SU(3) Thermodynamics on Small Lattices

The free energy density of the SU(3) gauge theory at temperatures T/T_c = 4/3, 3/2 and 2 is calculated on lattices with temporal extent as small as N_t = 2, 3 and spatial extent N_s = 4 N_t using parametrized fixed point actions. Although cut-off effects are seen, they are hugely suppressed with respect to Wilson and Symanzik-improved actions and at N_t = 3 there is already a good agreement with the continuum limit as extrapolated from the results with the Wilson action at N_t = 6 and 8.Comment: 19 pages (latex text + 6 eps figures) in a uuencoded compressed tar fil

One-loop Reggeon-Reggeon-gluon vertex at arbitrary space-time dimension

In order to check the compatibility of the gluon Reggeization in QCD with the $s$-channel unitarity, the one-loop correction to the Reggeon-Reggeon-gluon vertex must be known at arbitrary space-time dimension $D$. We obtain this correction from the gluon production amplitude in the multi-Regge kinematics and present an explicit expression for it in terms of a few integrals over the transverse momenta of virtual particles. The one-gluon contribution to the non-forward BFKL kernel at arbitrary $D$ is also obtained.Comment: 22 pages, LaTe

Constrained Molecular Dynamics II: a N-body approach to nuclear systems

In this work we illustrate the basic development of the constrained molecular dynamics applied to the N-body problem in nuclear physics. The heavy computational taskes related to quantum effects, to the presence of the "hard core" repulsive interaction have been worked out by defining a set of transformations based on the concept of impulsive forces. In particular in the implemented version II of the Constrained Molecular Dynamics model the problem related to the non conservation of the total angular momentum has been solved. This problem can affect others semiclassical microscopic approaches as due to the "hard core" repulsive interaction or to the use of stochastic forces. The effect of the restored conservation law on the fusion cross section for 40Ca+40Ca system is also briefly discussed.Comment: Tex version 3.1459 (Web2C 7.3.1);main text+fig.cap in .tex 13 page; +4 figures .ps;the order and the numerical label of the figure files reflect the figure numbers in the main tex and captions, Submited to Journal of computational physic

Real-time extraction of growth rates from rotating substrates during molecular-beam epitaxy

We present a method for measuring molecular‐beam epitaxy growth rates in near real‐time on rotating substrates. This is done by digitizing a video image of the reflection high‐energy electron diffraction screen, automatically tracking and measuring the specular spot width, and using numerical techniques to filter the resulting signal. The digitization and image and signal processing take approximately 0.4 s to accomplish, so this technique offers the molecular‐beam epitaxy grower the ability to actively adjust growth times in order to deposit a desired layer thickness. The measurement has a demonstrated precision of approximately 2%, which is sufficient to allow active control of epilayer thickness by counting monolayers as they are deposited. When postgrowth techniques, such as frequency domain analysis, are also used, the reflection high‐energy electron diffraction measurement of layer thickness on rotating substrates improves to a precision of better than 1%. Since all of the components in the system described are commercially available, duplication is straightforward

Mueller-Navelet jets in high-energy hadron collisions

We consider within QCD collinear factorization the process $p+p\to {\rm jet} +{\rm jet} +X$, where two forward high-$p_T$ jets are produced with a large separation in rapidity $\Delta y$ (Mueller-Navelet jets [1]). The hard part of the reaction receives large higher-order corrections $\sim \alpha^n_s (\Delta y)^n$, which can be accounted for in the BFKL approach. We calculate cross section and azimuthal decorrelation, using the next-to-leading order jet vertices, in the small-cone approximation [2].Comment: 4 pages, 3 figures; presented at the International Workshop "Diffraction 2012", Puerto del Carmen (Spain), September 10-15, 201

Mass gap in the 2D O(3) non-linear sigma model with a theta=pi term

By analytic continuation to real theta of data obtained from numerical simulation at imaginary theta we study the Haldane conjecture and show that the O(3) non-linear sigma model with a theta term in 2 dimensions becomes massless at theta=3.10(5). A modified cluster algorithm has been introduced to simulate the model with imaginary theta. Two different definitions of the topological charge on the lattice have been used; one of them needs renormalization to match the continuum operator. Our work also offers a successful test for numerical methods based on analytic continuation.Comment: Latex file, 4 pages. To appear in PRD; it contains the justification of analicity, more details about the fits, more references, et