Within the context of a deformed theory of gravity, we consider a solution to the noncommutative Killing equations associated to a noncommutative $pp$-wave space-time.

Higher-order curvature corrections involving the conformally invariant Weyl-squared action have played a role in two recent investigations of four-dimensional gravity: in critical gravity, where they are added to the standard cosmological Einstein-Hilbert action with a coefficient tuned to make the massive ghostlike spin-2 excitations massless, and in a pure Weyl-squared action considered by Maldacena, where the massive spin-2 modes are removed by the imposition of boundary conditions. We exhibit the connections between the two approaches, and we also generalize critical gravity to a wider class of Weyl-squared modifications to cosmological Einstein gravity where one can eliminate the massive ghostlike spin-2 modes by means of boundary conditions. The cosmological constant plays a crucial role in the discussion, since there is then a “window” of negative mass-squared spin-2 modes around ${\mathrm{AdS}}_4$ that are not tachyonic. We also construct analogous conformal and nonconformal gravities in six dimensions.

We revisit previously developed analytic models for defect evolution and adapt them appropriately for the study of semilocal string networks. We thus confirm the expectation (based on numerical simulations) that linear scaling evolution is the attractor solution for a broad range of model parameters. We discuss in detail the evolution of individual semilocal segments, focusing on the phenomenology of segment growth, and also provide a preliminary comparison with existing numerical simulations.

Peculiar velocities change the expansion rate of any observer moving relative to the smooth Hubble flow. As a result, observers in a galaxy like our Milky Way can experience accelerated expansion within a globally decelerating universe, even when the drift velocities are small. The effect is local, but the affected scales can be large enough to give the false impression that the whole cosmos has recently entered an accelerating phase. Generally, peculiar velocities are also associated with dipolelike anisotropies, triggered by the fact that they introduce a preferred spatial direction. This implies that observers experiencing locally accelerated expansion, as a result of their own drift motion, may also find that the acceleration is maximized in one direction and minimized in the opposite. We argue that, typically, such a dipole anisotropy should be relatively small and the axis should probably lie fairly close to the one seen in the spectrum of the cosmic microwave background.

In this paper we derive, directly from the Nambu-Goto action, the relevant components of the acceleration of cosmological featureless $p$-branes, extending previous analysis based on the field theory equations in the thin-brane limit. The component of the acceleration parallel to the velocity is at the core of the velocity-dependent one-scale model for the evolution of $p$-brane networks. We use this model to show that, in a decelerating expanding universe in which the $p$-branes are relevant cosmologically, interactions cannot lead to frustration, except for fine-tuned nonrelativistic networks with a dimensionless curvature parameter $k\ll 1$. We discuss the implications of our findings for the cosmological evolution of $p$-brane networks.

Motivated by cosmological surveys that demand accurate theoretical modeling of the baryon acoustic oscillation (BAO) feature in galaxy clustering, we analyze N-body simulations in which a BAO-like Gaussian bump modulates the linear theory correlation function ${\xi }_L(r)=(r_0/r{)}^{n+3}$ of an underlying self-similar model with initial power spectrum $P(k)=A{k}^n$. These simulations test physical and analytic descriptions of BAO evolution far beyond the range of most studies, since we consider a range of underlying power spectra ($n=-0.5$, $-1$, $-1.5$) and evolve simulations to large effective correlation amplitudes (equivalent to ${\sigma }_8=4–12$ for $r_{\mathrm{bao}}=100h^{-1}\mathrm{Mpc}$). In all cases, nonlinear evolution flattens and broadens the BAO bump in $\xi (r)$ while approximately preserving its area. This evolution resembles a diffusion process in which the bump width ${\sigma }_{\mathrm{bao}}$ is the quadrature sum of the linear theory width and a length proportional to the rms relative displacement ${\Sigma }_{\mathrm{pair}}(r_{\mathrm{bao}})$ of particle pairs separated by $r_{\mathrm{bao}}$. For $n=-0.5$ and $n=-1$, we find no detectable shift of the location of the BAO peak, but the peak in the $n=-1.5$ model shifts steadily to smaller scales, following $r_{\mathrm{peak}}/r_{\mathrm{bao}}=1–1.08(r_0/r_{\mathrm{bao}}{)}^{1.5}$. The perturbation theory scheme of McDonald (2007) [P. McDonald, Phys. Rev. D 75, 043514 (2007).] and, to a lesser extent, standard 1-loop perturbation theory are fairly successful at explaining the nonlinear evolution of the Fourier power spectrum of our models. Analytic models also explain why the $\xi (r)$ peak shifts much more for $n=-1.5$ than for $n\ge -1$, though no ab initio model we have examined reproduces all of our numerical results. Simulations with $L_{\mathrm{box}}=10r_{\mathrm{bao}}$ and $L_{\mathrm{box}}=20r_{\mathrm{bao}}$ yield consistent results for $\xi (r)$ at the BAO scale, provided one corrects for the integral constraint imposed by the uniform density box.

We study the detectability of neutrino bursts from nearby direct black hole-forming collapses (failed supernovae) at Megaton (Mt) detectors. Because of their high energetics, these bursts could be identified—by the time coincidence of $N\ge 2$ or $N\ge 3$ events within a $\sim 1\mathrm{s}$ time window—from as far as $\sim 4–5\mathrm{Mpc}$ away. This distance encloses several supernova-rich galaxies, so that failed supernova bursts could be detected at a rate of up to one per decade, comparable to the expected rate of the more common, but less energetic, neutron star-forming collapses. Thus, the detection of a failed supernova within the lifetime of a Mt detector is realistic. It might give the first evidence of direct black hole formation, with important implications on the physics of this phenomenon.

An incomplete sky coverage poses difficulties in the extraction of the weak lensing information from the CMB. We test the reconstruction of the weak lensing convergence from CMB maps to which masks of point sources have been applied. We use the quadratic estimator with a kernel with finite support acting in real space for a Planck simulation. We recover the lensing signal without significant loss of power or addition of spurious correlations, thus showing that masking defected pixels does not affect the reconstruction of the weak lensing convergence in real space.

We formulate the Babinet Principle (BP) as a relation between scattering amplitudes and combine it with multiple scattering techniques to derive new properties of electromagnetic Casimir forces. We show that the Casimir force exerted by a planar conductor or dielectric on a self-complementary perforated planar mirror is approximately half that on a uniform mirror independent of the distance between them. Also, the BP suggests that Casimir edge effects are generically anomalously small. Furthermore, the BP can be used to relate any planar object to its complementary geometry, a relation we use to estimate Casimir forces between two screens with apertures.

We outline a field theory on a multifractal spacetime. The measure in the action is characterized by a varying Hausdorff dimension and logarithmic oscillations governed by a fundamental physical length. A fine hierarchy of length scales identifies different regimes, from a microscopic structure with discrete symmetries to an effectively continuum spacetime. Thanks to general arguments from fractal geometry, this scenario explicitly realizes two indirect or conjectured features of most quantum gravity models: a change of effective spacetime dimensionality with the probed scale, and the transition from a fundamentally discrete quantum spacetime to the continuum. It also allows us to probe ultramicroscopic scales where spectral methods based on ordinary geometry typically fail. Consequences for noncommutative field theories are discussed.

There are many charmless $B$ decay pairs whose amplitudes are related by U spin ($d\leftrightarrow s$) or flavor SU(3). The theoretical uncertainty in any analysis involving such pairs must take into account U-spin/SU(3) breaking. In the past, such considerations generally used theoretical input, but we show that this can be experimentally measured. We present lists of two- and three-body decay pairs from which the size of the breaking can be obtained. We detail the values of U-spin/SU(3) breaking given by the present experimental data. One pair—$B_d^0\to {\pi }^{+}{\pi }^{-}$ and $B_d^0\to {\pi }^{-}{K}^{+}$—may exhibit large nonfactorizable breaking, depending on the value taken for the $B_d^0\to {\pi }^{+}{\pi }^{-}$ direct $CP$ asymmetry. We present other signals of SU(3) breaking in two- and three-body decays, and discuss further tests for nonfactorizable effects. Finally, we also point out that the pure-penguin decay $B_s^0\to {\overline{K}}^0{\overline{K}}^0{K}^0$ is intriguing because it can be used to cleanly probe the $B_s^0\mathrm{\text{−}}{\overline{B}}_s^0$ mixing phase.

The set of coupled equations for the self-consistent propagator and the field expectation value is solved numerically with high accuracy in Euclidean space at zero temperature and in the broken symmetry phase of the ${\varphi }^4$ model. Explicitly finite equations are derived with the adaptation of the renormalization method of van Hees and Knoll [H. van Hees and J. Knoll, Phys. Rev. D 65, 025010 (2001).] to the case of nonvanishing field expectation value. The set of renormalization conditions used in this method leads to the same set of counterterms obtained recently by Patkós and Szép in [A. Patkós and Zs. Szép, Nucl. Phys. A811, 329 (2008).]. This makes possible the direct comparison of the accurate solution of explicitly finite equations with the solution of renormalized equations containing counterterms. The numerically efficient way of solving iteratively these latter equations is obtained by deriving at each order of the iteration new counterterms which evolve during the iteration process towards the counterterms determined based on the asymptotic behavior of the converged propagator. As shown at different values of the coupling, the use of these evolving counterterms accelerates the convergence of the solution of the equations.

In this paper we investigate the LHC potential for discovering doubly charged vector bileptons considering the measurable process $p$, $p\to e^{\mp }{e}^{\mp }{\mu }^{\pm }{\mu }^{\pm }X$. We perform the study using four different bilepton masses and three different exotics quark masses. Minimal LHC integrated luminosities needed for discovering and for setting limits on bilepton masses are obtained for both 7 and 14 TeV center-of-mass energies. We find that these spectacular signatures can be observed at the LHC in the next years up to a bilepton mass of order of 1 TeV.

Many beyond the standard model extensions predict the existence of heavy vectorlike fermions. We study the LHC signatures of one such heavy vectorlike fermion, called $b^{\prime }$, with electromagnetic charge $-1/3$ like the SM $b$-quark, but which could generically have different $SU(2{)}_L$ and $U(1{)}_Y$ quantum numbers. Our emphasis will be on the phenomenology due to $b\leftrightarrow b^{\prime }$ mass mixing, present after electroweak symmetry breaking. We focus on aspects which distinguish a vectorlike $b^{\prime }$ from a chiral $b^{\prime }$ and include tree-level decays of the $b^{\prime }$ into $tW$, $bZ$ and $bh$ final states. While our analysis is largely model independent, we take as a motivating example warped-space models in which a vectorlike $b^{\prime }$ appears as the custodial partner of the top-quark.

We examine several recent lattice-simulation data sets, asking whether they are consistent with infrared conformality. We observe, in particular, that for an $SU(3)$ gauge theory with 12 Dirac fermions in the fundamental representation, recent simulation data can be described assuming infrared conformality. Lattice simulations include a fermion mass $m$ that is then extrapolated to zero, and we note that this data can be fit by a small-$m$ expansion, allowing a controlled extrapolation. We also note that the conformal hypothesis does not work well for two theories that are known or expected to be confining and chirally broken, and that it does work well for another theory expected to be infrared conformal.

In the framework of the one-boson-exchange model, we have studied the interaction of the $B^{*}\overline{B}$ and $B^{*}{\overline{B}}^{*}$ systems. After considering the $S$-wave and $D$-wave mixing, we notice that both $Z_b(10610{)}^{\pm }$ and $Z_b(10650{)}^{\pm }$ can be interpreted as the $B^{*}\overline{B}$ and $B^{*}{\overline{B}}^{*}$ molecular states quite naturally. The long-range one-pion-exchange force alone is strong enough to form these loosely bound molecular states, which ensures the numerical results are quite model independent and robust.

We propose a novel way to break grand unified gauge symmetries via the Hosotani mechanism in models that can accommodate chiral fermions. Adjoint scalar fields are realized through the so-called diagonal embedding method which is often used in the heterotic string theory. We calculate the one-loop effective potential of the adjoint scalar field in a five dimensional model compactified on an $S^1/{\mathbb{Z}}_2$ orbifold, as an illustration. It turns out that the potential is basically the same as the one in an $S^1$ model, and thus the results in literatures, in addition to the chiral fermions, can be realized easily.

We present a successful inflation model based on $\lambda {\varphi }^4$ potential in which a standard model (SM) singlet inflaton $\varphi$, with mass of around a TeV or less, also plays the role of a weakly interacting scalar dark matter particle (WIMP). The WIMP relic abundance generated after inflation is in accord with the current observations. The spectral index $n_s$ lies within the Wilkinson Microwave Anisotropy Probe (WMAP) satellite $1\mathrm{\text{−}}\sigma$ bounds, while the Planck satellite may observe the tensor-to-scalar ratio, a canonical measure of gravity waves, which we estimate lies between 0.003 and 0.007. An unbroken $Z_2$ parity ensures that the scalar WIMP is absolutely stable.

We present results for a complete set of polarization observables for jet production in lepton-proton collision, where the final-state lepton is not observed. The calculations are carried out in collinear factorization at the level of Born diagrams. For all the observables we also provide numerical estimates for typical kinematics of a potential future electron-ion collider. On the basis of this numerical study, the prospects for the transverse single target spin asymmetry are particularly promising. This observable is given by a certain quark-gluon correlation function, which has a direct relation to the transverse momentum dependent Sivers parton distribution.

We study the scaling behavior of physical observables in strongly-flavored asymptotically free gauge theories, such as many-flavor QCD. Such theories approach a quantum critical point when the number of fermion flavors is increased. It is well-known that physical observables at this quantum critical point exhibit an exponential scaling behavior (Miransky scaling), provided the gauge coupling is considered as a constant external parameter. This scaling behavior is modified when the scale dependence of the gauge coupling is taken into account. Provided that the gauge coupling approaches an IR fixed point, we derive the resulting universal power-law corrections to the exponential scaling behavior and show that they are uniquely determined by the IR critical exponent of the gauge coupling. To illustrate our findings, we compute the universal corrections in many-flavor QCD with the aid of nonperturbative functional renormalization group methods. In this case, we expect the power-law scaling to be quantitatively more relevant if the theories are probed, for instance, at integer $N_{\mathrm{f}}$ as done in lattice simulations.