1,280 research outputs found
Coherent States Formulation of Polymer Field Theory
We introduce a stable and efficient complex Langevin (CL) scheme to enable
the first numerical simulations of the coherent-states (CS) formulation of
polymer field theory. In contrast with Edwards' well known auxiliary-field (AF)
framework, the CS formulation does not contain an embedded non-linear,
non-local functional of the auxiliary fields, and the action of the field
theory has a fully explicit, finite-order and semi-local polynomial character.
In the context of a polymer solution model, we demonstrate that the new CS-CL
dynamical scheme for sampling fluctuations in the space of coherent states
yields results in good agreement with now-standard AF simulations. The
formalism is potentially applicable to a broad range of polymer architectures
and may facilitate systematic generation of trial actions for use in
coarse-graining and numerical renormalization-group studies.Comment: 14pages 8 figure
Stochastic Differential Equations for Quantum Dynamics of Spin-Boson Networks
The quantum dynamics of open many-body systems poses a challenge for
computational approaches. Here we develop a stochastic scheme based on the
positive P phase-space representation to study the nonequilibrium dynamics of
coupled spin-boson networks that are driven and dissipative. Such problems are
at the forefront of experimental research in cavity and solid state
realizations of quantum optics, as well as cold atom physics, trapped ions and
superconducting circuits. We demonstrate and test our method on a driven,
dissipative two-site system, each site involving a spin coupled to a photonic
mode, with photons hopping between the sites, where we find good agreement with
Monte Carlo Wavefunction simulations. In addition to numerically reproducing
features recently observed in an experiment [Phys. Rev. X 4, 031043 (2014)], we
also predict a novel steady state quantum dynamical phase transition for an
asymmetric configuration of drive and dissipation.Comment: 15 pages, 8 figure
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Analysis of gas chromatography/mass spectrometry data for catalytic lignin depolymerization using positive matrix factorization
Various catalytic technologies are being developed to efficiently convert lignin into renewable chemicals. However, due to its complexity, catalytic lignin depolymerization often generates a wide and complex distribution of product compounds. Gas chromatography/mass spectrometry (GC-MS) is a common analytical technique to profile the compounds that comprise lignin depolymerization products. GC-MS is applied not only to determine the product composition, but also to develop an understanding of the catalytic reaction pathways and of the relationships among catalyst structure, reaction conditions, and the resulting compounds generated. Although a very useful tool, the analysis of lignin depolymerization products with GC-MS is limited by the quality and scope of the available mass spectral libraries and the ability to correlate changes in GC-MS chromatograms to changes in lignin structure, catalyst structure, and other reaction conditions. In this study, the GC-MS data of the depolymerization products generated from organosolv hybrid poplar lignin using a copper-doped porous metal oxide catalyst and a methanol/dimethyl carbonate co-solvent was analyzed by applying a factor analysis technique, positive matrix factorization (PMF). Several different solutions for the PMF model were explored. A 13-factor solution sufficiently explains the chemical changes occurring to lignin depolymerization products as a function of lignin, reaction time, catalyst, and solvent. Overall, seven factors were found to represent aromatic compounds, while one factor was defined by aliphatic compounds
A Multiresolution Stochastic Process Model for Predicting Basketball Possession Outcomes
Basketball games evolve continuously in space and time as players constantly
interact with their teammates, the opposing team, and the ball. However,
current analyses of basketball outcomes rely on discretized summaries of the
game that reduce such interactions to tallies of points, assists, and similar
events. In this paper, we propose a framework for using optical player tracking
data to estimate, in real time, the expected number of points obtained by the
end of a possession. This quantity, called \textit{expected possession value}
(EPV), derives from a stochastic process model for the evolution of a
basketball possession; we model this process at multiple levels of resolution,
differentiating between continuous, infinitesimal movements of players, and
discrete events such as shot attempts and turnovers. Transition kernels are
estimated using hierarchical spatiotemporal models that share information
across players while remaining computationally tractable on very large data
sets. In addition to estimating EPV, these models reveal novel insights on
players' decision-making tendencies as a function of their spatial strategy.Comment: 31 pages, 9 figure
Factorization at the LHC: From PDFs to Initial State Jets
We study proton-(anti)proton collisions at the LHC or Tevatron in the
presence of experimental restrictions on the hadronic final state and for
generic parton momentum fractions. At the scale Q of the hard interaction,
factorization does not yield standard parton distribution functions (PDFs) for
the initial state. The measurement restricting the hadronic final state
introduces a new scale \mu_B << Q and probes the proton prior to the hard
collision. This corresponds to evaluating the PDFs at the scale \mu_B. After
the proton is probed, the incoming hard parton is contained in an initial-state
jet, and the hard collision occurs between partons inside these jets rather
than inside protons. The proper description of such initial-state jets requires
"beam functions". At the scale \mu_B, the beam function factorizes into a
convolution of calculable Wilson coefficients and PDFs. Below \mu_B, the
initial-state evolution is described by the usual PDF evolution which changes
x, while above \mu_B it is governed by a different renormalization group
evolution which sums double logarithms of \mu_B/Q and leaves x fixed. As an
example, we prove a factorization theorem for "isolated Drell-Yan", pp -> Xl+l-
where X is restricted to have no central jets. We comment on the extension to
cases where the hadronic final state contains a certain number of isolated
central jets.Comment: 41 pages (19 for everyone + 22 for experts), 16 figures; v2:
Notational typos fixed. Added sentences to emphasize that measuring isolated
Drell-Yan directly tests the initial state parton shower; v3: typos fixed,
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