}$. For lower frequencies, we find a self-eclipsing behavior in the disk, resulting in a strong intensity variability connected to the orbital period of the disk.

We revisit the question of whether fluctuations in hydrodynamical, adiabatical matter could explain the observed structures in our Universe. We consider matter with variable equation of state $w=p_0/{\epsilon }_0$ and a concomitant (under the adiabatic assumption) density dependent speed of sound, $c_s$. We find a limited range of possibilities for a setup when modes start inside the Hubble radius, then leaving it and freezing out. For expanding universes, power-law $w({\epsilon }_0)$ models are ruled out (except when $c_s^2\propto w\ll 1$, requiring post-stretching the seeded fluctuations); but sharper profiles in $c_s$ do solve the horizon problem. Among these, a phase transition in $c_s$ is notable for leading to scale-invariant fluctuations if the initial conditions are thermal. For contracting universes all power-law $w({\epsilon }_0)$ solve the horizon problem, but only one leads to scale-invariance: $w\propto {\epsilon }_0^2$ and $c_s\propto {\epsilon }_0$. This model bypasses a number of problems with single scalar field cyclic models (for which $w$ is large but constant).

Dark matter decaying or annihilating into ${\mu }^{+}{\mu }^{-}$ or ${\tau }^{+}{\tau }^{-}$ has been proposed as an explanation for the $e^{\pm }$ anomalies reported by PAMELA and Fermi. Recent analyses show that IceCube, supplemented by DeepCore, will be able to significantly constrain the parameter space of decays to ${\mu }^{+}{\mu }^{-}$, and rule out decays to ${\tau }^{+}{\tau }^{-}$ and annihilations to ${\mu }^{+}{\mu }^{-}$ in less than five years of running. These analyses rely on measuring tracklike events in IceCube + DeepCore from down-going ${\nu }_{\mu }$. In this paper we show that by instead measuring cascade events, which are induced by all neutrino flavors, IceCube + DeepCore can rule out decays to ${\mu }^{+}{\mu }^{-}$ in only three years of running, and rule out decays to ${\tau }^{+}{\tau }^{-}$ and annihilation to ${\mu }^{+}{\mu }^{-}$ in only one year of running. These constraints are highly robust to the choice of dark matter halo profile and independent of dark matter-nucleon crosssection.

We update a previous investigation of cosmological effects of a nonstandard interaction between neutrinos and dark matter. Parametrizing the elastic-scattering cross section between the two species as a function of the temperature of the Universe, the resulting neutrino-dark matter fluid has a nonzero pressure, which determines diffusion-damped oscillations in the matter power spectrum similar to the acoustic oscillations generated by the photon-baryon fluid. Using cosmic microwave background data in combination with large scale structure experiment results, we then put constraints on the fraction of the interacting dark matter component as well as on the corresponding opacity.

We perform a global fit to the Cabibbo-Kobayashi-Maskawa unitarity triangle using the latest experimental and theoretical constraints. Our emphasis is on the hadronic weak matrix elements that enter the analysis, which must be computed using lattice QCD or other nonperturbative methods. Realistic lattice QCD calculations which include the effects of the dynamical up, down, and strange quarks are now available for all of the standard inputs to the global fit. We therefore present lattice averages for all of the necessary hadronic weak matrix elements. We attempt to account for correlations between lattice QCD results in a reasonable but conservative manner: whenever there are reasons to believe that an error is correlated between two lattice calculations, we take the degree of correlation to be 100%. These averages are suitable for use as inputs both in the global Cabibbo-Kobayashi-Maskawa unitarity triangle fit and other phenomenological analyses. In order to illustrate the impact of the lattice averages, we make standard model predictions for the parameters ${\widehat{B}}_K$, $|V_{cb}|$, and $|V_{ub}|/|V_{cb}|$. We find a $(2–3)\sigma$ tension in the unitarity triangle, depending upon whether we use the inclusive or exclusive determination of $|V_{cb}|$. If we interpret the tension as a sign of new physics in either neutral kaon or $B$ mixing, we find that the scenario with new physics in kaon mixing is preferred by present data.

We study a charged dilatonic black hole in ${\mathrm{AdS}}_5$, derived from a Lagrangian involving a gauge field whose kinetic term is modified by the exponential of a neutral scalar. This black hole has two properties which one might reasonably demand of the dual of a Fermi liquid: Its entropy is proportional to temperature at low temperature, and its extremal limit supports normal modes of massless, charged bulk fermions. The black hole we study has a simple analytic form because it can be embedded in type IIB string theory as the near-horizon limit of D3-branes with equal spins in two of the three independent transverse planes. Two further properties can be deduced from this embedding: There is a thermodynamic instability, reminiscent of ferromagnetism, at low temperatures; and there is an ${\mathrm{AdS}}_3$ factor in the extremal near-horizon geometry which accounts for the linear dependence of entropy on temperature. Altogether, it is plausible that the dilatonic black hole we study, or a relative of it with similar behavior in the infrared, is the dual of a Fermi liquid; however, the particular embedding in string theory that we consider is unlikely to have such a dual description, unless through some unexpected boson-fermion equivalence at large $N$.

As a step toward deeper understanding of the AdS/CFT correspondence, exact quantization of a Brink-Schwarz superparticle in the ${\mathrm{AdS}}_5\times S^5$ background with Ramond-Ramond flux is performed from the first principle in the phase space formulation. It includes the construction of the quantum Noether charges for the $psu(2,2|4)$ superconformal symmetry and by solving the superconformal primary conditions we obtain the complete physical spectrum of the system with the explicit wave functions. The spectrum agrees precisely with the supergravity results, including all the Kaluza-Klein excitations. Our method and the result are expected to shed light on the eventual quantization of a superstring in this important background.