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We use Floquet theory to study the maximum value of the stroboscopic group velocity in a one-dimensional tight-binding model subjected to an on-site staggered potential varying sinusoidally in time. The results obtained by numerically diagonalizing the Floquet operator are analyzed using a variety of analytical schemes. In the low-frequency limit we use adiabatic theory, while in the high-frequency limit the Magnus expansion of the Floquet Hamiltonian turns out to be appropriate. When the magnitude of the staggered potential is much greater or much less than the hopping, we use degenerate Floquet perturbation theory; we find that dynamical localization occurs in the former case when the maximum group velocity vanishes. Finally, starting from an "engineered" initial state where the particles (taken to be hard-core bosons) are localized in one part of the chain, we demonstrate that the existence of a maximum stroboscopic group velocity manifests in a light-cone-like spreading of the particles in real space. [ABSTRACT FROM AUTHOR]

Theories of physics beyond the standard model that address the hierarchy problem generally involve top partners, new particles that cancel the quadratic divergences associated with the Yukawa coupling of the Higgs boson to the top quark. With extensions of the standard model that involve new colored particles coming under strain from collider searches, scenarios in which the top partners carry no charge under the strong interactions have become increasingly compelling. Although elusive for direct searches, these theories predict modified couplings of the Higgs boson to the standard model particles. This results in corrections to the Higgs production and decay rates that can be detected at the LHC provided the top partners are sufficiently light, and the theory correspondingly natural. In this paper we consider three theories that address the little hierarchy problem and involve colorless top partners, specifically the mirror twin Higgs, folded supersymmetry, and the quirky little Higgs. For each model we investigate the current and future bounds on the top partners, and the corresponding limits on naturalness, that can be obtained from the Higgs program at the LHC. We conclude that the LHC will not be able to strongly disfavor naturalness, with mild tuning at the level of about one part in ten remaining allowed even with 3000 fb-1 of data at 14 TeV. [ABSTRACT FROM AUTHOR]

We present a novel analytic extraction of high-order post-Newtonian (pN) parameters that govern quasicircular binary systems. Coefficients in the pN expansion of the energy of a binary system can be found from corresponding coefficients in an extreme-mass-ratio inspiral computation of the change AU in the redshift factor of a circular orbit at fixed angular velocity. Remarkably, by computing this essentially gauge-invariant quantity to accuracy greater than one part in 10225, and by assuming that a subset of pN coefficients are rational numbers or products of Π and a rational, we obtain the exact analytic coefficients. We find the previously unexpected result that the post-Newtonian expansion of ΔU (and of the change ΔΩ in the angular velocity at fixed redshift factor) have conservative terms at half-integral pN order beginning with a 5.5 pN term. This implies the existence of a corresponding 5.5 pN term in the expansion of the energy of a binary system. Coefficients in the pN series that do not belong to the subset just described are obtained to accuracy better than 1 part in 10265-23n at rath pN order. We work in a radiation gauge, finding the radiative part of the metric perturbation from the gauge-invariant Weyl scalar Ψ0 via a Hertz potential. We use mode-sum renormalization, and find high-order renormalization coefficients by matching a series in L = l + 1/2 to the large-L behavior of the expression for ΔU. The nonradiative parts of the perturbed metric associated with changes in mass and angular momentum are calculated in the Schwarzschild gauge. [ABSTRACT FROM AUTHOR]