Relevance of Chaos in Numerical Solutions of Quantum Billiards

In this paper we have tested several general numerical methods in solving the quantum billiards, such as the boundary integral method (BIM) and the plane wave decomposition method (PWDM). We performed extensive numerical investigations of these two methods in a variety of quantum billiards: integrable systens (circles, rectangles, and segments of circular annulus), Kolmogorov-Armold-Moser (KAM) systems (Robnik billiards), and fully chaotic systems (ergodic, such as Bunimovich stadium, Sinai billiard and cardiod billiard). We have analyzed the scaling of the average absolute value of the systematic error $\Delta E$ of the eigenenergy in units of the mean level spacing with the density of discretization $b$ (which is number of numerical nodes on the boundary within one de Broglie wavelength) and its relationship with the geometry and the classical dynamics. In contradistinction to the BIM, we find that in the PWDM the classical chaos is definitely relevant for the numerical accuracy at a fixed density of discretization $b$. We present evidence that it is not only the ergodicity that matters, but also the Lyapunov exponents and Kolmogorov entropy. We believe that this phenomenon is one manifestation of quantum chaos.Comment: 20 Revtex pages, 10 Eps figure

The Effective Fragment Molecular Orbital Method for Fragments Connected by Covalent Bonds

We extend the effective fragment molecular orbital method (EFMO) into treating fragments connected by covalent bonds. The accuracy of EFMO is compared to FMO and conventional ab initio electronic structure methods for polypeptides including proteins. Errors in energy for RHF and MP2 are within 2 kcal/mol for neutral polypeptides and 6 kcal/mol for charged polypeptides similar to FMO but obtained two to five times faster. For proteins, the errors are also within a few kcal/mol of the FMO results. We developed both the RHF and MP2 gradient for EFMO. Compared to ab initio, the EFMO optimized structures had an RMSD of 0.40 and 0.44 {\AA} for RHF and MP2, respectively.Comment: Revised manuscrip

Dynamical Aspects of Analogue Gravity: The Backreaction of Quantum Fluctuations in Dilute Bose-Einstein Condensates

We discuss the backreaction force exerted by quantum fluctuations in dilute Bose-Einstein condensates onto the motion of the classical background, derived by an ab initio approach from microscopic physics. It is shown that the effective-action method, widely employed in semiclassical quantum gravity, fails to give the full backreaction force. The failure of the effective-action method is traced back, inter alia, to the problem of the correct choice of the fundamental variables and the related operator ordering issues.Comment: 21+epsilon pages; has appeared in Springer Lecture Notes in Physic

Two-Loop Analysis of Non-abelian Chern-Simons Theory

Perturbative renormalization of a non-Abelian Chern-Simons gauge theory is examined. It is demonstrated by explicit calculation that, in the pure Chern-Simons theory, the beta-function for the coefficient of the Chern-Simons term vanishes to three loop order. Both dimensional regularization and regularization by introducing a conventional Yang-Mills component in the action are used. It is shown that dimensional regularization is not gauge invariant at two loops. A variant of this procedure, similar to regularization by dimensional reduction used in supersymmetric field theories is shown to obey the Slavnov-Taylor identity to two loops and gives no renormalization of the Chern-Simons term. Regularization with Yang-Mills term yields a finite integer-valued renormalization of the coefficient of the Chern-Simons term at one loop, and we conjecture no renormalization at higher order. We also examine the renormalization of Chern-Simons theory coupled to matter. We show that in the non-abelian case the Chern-Simons gauge field as well as the matter fields require infinite renormalization at two loops and therefore obtain nontrivial anomalous dimensions. We show that the beta function for the gauge coupling constant is zero to two-loop order, consistent with the topological quantization condition for this constant.Comment: 48 pages, UU/HEP/91/12; file format changed to standard Latex to solve the problem with printin

Verticalization of bacterial biofilms

Biofilms are communities of bacteria adhered to surfaces. Recently, biofilms of rod-shaped bacteria were observed at single-cell resolution and shown to develop from a disordered, two-dimensional layer of founder cells into a three-dimensional structure with a vertically-aligned core. Here, we elucidate the physical mechanism underpinning this transition using a combination of agent-based and continuum modeling. We find that verticalization proceeds through a series of localized mechanical instabilities on the cellular scale. For short cells, these instabilities are primarily triggered by cell division, whereas long cells are more likely to be peeled off the surface by nearby vertical cells, creating an "inverse domino effect". The interplay between cell growth and cell verticalization gives rise to an exotic mechanical state in which the effective surface pressure becomes constant throughout the growing core of the biofilm surface layer. This dynamical isobaricity determines the expansion speed of a biofilm cluster and thereby governs how cells access the third dimension. In particular, theory predicts that a longer average cell length yields more rapidly expanding, flatter biofilms. We experimentally show that such changes in biofilm development occur by exploiting chemicals that modulate cell length.Comment: Main text 10 pages, 4 figures; Supplementary Information 35 pages, 15 figure

Local and systemic immunomodulatory mechanisms triggered by Human Papillomavirus transformed cells: a potential role for G-CSF and neutrophils

Cervical cancer is the last stage of a series of molecular and cellular alterations initiated with Human Papillomavirus (HPV) infection. The process involves immune responses and evasion mechanisms, which culminates with tolerance toward tumor antigens. Our objective was to understand local and systemic changes in the interactions between HPV associated cervical lesions and the immune system as lesions progress to cancer. Locally, we observed higher cervical leukocyte infiltrate, reflected by the increase in the frequency of T lymphocytes, neutrophils and M2 macrophages, in cancer patients. We observed a strong negative correlation between the frequency of neutrophils and T cells in precursor and cancer samples, but not cervicitis. In 3D tumor cell cultures, neutrophils inhibited T cell activity, displayed longer viability and longer CD16 expression half-life than neat neutrophil cultures. Systemically, we observed higher plasma G-CSF concentration, higher frequency of immature low density neutrophils, and tolerogenic monocyte derived dendritic cells, MoDCs, also in cancer patients. Interestingly, there was a negative correlation between T cell activation by MoDCs and G-CSF concentration in the plasma. Our results indicate that neutrophils and G-CSF may be part of the immune escape mechanisms triggered by cervical cancer cells, locally and systemically, respectively.Tis study was supported by Sao Paulo Research foundation: grants 2008/57889-1, 2010/20010-4, 2014/19326-6, by the Brazilian National Counsel of Technological and Scientifc Development: grant 573799/2008-3. KLFA and RAMR had PhD fellowships by Sao Paulo Research Foundation, CRSF has a Coordination for the Improvement of Higher Education Personnel PhD fellowship. We thank the Pathology Department of the School of Medicine, coordinated by Prof. Venâncio Avancini Ferreira Alves, Universidade de São Paulo for the slides containing histological samples from the biopsies used in this study. We thank Sandra Alexandre Alves for her technical support.info:eu-repo/semantics/publishedVersio

On Slow Light as a Black Hole Analogue

Although slow light (electromagnetically induced transparency) would seem an ideal medium in which to institute a ``dumb hole'' (black hole analog), it suffers from a number of problems. We show that the high phase velocity in the slow light regime ensures that the system cannot be used as an analog displaying Hawking radiation. Even though an appropriately designed slow-light set-up may simulate classical features of black holes -- such as horizon, mode mixing, Bogoliubov coefficients, etc. -- it does not reproduce the related quantum effects. PACS: 04.70.Dy, 04.80.-y, 42.50.Gy, 04.60.-m.Comment: 14 pages RevTeX, 5 figure

Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)

The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08 ^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical, the second systematic and the third is associated to the ratio of fragmentation fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/- 0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table