Electronic Quantum Monte Carlo Calculations of Atomic Forces, Vibrations, and Anharmonicities

Atomic forces are calculated for first-row monohydrides and carbon monoxide within electronic quantum Monte Carlo (QMC). Accurate and efficient forces are achieved by using an improved method for moving variational parameters in variational QMC. Newton's method with singular value decomposition (SVD) is combined with steepest descent (SD) updates along directions rejected by the SVD, after initial SD steps. Dissociation energies in variational and diffusion QMC agree well with experiment. The atomic forces agree quantitatively with potential energy surfaces, demonstrating the accuracy of this force procedure. The harmonic vibrational frequencies and anharmonicity constants, derived from the QMC energies and atomic forces, also agree well with experimental values.Comment: 6 pages, 2 figures; updated conten

Radio/X-ray Offsets of Large Scale Jets Caused by Synchrotron Time Lags

In the internal shock scenario, we argue that electrons in most kpc (or even larger) scale jets can be accelerated to energies high enough to emit synchrotron X-rays, if shocks exist on these scales. These high energy electrons emit synchrotron radiation at high frequencies and cool as they propagate downstream along the jet, emitting at progressively lower frequencies and resulting in time lags and hence radio/X-ray (and optical/X-ray if the optical knot is detectable) offsets at bright knots, with the centroids of X-ray knots being closer to the core. Taking into account strong effects of jet expansion, the behaviour of radio/X-ray and optical/X-ray offsets at bright knots in M87, Cen A, 3C 66B, 3C 31, 3C 273, and PKS 1127-145 is consistent with that of synchrotron time lags due to radiative losses. This suggests that the large scale X-ray and optical jets in these sources are due to synchrotron emission.Comment: 4 pages, Accepted for publication in ApJ Letter

Cosmic holographic bounds with UV and IR cutoffs

We introduce the cosmic holographic bounds with two UV and IR cutoff scales, to deal with both the inflationary universe in the past and dark energy in the future. To describe quantum fluctuations of inflation on sub-horizon scales, we use the Bekenstein-Hawking energy bound. However, it is not justified that the D-bound is satisfied with the coarse-grained entropy. The Hubble bounds are introduced for classical fluctuations of inflation on super-horizon scales. It turns out that the Hubble entropy bound is satisfied with the entanglement entropy and the Hubble temperature bound leads to a condition for the slow-roll inflation. In order to describe the dark energy, we introduce the holographic energy density which is the one saturating the Bekenstein-Hawking energy bound for a weakly gravitating system. Here the UV (IR) cutoff is given by the Planck scale (future event horizon), respectively. As a result, we find the close connection between quantum and classical fluctuations of inflation, and dark energy.Comment: 15page

Cosmological constraints from Gauss-Bonnet braneworld with large-field potentials

We calculate the spectral index and tensor-to-scalar ratio for patch inflation defined by $H^2\approx \beta^2_q V^q$ and $\dot{\phi}\approx -V'/3H$, using the slow-roll expansion. The patch cosmology arisen from the Gauss-Bonnet braneworld consists of Gauss-Bonnet (GB), Randall-Sundrum (RS), and 4D general relativistic (GR) cosmological models. In this work, we choose large-field potentials of $V=V_0\phi^p$ to compare with the observational data. Since second-order corrections are rather small in the slow-roll limit, the leading-order calculation is sufficient to compare with the data. Finally, we show that it is easier to discriminate between quadratic potential and quartic potential in the GB cosmological model rather than the GR or RS cosmological models.Comment: 13 pages, title changed, version to appear in JCA

BTZ black hole and quantum Hall effect in the bulk/boundary dynamics

We point out an interesting analogy between the BTZ black hole and QHE (Quantum Hall effect) in the (2+1)-dimensional bulk/boundary theories. It is shown that the Chern-Simons/Liouville(Chern-Simons/chiral boson) is an effective description for the BTZ black hole (QHE). Also the IR(bulk)-UV(boundary) connection for a black hole information bound is realized as the UV(low-lying excitations on bulk)-IR(long-range excitations on boundary) connection in the QHE. An inflow of conformal anomaly($c=1$ central charge) onto the timelike boundary of AdS$_3$ by the Noether current corresponds to an inflow of chiral anomaly onto the edge of disk by the Hall current.Comment: 8 pages, this version to appear in Phys. Rev.

U(1) Gauge Field of the Kaluza-Klein Theory in the Presence of Branes

We investigate the zero mode dimensional reduction of the Kaluza-Klein unifications in the presence of a single brane in the infinite extra dimension. We treat the brane as fixed, not a dynamical object, and do not require the orbifold symmetry. It seems that, contrary to the standard Kaluza-Klein models, the 4D effective action is no longer invariant under the U(1) gauge transformations due to the explicit breaking of isometries in the extra dimension by the brane. Surprisingly, however, the linearized perturbation analysis around the RS vacuum shows that the Kaluza-Klein gauge field does possess the U(1) gauge symmetry at the linear level. In addition, the graviscalar also behaves differently from the 4D point of view. Some physical implications of our results are also discussed.Comment: 10 pages, revtex, no figure, version to appear in Phys. Rev. D, possible caveats of our results due to the zero mode ansatz we used are explained in more detai

No absorption in de Sitter space

We study the wave equation for a minimally coupled massive scalar in D-dimensional de Sitter space. We compute the absorption cross section to investigate its cosmological horizon in the southern diamond. By analogy of the quantum mechanics, it is found that there is no absorption in de Sitter space. This means that de Sitter space is usually in thermal equilibrium, like the black hole in anti de Sitter space. It confirms that the cosmological horizon not only emits radiation but also absorbs that previously emitted by itself at the same rate, keeping the curvature radius of de Sitter space fixed.Comment: 11 pages, REVTE

Brane-Bulk Interaction and Holographic Principle

We introduce the brane-bulk interaction to discuss a limitation of the cosmological Cardy-Verlinde formula which is useful for the holographic description of brane cosmology. In the presence of the brane-bulk interaction, we cannot find the entropy representation of the first Friedmann equation (the cosmological Cardy-Verlinde formula). In the absence of the interaction, the cosmological Cardy-Verlinde formula is established even for the time-dependent charged AdS background. Hence, if there exists a dynamic exchange of energy between the brane and the bulk (that is, if $\tilde T^t~_y \not=0$), we cannot achieve the cosmological holographic principle on the brane.Comment: 9 pages, REVTE

Particle Kinematics in Horava-Lifshitz Gravity

We study the deformed kinematics of point particles in the Horava theory of gravity. This is achieved by considering particles as the optical limit of fields with a generalized Klein-Gordon action. We derive the deformed geodesic equation and study in detail the cases of flat and spherically symmetric (Schwarzschild-like) spacetimes. As the theory is not invariant under local Lorenz transformations, deviations from standard kinematics become evident even for flat manifolds, supporting superluminal as well as massive luminal particles. These deviations from standard behavior could be used for experimental tests of this modified theory of gravity.Comment: Added references, corrected a typing erro