119236957
Derrick’s theorem beyond a potential
Scalar field theories with derivative interactions are known to possess solitonic excitations, but such solitons are generally unsatisfactory because the effective theory fails precisely where nonlinearities responsible for the solitons are important. A new class of theories possessing (internal) galilean invariance can in principle bypass this difficulty. Here, we show that these galileon theories do not possess stable solitonic solutions. As a by-product, we show that no stable solitons exist for a different class of derivatively coupled theories, describing for instance the infrared dynamics of superfluids, fluids, solids and some k-essence models.
53143674
An effective theory for holographic RG flows
A bstractWe study the dilaton action induced by RG flows between holographic CFT fixed points. For this purpose we introduce a general bulk effective theory for the goldstone boson of the broken spacetime symmetry, providing an AdS analog of the EFT of Inflation. In two dimensions, we use the effective theory to compute the dilaton action, as well as the UV and IR conformal anomalies, without further assumptions. In higher dimensions we take a ‘slow-flow’ limit analogous to the assumption of slow-roll in Inflation, and in this context we obtain the dilaton action, focusing on terms proportional to the difference of the A-type anomalies. We include Gauss-Bonnet terms in the gravitational action in order to verify that our method correctly differentiates between A-type and other anomalies.
119194559
Solid Inflation
We develop a cosmological model where primordial inflation is driven by a ‘solid’, defined as a system of three derivatively coupled scalar fields obeying certain symmetries and spontaneously breaking a certain subgroup of these. The symmetry breaking pattern differs drastically from that of standard inflationary models: time translations are unbroken. This prevents our model from fitting into the standard effective field theory description of adiabatic perturbations, with crucial consequences for the dynamics of cosmological perturbations. Most notably, non-gaussianities in the curvature perturbations are unusually large, with fNL ∼ 1/( cs), and have a novel shape: peaked in the squeezed limit, with anisotropic dependence on how the limit is approached. Other unusual features include the absence of adiabatic fluctuation modes during inflation— which does not impair their presence and near scale-invariance after inflation—and a slightly blue tilt for the tensor modes.
118455503
Construction of the Conserved Non-linear Zeta via the Effective Action for Perfect Fluids
We consider the problem of how to construct the curvature perturbation $\zeta$ to nonlinear levels, which is expected to evolve time independently on super-horizon scales; in particular we concentrate on the situation where the universe is dominated by a perfect fluid. We have used a low energy/long wavelength effective action to model the fluid sector. Different from previous work, our approach assumes neither the absence of vector and tensor perturbations nor ``local homogeneity and isotropy''. As a corollary, we also show that the nonlinearly defined graviton field $\gamma_{ij}$ is conserved outside the horizon in the same manner as $\zeta$ is.
118441607
Dissipation in the effective field theory for hydrodynamics: First order effects
We introduce dissipative effects in the effective field theory of hydrodynamics. We do this in a model-independent fashion by coupling the long-distance degrees of freedom explicitly kept in the effective field theory to a generic sector that "lives in the fluid", which corresponds physically to the microscopic constituents of the fluid. At linear order in perturbations, the symmetries, the derivative expansion, and the assumption that this microscopic sector is thermalized, allow us to characterize the leading dissipative effects at low frequencies via three parameters only, which correspond to bulk viscosity, shear viscosity, and--in the presence of a conserved charge--heat conduction. Using our methods we re-derive the Kubo relations for these transport coefficients.
119105932
The quantum mechanics of perfect fluids
We consider the canonical quantization of an ordinary fluid. The resulting long-distance effective field theory is derivatively coupled, and therefore strongly coupled in the UV. The system however exhibits a number of peculiarities, associated with the vortex degrees of freedom. On the one hand, these have formally a vanishing strong-coupling energy scale, thus suggesting that the effective theory’s regime of validity is vanishingly narrow. On the other hand, we prove an analog of Coleman’s theorem, whereby the semiclassical vacuum has no quantum counterpart, thus suggesting that the vortex premature strong-coupling phenomenon stems from a bad identification of the ground state and of the perturbative degrees of freedom. Finally, vortices break the usual connection between short distances and high energies, thus potentially impairing the unitarity of the effective theory.
59428259
The upgrade of HLS linac control system
The linac control system of Hefei Light Source (HLS) was initially build in late 1980's, and a concerted effort has been put forth to upgrade it to a new, distributed one based on EPICS. Industrial PC based hardware is widely used as not only IOC but also front-end controller. Besides industrial PC, PLC and single-chip microcomputer are also used as front-end controllers in some subsystems. The software for industrial PC based front-end controller is developed based on vxWorks real-time operating system. The software for PLC and single-chip microcomputer are written with ladder software package and assemble language respectively. PC with Linux operating system and SUN workstation with Solaris operating system are used as operator interfaces. High level control is made up of some EPICS tools and Tcl/Tk scripts.
18827366
Spins of the Supermassive Black Hole in M87: New Constraints from TeV Observations
The rapid TeV gamma-ray variability detected in the well-known nearby radio galaxy M87 implies an extremely compact emission region (5-10 Schwarzschild radii) near the horizon of the supermassive black hole in the galactic center. TeV photons are affected by dilution due to interaction with the radiation field of the advection-dominated accretion flow (ADAF) around the black hole, and can thus be used to probe the innermost regions around the black hole. We calculate the optical depth of the ADAF radiation field to the TeV photons and find it strongly depends on the spin of the black hole. We find that transparent radii of 10 TeV photons are of 5R(S) and for the maximally rotating and nonrotating black holes, respectively. With the observations, the calculated 13R(S) transparent radii strongly suggest the black hole is spinning fast in the galaxy. TeV photons could be used as a powerful diagnostic for estimating black hole spins in galaxies in the future.
119220684
Search for the Signal of Monotop Production at the Early LHC
The main tasks of the LHC are to answer the fundamental questions in particle physics: whether the Higgs boson exist or not; are there new physics beyond the SM such as supersymmetry (SUSY), extra dimension, etc., at the TeV scale? The first stage of the LHC has discovered a scalar resonance closely resembling the SM Higgs boson, but provides no clue on the new physics beyond the SM.
118547314
Automatic computations at next-to-leading order in QCD for top-quark flavor-changing neutral processes
Computations at next-to-leading order in the Standard Model offer new technical challenges in presence of higher dimensional operators. We introduce a framework that, starting from the top-quark effective field theory at dimension six, allows to make predictions for cross sections as well as distributions in a fully automatic way. As an application, we present the first complete results at NLO in QCD for flavor changing neutral interactions including parton shower effects, for $tZ$, $th$, $t\gamma$ associated production at the LHC.
119241598
Central gas entropy excess as direct evidence for AGN feedback in galaxy groups and clusters
By analyzing Chandra X-ray data of a sample of 21 galaxy groups and 19 galaxy clusters, we find that in 31 sample systems there exists a significant central ( R ≤10 h -1 71 kpc) gas entropy excess (∆ K 0 ), which corresponds to ≃ 0.1 - 0.5 keV per gas particle, beyond the power-law model that best fits the radial entropy profile of the outer regions. We also find a distinct correlation between the central entropy excess ∆ K 0 and K-band luminosity LK of the central dominating galaxies (CDGs), which is scaled as ∆ K 0 ∝ L 1.6±0.4 K , where L K is tightly associated with the mass of the supermassive black hole hosted in the CDG. In fact, if an effective mass-to-energy conversion- efficiency of 0.02 is assumed for the accretion process, the cumulative AGN feedback E AGN feedback ≃ ηM BH c 2 yields an extra heating of ≃0.5 - 17.0 keV per particle, which is sufficient to explain the central entropy excess. In most cases, the AGN contribution can compensate the radiative loss of the X-ray gas within the cooling radius ( ≃0.002 - 2.2 keV per particle), and apparently exceeds the energy required to cause the scaling relations to deviate from the self-similar predictions ( ≃0.2 - 1.0 keV per particle). In contrast to the AGN feedback, the extra heating provided by supernova explosions accounts for ≃0.01 - 0.08 keV per particle in groups and is almost negligible in clusters. Therefore, the observed correlation between ∆ K 0 and L K can be considered as direct evidence for AGN feedback in galaxy groups and clusters.