The Holographic Models of the scalar sector of QCD

We investigate the AdS/QCD duality for the two-point correlation functions of the lowest dimension scalar meson and scalar glueball operators, in the case of the Soft Wall holographic model of QCD. Masses and decay constants as well as gluon condensates are compared to their QCD estimates. In particular, the role of the boundary conditions for the bulk-to-boundary propagators is emphasized.Comment: Invited talk at the 5th International Conference on Quarks and Nuclear Physics QNP'09, Beijing, China, 21-26 September 2009. To be published in Chinese Physics

Building a path-integral calculus: a covariant discretization approach

Path integrals are a central tool when it comes to describing quantum or thermal fluctuations of particles or fields. Their success dates back to Feynman who showed how to use them within the framework of quantum mechanics. Since then, path integrals have pervaded all areas of physics where fluctuation effects, quantum and/or thermal, are of paramount importance. Their appeal is based on the fact that one converts a problem formulated in terms of operators into one of sampling classical paths with a given weight. Path integrals are the mirror image of our conventional Riemann integrals, with functions replacing the real numbers one usually sums over. However, unlike conventional integrals, path integration suffers a serious drawback: in general, one cannot make non-linear changes of variables without committing an error of some sort. Thus, no path-integral based calculus is possible. Here we identify which are the deep mathematical reasons causing this important caveat, and we come up with cures for systems described by one degree of freedom. Our main result is a construction of path integration free of this longstanding problem, through a direct time-discretization procedure.Comment: 22 pages, 2 figures, 1 table. Typos correcte

Discrete modelling of capillary mechanisms in multi-phase granular media

A numerical study of multi-phase granular materials based upon micro-mechanical modelling is proposed. Discrete element simulations are used to investigate capillary induced effects on the friction properties of a granular assembly in the pendular regime. Capillary forces are described at the local scale through the Young-Laplace equation and are superimposed to the standard dry particle interaction usually well simulated through an elastic-plastic relationship. Both effects of the pressure difference between liquid and gas phases and of the surface tension at the interface are integrated into the interaction model. Hydraulic hysteresis is accounted for based on the possible mechanism of formation and breakage of capillary menisci at contacts. In order to upscale the interparticular model, triaxial loading paths are simulated on a granular assembly and the results interpreted through the Mohr-Coulomb criterion. The micro-mechanical approach is validated with a capillary cohesion induced at the macroscopic scale. It is shown that interparticular menisci contribute to the soil resistance by increasing normal forces at contacts. In addition, more than the capillary pressure level or the degree of saturation, our findings highlight the importance of the density number of liquid bonds on the overall behaviour of the material

The quadrupolar phases of the S=1 bilinear-biquadratic Heisenberg model on the triangular lattice

Using mean-field theory, exact diagonalizations and SU(3) flavour theory, we have precisely mapped out the phase diagram of the S=1 bilinear-biquadratic Heisenberg model on the triangular lattice in a magnetic field, with emphasis on the quadrupolar phases and their excitations. In particular, we show that ferroquadrupolar order can coexist with short-range helical magnetic order, and that the antiferroquadrupolar phase is characterized by a remarkable 2/3 magnetization plateau, in which one site per triangle retains quadrupolar order while the other two are polarized along the field. Implications for actual S=1 magnets are discussed.Comment: 4 pages, 5 figures, published versio

Stochastic perturbation of sweeping process and a convergence result for an associated numerical scheme

Here we present well-posedness results for first order stochastic differential inclusions, more precisely for sweeping process with a stochastic perturbation. These results are provided in combining both deterministic sweeping process theory and methods concerning the reflection of a Brownian motion. In addition, we prove convergence results for a Euler scheme, discretizing theses stochastic differential inclusions.Comment: 30 page

Convergence of fuzzy tori and quantum tori for the quantum Gromov–Hausdorff propinquity: An explicit approach

a

Neuroevolution and Machine Learning Research Applied to Connected Automated Vehicle and Powertrain Control

This dissertation focuses on advancing Predictive Energy Management (PrEM) functions applied to modern connected and automated vehicles (CAV) cohorts. PrEM aims to utilize connectivity and ADAS functions to adaptively minimize vehicle energy consumption in a wide array of operations, extending the original control designed around a reduced set of test cycle procedures to adapt to real-world stochastic operating conditions. This research document is built upon three journal publications covering two PrEM schemes; the global cohort and local vehicle optimization paths. Both optimal control solutions are generated using various Neuroevolution centric processes. Chapter 1 discusses the methods and reasoning behind the need to increase the development speed of readily implementable optimal control functions for both complex and system-of-systems (SoS) applications. Neuroevolution allows for fast development time, optimal design space exploration, high-fidelity modeling usage, and seamless integration with data science processes. It additionally enables real-time implementation without modification and requires a low compute footprint. This provides a new paradigm for future automotive product development where conventional adaptive and optimal techniques deployment is still lagging due to their complexity and shortcomings. At the global level, vehicle energy consumption is minimized by optimally controlling vehicle speed in diverse environments. Chapters 2 and 3 relate to connected traffic lights and uncontrolled intersection operations respectively. In the first study, the CAV cohort optimizes its velocity based on connected traffic light information. Thanks to the Traffic Technology Services (TTS) network, this information is shared via cellular communication. Energy consumption reduction of up to 22\% is reported using simulation and during closed-loop track testing. In the second study, no such timing information exists, and the cohorts must collaborate to enable safe operation at uncontrolled intersections. Here, the cohorts share states\u27 information to minimize deceleration and acceleration events for comfort and energy savings, primarily focusing on safety. Simulation demonstrates that effective collaboration can be achieved with cohorts\u27 lengths of up to 100 meters in congested environments. At the local PrEM level, additional energy savings can be achieved for each specific cohort\u27s vehicle based on its powertrain architecture. One of the more complex and relevant architectures to apply localized PrEM to are hybrid electric vehicles (HEV), where two sources of energy can be blended optimally based on a vehicle\u27s predicted speed profile, which is directly controlled by the global PrEM optimization function. In Chapter 4, Neuroevolution and vehicle speed profile classification is applied to a P3 HEV in demonstrating significant additional energy consumption improvements

Spectral analysis of the background in ground-based, long-slit spectroscopy

This paper examines the variations, because of atmospheric extinction, of broad-band visible spectra, obtained from long-slit spectroscopy, in the vicinity of some stars, nebulae, and one faint galaxy.Comment: 12 figure

Phase separation versus supersolid behavior in frustrated antiferromagnets

We investigate the competition between spin-supersolidity and phase separation in a frustrated spin-half model of weakly coupled dimers. We start by considering systems of hard-core bosons on the square lattice, onto which the low-energy physics of the herein investigated spin model can be mapped, and devise a criterion for gauging the interplay between supersolid order and domain wall formation based on strong coupling arguments. Effective bosonic models for the spin model are derived via the contractor renormalization (CORE) algorithm and we propose to combine a self-consistent cluster mean-field solution with our criterion for the occurrence of phase separation to derive the phase diagram as a function of frustration and magnetic field. In the limit of strong frustration, the model is shown to be unstable toward phase separation, in contradiction with recently published results. However, a region of stable supersolidity is identified for intermediate frustration, in a parameter range not investigated so far and of possible experimental relevance.Comment: 8 pages, 7 figures. Published versio