There are quasiconformal theories, like the minimal and ultraminimal technicolor models, which may break dynamically the gauge symmetry of the standard model and at the same time are compatible with electroweak precision data. The main characteristic of this type of models is their fermionic content in one or more higher dimensional representations; therefore it is not immediately known which model leads to the most attractive channel or the minimum vacuum energy state. We discuss the effective potential for composite operators for these models, verifying that their vacuum energy values are different, with the ultraminimal model having a deeper minimum of energy.

In a variant of chiral color with the electroweak gauge group generalized to $SU(3{)}_L\times U(1)$ anomaly cancellation occurs more readily than in the $SU(2{)}_L\times U(1)$ case. Three families are required by anomaly cancellation and the top family appears nonsequentially.

We evaluate the shadowing effect in deeply virtual and real Compton scattering on nuclei in the framework of the color dipole model. We rely on the soft photon wave function derived in the instanton vacuum model and employ the impact parameter dependent phenomenological elastic dipole amplitude. Both the effects of quark and the gluon shadowing are taken into account.

The addition of an $A_4$ family symmetry and extended Higgs sector to the standard model can generate the tribimaximal mixing pattern for leptons, assuming the correct vacuum expectation value alignment of the Higgs scalars. Deviating this alignment affects the predictions for the neutrino oscillation and neutrino mass observables. An attempt is made to classify the plethora of models in the literature, with respect to the chosen $A_4$ particle assignments. Of these models, two particularly popular examples have been analyzed for deviations from tribimaximal mixing by perturbing the vacuum expectation value alignments. The effect of perturbations on the mixing angle observables is studied. However, it is only investigation of the mass-related observables (the effective mass for neutrinoless double beta decay and the sum of masses from cosmology) that can lead to the exclusion of particular models by constraints from future data, which indicates the importance of neutrino mass in disentangling models. The models have also been tested for fine-tuning of the parameters. Furthermore, a well-known seesaw model is generalized to include additional scalars, which transform as representations of $A_4$ not included in the original model.

In this brief report, we obtain the necessary and sufficient condition for a class of noncanonical single scalar field models to be exactly equivalent to barotropic perfect fluids, under the assumption of an irrotational fluid flow. An immediate consequence of this result is that the nonadiabatic pressure perturbation in this class of scalar field systems vanishes exactly at all orders in perturbation theory and on all scales. The Lagrangian for this general class of scalar field models depends on both the kinetic term and the value of the field. However, after a field redefinition, it can be effectively cast in the form of a purely kinetic k-essence model.

We provide a calculation of $N$-body ($N\ge 3$) nucleon interactions at short distances in holographic QCD. In the Sakai-Sugimoto model of large-$N_c$ massless QCD, $N$ baryons are described by $N$ Yang-Mills instantons in 5 spacetime dimensions. We compute a classical short-distance interaction Hamiltonian for $N$ ’t Hooft instantons. This corresponds to $N$ baryons sharing identical classical spins and isospins. We find that genuine $N$-body nuclear forces turn out to vanish for $N\ge 3$, at leading order. This suggests that classical $N$-body forces are always suppressed compared with 2-body forces.

We define various Born-Infeld gravity theories in $3+1$ dimensions which reduce to Hořava’s model at the quadratic level in small curvature expansion. In their exact forms, our actions provide $z\to \infty$ extensions of Hořava’s gravity, but when small curvature expansion is used, they reproduce finite $z$ models, including some half-integer ones.

We give an explicitly gauge-invariant canonical analysis of linearized quadratic gravity theories in three dimensions for both flat and de Sitter backgrounds. In flat backgrounds, we also study the effects of the gravitational Chern-Simons term, include the sources, and compute the weak field limit as well as scattering between spinning massive particles.

Coalescing massive black hole binaries are the strongest and probably the most important gravitational wave sources in the LISA band. The spin and orbital precessions bring complexity in the waveform and make the likelihood surface richer in structure as compared to the nonspinning case. We introduce an extended multimodal genetic algorithm which utilizes the properties of the signal and the detector response function to analyze the data from the third round of mock LISA data challenge (MLDC3.2). The performance of this method is comparable, if not better, to already existing algorithms. We have found all five sources present in MLDC3.2 and recovered the coalescence time, chirp mass, mass ratio, and sky location with reasonable accuracy. As for the orbital angular momentum and two spins of the black holes, we have found a large number of widely separated modes in the parameter space with similar maximum likelihood values.

We test general relativity (GR) using current cosmological data: the CMB from WMAP5 [E. Komatsu et al. (WMAP Collaboration), Astrophys. J. Suppl. Ser. 180, 330 (2009)], the integrated Sachs-Wolfe (ISW) effect from the cross correlation of the CMB with six galaxy catalogs [T. Giannantonio et al., Phys. Rev. D 77, 123520 (2008)], a compilation of supernovae (SNe) type Ia including the latest Sloan Digital Sky Survey SNe [R. Kessler et al., Astrophys. J. Suppl. Ser. 185, 32 (2009).], and part of the weak lensing (WL) data from the Canada-Franco-Hawaii Telescope Legacy Survey [L. Fu et al., Astron. Astrophys. 479, 9 (2008); M. Kilbinger et al., Astron. Astrophys. 497, 677 (2009).] that probe linear and mildly nonlinear scales. We first test a model in which the effective Newtonian constant $\mu$ and the ratio of the two gravitational potentials, $\eta$, transit from the GR value to another constant at late times; in this case, we find that GR is fully consistent with the combined data. The strongest constraint comes from the ISW effect which would arise from this gravitational transition; the observed ISW signal imposes a tight constraint on a combination of $\mu$ and $\eta$ that characterizes the lensing potential. Next, we consider four pixels in time and space for each function $\mu$ and $\eta$, and perform a principal component analysis, finding that seven of the resulting eight eigenmodes are consistent with GR within the errors. Only one eigenmode shows a $2\sigma$ deviation from the GR prediction, which is likely to be due to a systematic effect. However, the detection of such a deviation demonstrates the power of our time- and scale-dependent principal component analysis methodology when combining observations of structure formation and expansion history to test GR.

Differences in masses inferred from dynamics, such as velocity dispersions or x rays, and those inferred from lensing are a generic prediction of modified gravity theories. Viable models, however, must include some nonlinear mechanism to restore general relativity (GR) in dense environments, which is necessary to pass Solar System constraints on precisely these deviations. In this paper, we study the dynamics within virialized structures in the context of two modified gravity models, $f(R)$ gravity and Dvali-Gabadadze-Porrati (DGP). The nonlinear mechanisms to restore GR, which $f(R)$ and DGP implement in very different ways, have a strong impact on the dynamics in bound objects; they leave distinctive signatures in the dynamical mass-lensing mass relation as a function of mass and radius. We present measurements from $N$-body simulations of $f(R)$ and DGP, as well as semianalytical models that match the simulation results to surprising accuracy in both cases. The semianalytical models are useful for making the connection to observations. Our results confirm that the environment and scale dependence of the modified gravity effects have to be taken into account when confronting gravity theories with observations of dynamics in galaxies and clusters.

With LIGO having achieved its design sensitivity and the LIGO S5 strain data being available, constraints on the relic gravitational waves (RGWs) become realistic. The analytical spectrum of RGWs generated during inflation depends sensitively on the initial condition, which is generically described by the index $\beta$, the running index ${\alpha }_t$, and the tensor-to-scalar ratio $r$. By the LIGO S5 data of the cross-correlated two detectors, we obtain constraints on the parameters $(\beta ,{\alpha }_t,r)$. As a main result, we have computed the theoretical signal-to-noise ratio of RGWs for various values of $(\beta ,{\alpha }_t,r)$, using the cross-correlation for the given pair of LIGO detectors. The constraints by the indirect bound on the energy density of RGWs by big bang nucleosynthesis and cosmic microwave background have been obtained, which turn out to be still more stringent than LIGO S5.

A remarkabale $U(1)$ gauge extension of the supersymmetric standard model was proposed 8 years ago. It is anomaly free, has no $\mu$ term, and conserves baryon and lepton numbers automatically. The phenomenology of a specific version of this model is discussed. In particular, leptoquarks are predicted, with couplings to the heavy singlet neutrinos, the scalar partners of which may be components of dark matter. The Majorana neutrino mass matrix itself may have two zero subdeterminants.

We study the constraints on the mass-splitting of the first two generations of left-handed squarks obtained from $\Delta M_K$, ${ϵ}_K$ and $D-\overline{D}$ mixing. The different contributions from gluino, neutralino, and chargino diagrams are examined in detail, concluding that it is not justified to neglect electroweak gaugino diagrams if the squark mass matrices contain flavor nondiagonal left-left elements. We find that the constraints on the mass-splitting are very strong for light gluino masses. However, if the gluino is heavier than the squarks the constraints on the mass-splitting are much weaker. There are even large regions in parameter space where the different NP contributions cancel each other, leaving the mass splitting nearly unconstrained.

The analytical treatment of the nonperturbative QCD dynamics is one of the main open questions of the strong interactions. Currently, it is only possible to get some qualitative information about this regime considering other QCD-like theories, as, for example, the $N=4$ super Yang-Mills theory, where one can perform calculations in the nonperturbative limit of large ’t Hooft coupling using the anti–de Sitter space/conformal field theory (AdS/CFT). Recently, the high energy scattering amplitude was calculated in the AdS/CFT approach, applied to deep-inelastic scattering and confronted with the $F_2$ HERA data. In this work we extend the nonperturbative AdS/CFT inspired model for diffractive processes and compare its predictions with a perturbative approach based on the Balitsky-Kovchegov equation. We demonstrate that the AdS/CFT inspired model is not able to describe the current $F_2^{D(3)}$ HERA data and predicts a similar behavior to that from the Balitsky-Kovchegov equation in the range ${10}^{-7}\lesssim x_{\mathbb{P}}\lesssim {10}^{-4}$. At smaller values of $x_{\mathbb{P}}$ the diffractive structure function is predicted to be energy independent.

We show that ratios of tree and penguin amplitudes in $B\to K^{*}\pi$ and $B\to \rho K$ are 2 to 3 times larger than in $B\to K\pi$. This allows for considerably larger $CP$ asymmetries in the former processes than the 10% asymmetry measured in $B^0\to K^{+}{\pi }^{-}$. We study isospin sum rules for rate asymmetries in $B\to K\pi$, $K^{*}\pi$, $\rho K$, estimating small violation from interference of tree and electroweak penguin amplitudes. The breaking of the $K\pi$ asymmetry sum rule is estimated to be 1 to 2% and negative. Violation of $K^{*}\pi$ and $\rho K$ sum rules can be estimated from $B\to \rho \pi$ amplitudes using flavor SU(3), while breaking of a sum rule combining $K^{*}\pi$ and $\rho K$ asymmetries can be measured directly in a Dalitz analysis of $B^0\to K^{+}{\pi }^{-}{\pi }^0$. The three sum rules can be tested using complete sets of data taken at $e^{+}{e}^{-}$ $B$ factories and in experiments at the LHCb and at a future Super Flavor Factory, providing precision searches for new $\Delta S=\Delta I=1$ operators in the low-energy effective Hamiltonian.

We construct new families of nonsupersymmetric sourceless type IIA ${\mathrm{AdS}}_4$ vacua on those coset manifolds that also admit supersymmetric solutions. We investigate the spectrum of left-invariant modes and find that most, but not all, of the vacua are stable under these fluctuations. Generically, there are also no massless moduli.

We present a comprehensive investigation of cosmological constraints on the class of vector field formulations of modified gravity called generalized Einstein-aether models. Using linear perturbation theory we generate cosmic microwave background and large-scale structure spectra for general parameters of the theory, and then constrain them in various ways. We investigate two parameter regimes: a dark matter candidate where the vector field sources structure formation, and a dark energy candidate where it causes late-time acceleration. We find that the dark matter candidate does not fit the data, and identify five physical problems that can restrict this and other theories of dark matter. The dark energy candidate does fit the data, and we constrain its fundamental parameters; most notably we find that the theory’s kinetic index parameter $n_{\mathrm{ae}}$ can differ significantly from its $\Lambda \mathrm{CDM}$ value.

One of the sources of gravitational waves for the proposed space-based gravitational wave detector, the Laser Interferometer Space Antenna (LISA), are the inspirals of compact objects into supermassive black holes in the centers of galaxies—extreme-mass-ratio inspirals (EMRIs). Using LISA observations, we will be able to measure the parameters of each EMRI system detected to very high precision. However, the statistics of the set of EMRI events observed by LISA will be more important in constraining astrophysical models than extremely precise measurements for individual systems. The black holes to which LISA is most sensitive are in a mass range that is difficult to probe using other techniques, so LISA provides an almost unique window onto these objects. In this paper we explore, using Bayesian techniques, the constraints that LISA EMRI observations can place on the mass function of black holes at low redshift. We describe a general framework for approaching inference of this type—using multiple observations in combination to constrain a parametrized source population. Assuming that the scaling of the EMRI rate with the black-hole mass is known and taking a black-hole distribution given by a simple power law, $dn/d\ln M=A_0(M/M_{*}{)}^{{\alpha }_0}$, we find that LISA could measure the parameters to a precision of $\Delta (\ln A_0)\sim 0.08$, and $\Delta ({\alpha }_0)\sim 0.03$ for a reference model that predicts $\sim 1000$ events. Even with as few as 10 events, LISA should constrain the slope to a precision $\sim 0.3$, which is the current level of observational uncertainty in the low-mass slope of the black-hole mass function. We also consider a model in which $A_0$ and ${\alpha }_0$ evolve with redshift, but find that EMRI observations alone do not have much power to probe such an evolution.