1,763 research outputs found
Algorithm for Computing Excited States in Quantum Theory
Monte Carlo techniques have been widely employed in statistical physics as
well as in quantum theory in the Lagrangian formulation. However, in the
conventional approach, it is extremely difficult to compute the excited states.
Here we present a different algorithm: the Monte Carlo Hamiltonian method,
designed to overcome the difficulties of the conventional approach. As a new
example, application to the Klein-Gordon field theory is shown.Comment: 3 pages, uses Latex and aipproc.cl
Development of improved cadmium electrodes for sealed secondary batteries Final report
Electrochemical behavior of fiber plaque materials compared with nickel powder sinter plaques in study to develop cadmium electrodes for sealed secondary batterie
Development of improved cadmium electrodes for sealed secondary batteries Interim report no. 1
Development of improved cadmium electrodes for sealed secondary batterie
Spectrum and Wave Functions of Excited States in Lattice Gauge Theory
We suggest a new method to compute the spectrum and wave functions of excited
states. We construct a stochastic basis of Bargmann link states, drawn from a
physical probability density distribution and compute transition amplitudes
between stochastic basis states. From such transition matrix we extract wave
functions and the energy spectrum. We apply this method to lattice
gauge theory. As a test we compute the energy spectrum, wave functions and
thermodynamical functions of the electric Hamiltonian and compare it with
analytical results. We find excellent agreement. We observe scaling of energies
and wave functions in the variable of time. We also present first results on a
small lattice for the full Hamiltonian including the magnetic term.Comment: Lattice 2008 conferenc
The Fractal Geometry of Critical Systems
We investigate the geometry of a critical system undergoing a second order
thermal phase transition. Using a local description for the dynamics
characterizing the system at the critical point T=Tc, we reveal the formation
of clusters with fractal geometry, where the term cluster is used to describe
regions with a nonvanishing value of the order parameter. We show that,
treating the cluster as an open subsystem of the entire system, new
instanton-like configurations dominate the statistical mechanics of the
cluster. We study the dependence of the resulting fractal dimension on the
embedding dimension and the scaling properties (isothermal critical exponent)
of the system. Taking into account the finite size effects we are able to
calculate the size of the critical cluster in terms of the total size of the
system, the critical temperature and the effective coupling of the long
wavelength interaction at the critical point. We also show that the size of the
cluster has to be identified with the correlation length at criticality.
Finally, within the framework of the mean field approximation, we extend our
local considerations to obtain a global description of the system.Comment: 1 LaTeX file, 4 figures in ps-files. Accepted for publication in
Physical Review
Modelling predictors of molecular response to frontline imatinib for patients with chronic myeloid leukaemia
BACKGROUND: Treatment of patients with chronic myeloid leukaemia (CML) has become increasingly difficult in recent years due to the variety of treatment options available and challenge deciding on the most appropriate treatment strategy for an individual patient. To facilitate the treatment strategy decision, disease assessment should involve molecular response to initial treatment for an individual patient. Patients predicted not to achieve major molecular response (MMR) at 24 months to frontline imatinib may be better treated with alternative frontline therapies, such as nilotinib or dasatinib. The aims of this study were to i) understand the clinical prediction 'rules' for predicting MMR at 24 months for CML patients treated with imatinib using clinical, molecular, and cell count observations (predictive factors collected at diagnosis and categorised based on available knowledge) and ii) develop a predictive model for CML treatment management. This predictive model was developed, based on CML patients undergoing imatinib therapy enrolled in the TIDEL II clinical trial with an experimentally identified achieving MMR group and non-achieving MMR group, by addressing the challenge as a machine learning problem. The recommended model was validated externally using an independent data set from King Faisal Specialist Hospital and Research Centre, Saudi Arabia. PRINCIPLE FINDINGS: The common prognostic scores yielded similar sensitivity performance in testing and validation datasets and are therefore good predictors of the positive group. The G-mean and F-score values in our models outperformed the common prognostic scores in testing and validation datasets and are therefore good predictors for both the positive and negative groups. Furthermore, a high PPV above 65% indicated that our models are appropriate for making decisions at diagnosis and pre-therapy. Study limitations include that prior knowledge may change based on varying expert opinions; hence, representing the category boundaries of each predictive factor could dramatically change performance of the models.Haneen Banjar, Damith Ranasinghe, Fred Brown, David Adelson, Trent Kroger, Tamara Leclercq, Deborah White, Timothy Hughes, Naeem Chaudhr
Spontaneous Symmetry Breaking of phi4(1+1) in Light Front Field Theory
We study spontaneous symmetry breaking in phi^4_(1+1) using the light-front
formulation of the field theory. Since the physical vacuum is always the same
as the perturbative vacuum in light-front field theory the fields must develop
a vacuum expectation value through the zero-mode components of the field. We
solve the nonlinear operator equation for the zero-mode in the one-mode
approximation. We find that spontaneous symmetry breaking occurs at
lambda_critical = 4 pi(3+sqrt 3), which is consistent with the value
lambda_critical = 54.27 obtained in the equal time theory. We calculate the
value of the vacuum expectation value as a function of the coupling constant in
the broken phase both numerically and analytically using the delta expansion.
We find two equivalent broken phases. Finally we show that the energy levels of
the system have the expected behavior within the broken phase.Comment: 17 pages, OHSTPY-HEP-TH-92-02
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