1,840 research outputs found
The Pivotal Role of Causality in Local Quantum Physics
In this article an attempt is made to present very recent conceptual and
computational developments in QFT as new manifestations of old and well
establihed physical principles. The vehicle for converting the
quantum-algebraic aspects of local quantum physics into more classical
geometric structures is the modular theory of Tomita. As the above named
laureate to whom I have dedicated has shown together with his collaborator for
the first time in sufficient generality, its use in physics goes through
Einstein causality. This line of research recently gained momentum when it was
realized that it is not only of structural and conceptual innovative power (see
section 4), but also promises to be a new computational road into
nonperturbative QFT (section 5) which, picturesquely speaking, enters the
subject on the extreme opposite (noncommutative) side.Comment: This is a updated version which has been submitted to Journal of
Physics A, tcilatex 62 pages. Adress: Institut fuer Theoretische Physik
FU-Berlin, Arnimallee 14, 14195 Berlin presently CBPF, Rua Dr. Xavier Sigaud
150, 22290-180 Rio de Janeiro, Brazi
Bondi-Metzner-Sachs symmetry, holography on null-surfaces and area proportionality of "light-slice" entropy
It is shown that certain kinds of behavior, which hitherto were expected to
be characteristic for classical gravity and quantum field theory in curved
spacetime, as the infinite dimensional Bondi-Metzner-Sachs symmetry, holography
on event horizons and an area proportionality of entropy, have in fact an
unnoticed presence in Minkowski QFT. This casts new light on the fundamental
question whether the volume propotionality of heat bath entropy and the
(logarithmically corrected) dimensionless area law obeyed by
localization-induced thermal behavior are different geometric parametrizations
which share a common primordeal algebraic origin. Strong arguments are
presented that these two different thermal manifestations can be directly
related, this is in fact the main aim of this paper. It will be demonstrated
that QFT beyond the Lagrangian quantization setting receives crucial new
impulses from holography onto horizons. The present paper is part of a project
aimed at elucidating the enormous physical range of "modular localization". The
latter does not only extend from standard Hamitonian heat bath thermal states
to thermal aspects of causal- or event- horizons addressed in this paper. It
also includes the recent understanding of the crossing property of formfactors
whose intriguing similarity with thermal properties was, although sometimes
noticed, only sufficiently understood in the modular llocalization setting.Comment: 42 pages, changes, addition of new results and new references, in
this form the paper will appear in Foundations of Physic
Generalized Particle Statistics in Two-Dimensions: Examples from the Theory of Free Massive Dirac Field
In the framework of algebraic quantum field theory we analyze the anomalous
statistics exhibited by a class of automorphisms of the observable algebra of
the two-dimensional free massive Dirac field, constructed by fermionic gauge
group methods. The violation of Haag duality, the topological peculiarity of a
two-dimensional space-time and the fact that unitary implementers do not lie in
the global field algebra account for strange behaviour of statistics, which is
no longer an intrinsic property of sectors. Since automorphisms are not inner,
we exploit asymptotic abelianness of intertwiners in order to construct a
braiding for a suitable -tensor subcategory of End(). We
define two inequivalent classes of path connected bi-asymptopias, selecting
only those sets of nets which yield a true generalized statistics operator.Comment: 24 page
Causality and dispersion relations and the role of the S-matrix in the ongoing research
The adaptation of the Kramers-Kronig dispersion relations to the causal
localization structure of QFT led to an important project in particle physics,
the only one with a successful closure. The same cannot be said about the
subsequent attempts to formulate particle physics as a pure S-matrix project.
The feasibility of a pure S-matrix approach are critically analyzed and their
serious shortcomings are highlighted. Whereas the conceptual/mathematical
demands of renormalized perturbation theory are modest and misunderstandings
could easily be corrected, the correct understanding about the origin of the
crossing property requires the use of the mathematical theory of modular
localization and its relation to the thermal KMS condition. These new concepts,
which combine localization, vacuum polarization and thermal properties under
the roof of modular theory, will be explained and their potential use in a new
constructive (nonperturbative) approach to QFT will be indicated. The S-matrix
still plays a predominant role but, different from Heisenberg's and
Mandelstam's proposals, the new project is not a pure S-matrix approach. The
S-matrix plays a new role as a "relative modular invariant"..Comment: 47 pages expansion of arguments and addition of references,
corrections of misprints and bad formulation
Estimation and uncertainty of reversible Markov models
Reversibility is a key concept in Markov models and Master-equation models of
molecular kinetics. The analysis and interpretation of the transition matrix
encoding the kinetic properties of the model relies heavily on the
reversibility property. The estimation of a reversible transition matrix from
simulation data is therefore crucial to the successful application of the
previously developed theory. In this work we discuss methods for the maximum
likelihood estimation of transition matrices from finite simulation data and
present a new algorithm for the estimation if reversibility with respect to a
given stationary vector is desired. We also develop new methods for the
Bayesian posterior inference of reversible transition matrices with and without
given stationary vector taking into account the need for a suitable prior
distribution preserving the meta- stable features of the observed process
during posterior inference. All algorithms here are implemented in the PyEMMA
software - http://pyemma.org - as of version 2.0
IRD dropout study
This final report describes work performed by SRS Technologies for the NASA Marshall Space Flight Center under Contract NAS8-39077, entitled 'Integrated Receiver-Decoder Dropout Study'. The purpose of the study was to determine causes of signal fading effects on ultra-high-frequency (UHF) range safety transmissions to the Space Shuttle during flyout. Of particular interest were deep fades observed at the External Tank (ET) Integrated Receiver-Decoder (IRD) during the flyout interval between solid rocket booster separation and ET separation. Analytical and simulation methods were employed in this study to assess observations captured in flight telemetry data records. Conclusions based on the study are presented in this report, and recommendations are given for future experimental validation of the results
Automatic programming of simulation models
The concepts of software engineering were used to improve the simulation modeling environment. Emphasis was placed on the application of an element of rapid prototyping, or automatic programming, to assist the modeler define the problem specification. Then, once the problem specification has been defined, an automatic code generator is used to write the simulation code. The following two domains were selected for evaluating the concepts of software engineering for discrete event simulation: manufacturing domain and a spacecraft countdown network sequence. The specific tasks were to: (1) define the software requirements for a graphical user interface to the Automatic Manufacturing Programming System (AMPS) system; (2) develop a graphical user interface for AMPS; and (3) compare the AMPS graphical interface with the AMPS interactive user interface
Automatic programming of simulation models
The objective of automatic programming is to improve the overall environment for describing the program. This improved environment is realized by a reduction in the amount of detail that the programmer needs to know and is exposed to. Furthermore, this improved environment is achieved by a specification language that is more natural to the user's problem domain and to the user's way of thinking and looking at the problem. The goal of this research is to apply the concepts of automatic programming (AP) to modeling discrete event simulation system. Specific emphasis is on the design and development of simulation tools to assist the modeler define or construct a model of the system and to then automatically write the corresponding simulation code in the target simulation language, GPSS/PC. A related goal is to evaluate the feasibility of various languages for constructing automatic programming simulation tools
The paradigm of the area law and the structure of transversal and longitudinal lightfront degrees of freedom
It is shown that an algebraically defined holographic projection of a QFT
onto the lightfront changes the local quantum properties in a very drastic way.
The expected ubiquitous vacuum polarization characteristic of QFT is confined
to the lightray (longitudinal) direction, whereas operators whose localization
is transversely separated are completely free of vacuum correlations. This
unexpected ''transverse return to QM'' combined with the rather universal
nature of the strongly longitudinal correlated vacuum correlations (which turn
out to be described by rather kinematical chiral theories) leads to a d-2
dimensional area structure of the d-1 dimensional lightfront theory. An
additive transcription in terms of an appropriately defined entropy related to
the vacuum restricted to the horizon is proposed and its model independent
universality aspects which permit its interpretation as a quantum candidate for
Bekenstein's area law are discussed. The transverse tensor product foliation
structure of lightfront degrees of freedom is essential for the simplifying
aspects of the algebraic lightcone holography. Key-words: Quantum field theory;
Mathematical physics, Quantum gravityComment: 16 pages latex, identical to version published in JPA: Math. Gen. 35
(2002) 9165-918
- …