44 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
Cosmological horizons and reconstruction of quantum field theories
As a starting point, we state some relevant geometrical properties enjoyed by
the cosmological horizon of a certain class of Friedmann-Robertson-Walker
backgrounds. Those properties are generalised to a larger class of expanding
spacetimes admitting a geodesically complete cosmological horizon \scrim
common to all co-moving observers. This structure is later exploited in order
to recast, in a cosmological background, some recent results for a linear
scalar quantum field theory in spacetimes asymptotically flat at null infinity.
Under suitable hypotheses on , encompassing both the cosmological de Sitter
background and a large class of other FRW spacetimes, the algebra of
observables for a Klein-Gordon field is mapped into a subalgebra of the algebra
of observables \cW(\scrim) constructed on the cosmological horizon. There is
exactly one pure quasifree state on \cW(\scrim) which fulfils a
suitable energy-positivity condition with respect to a generator related with
the cosmological time displacements. Furthermore induces a preferred
physically meaningful quantum state for the quantum theory in the
bulk. If admits a timelike Killing generator preserving \scrim, then the
associated self-adjoint generator in the GNS representation of has
positive spectrum (i.e. energy). Moreover turns out to be invariant
under every symmetry of the bulk metric which preserves the cosmological
horizon. In the case of an expanding de Sitter spacetime, coincides
with the Euclidean (Bunch-Davies) vacuum state, hence being Hadamard in this
case. Remarks on the validity of the Hadamard property for in more
general spacetimes are presented.Comment: 32 pages, 1 figure, to appear on Comm. Math. Phys., dedicated to
Professor Klaus Fredenhagen on the occasion of his 60th birthda
Lorentz-invariant CPT violation
A Lorentz-invariant CPT violation, which may be termed as long-distance CPT
violation in contrast to the familiar short-distance CPT violation, has been
recently proposed. This scheme is based on a non-local interaction vertex and
characterized by an infrared divergent form factor. We show that the Lorentz
covariant -product is consistently defined and the energy-momentum
conservation is preserved in perturbation theory if the path integral is
suitably defined for this non-local theory, although unitarity is generally
lost. It is illustrated that T violation is realized in the decay and formation
processes. It is also argued that the equality of masses and decay widths of
the particle and anti-particle is preserved if the non-local CPT violation is
incorporated either directly or as perturbation by starting with the
conventional CPT-even local Lagrangian. However, we also explicitly show that
the present non-local scheme can induce the splitting of particle and
anti-particle mass eigenvalues if one considers a more general class of
Lagrangians.Comment: 28 pages; note added in proof; version published in Eur. Phys. J. C
(2013) 73: 234
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
2003 AAPP Monograph Series
It is significant that the African American Professors Program (AAPP) at the University of South Carolina is producing the third edition of its annual monograph series at this time-the fifth anniversary of AAPP. The program graciously accepts the challenge of putting into place a requirement for the scholars to produce quality research papers worthy of publication. This provides widespread visibility for them and enhances their curriculum vitae concurrently.
Scholars who have contributed manuscripts for this monograph are to be commended for adding this additional responsibility to their academic workload. Writing across disciplines adds to the intellectual diversity of these papers. From neophytes, relatively speaking, to an array of very experienced individuals, the chapters have been researched and comprehensively written.
Founded in 1997 through the Department of Educational Leadership and Policies in the College of Education, AAPP was designed to address the underrepresentation of African American professors on college and university campuses. Its mission is to expand the pool of these professors in critical academic and research areas. Sponsored by the University of South Carolina, the W. K. Kellogg Foundation, and the South Carolina General Assembly, the program recruits students with bachelor\u27s, master\u27s, and doctoral degrees for disciplines in which African Americans currently are underrepresented.
An important component of the program is the mentoring experience that is provided. Each student is assigned to a mentor/professor who guides the student through a selected academic program and provides various learning experiences. When possible, the mentor serves as chair of the student\u27s doctoral committee. The mentor also provides opportunities for the student to team teach, conduct research, and co-author publications. Students have the advantage of attending committee, faculty, and professional meetings, as well as engaging in a range of activities that characterize professional life in academia. Scholars enrolled in the program also are involved in programmatic and institutional workshops, independent research, and program development.
The continuation of this monograph series is seen as responding to a window of opportunity to be sensitive to an academic expectation of graduates as they pursue career placement and, at the same time, one that allows for the dissemination of AAPP products to a broader community. The importance of this monograph series has been voiced by one of our 2002 AAPP graduates, Dr. Shundelle LaTjuan Dogan, a recent Harvard Administrative Fellow at Harvard University and now Program Officer for the Southern Education Foundation, Atlanta, Georgia. Dr. Dogan wrote: One thing in particular that I want to thank you for is having the African American Professors Program scholars publish articles for the monograph. I have to admit that writing the articles seemed like extra work at the time. However, in my recent interview process, organizations have asked me for samples of my writing. Including an article from a published monograph helped to make my portfolio much more impressive. You were right on target in having us do the monograph series.
We hope that you will read this monograph of the African American Professors Program with enthusiasm or enlightenment.
John McFadden, Ph.D.
The Benjamin Elijah Mays Professor
Director, African American Professors Program
University of South Carolinahttps://scholarcommons.sc.edu/mcfadden_monographs/1006/thumbnail.jp
2002 AAPP Monograph Series: African American Professors Program
The African American Professors Program (AAPP) at the University of South Carolina is pleased to produce the second edition of its annual monograph series. It is fitting that the program contrives to assume a leadership role in promoting scholarly products that prove to be useful in research endeavors by faculty and students in higher education.
Scholars who have contributed manuscripts for this monograph are to be commended for adding this additional responsibility to their academic workload. Writing across disciplines adds to the intellectual diversity of these papers. From neophytes, relatively speaking, to an array of very experienced individuals, the chapters have been researched and comprehensively written.
Founded in 1997 through the Department of Educational Leadership and Policies in the College of Education, AAPP was designed to address the underrepresentation of African American professors on college and university campuses. Its mission is to expand the pool of these professors in critical academic and research areas. Sponsored by the University of South Carolina, the W.K. Kellogg Foundation, and the South Carolina General Assembly, the program recruits students with bachelor\u27s, master\u27s, and doctoral degrees for disciplines in which African Americans, currently, are underrepresented.
An important component of the program is the mentoring experience that is provided. Each student is assigned to a mentor professor who guides the student through a selected academic program and provides various learning experiences. When possible, the mentor serves as chair of the student\u27s doctoral committee. The mentor, also, provides opportunities for the student to team teach, conduct research, and co-author publications. Students have opportunities to attend committee, faculty, and professional meetings, as well as to engage in a range of activities that characterize professional life in academia. Scholars enrolled in the program also are involved in programmatic and institutional workshops, independent research, and program development.
The continuation of this monograph series is seen as responding to an opportunity to be sensitive to an academic expectation of graduates as they pursue career placement and, also, one that allows for the dissemination of AAPP products to a broader community. We hope that you will read this monograph of the African American Professors Program with enthusiasm or enlightenment.
John McFadden, Ph.D.
The Benjamin Elijah Mays Professor
Director, African American Professors Program
University of South Carolinahttps://scholarcommons.sc.edu/mcfadden_monographs/1000/thumbnail.jp
An alternative to the gauge theoretic setting
The standard formulation of gauge theories results from the Lagrangian
(functional integral) quantization of classical gauge theories. A more
intrinsic qunantum theoretical access in the spirit of Wigner's representation
theory shows that there is a fundamental clash between the pointlike
localization of zero mass (vector, tensor) potentials and the Hilbert space
(positivity, unitarity) structure of QT. The quantization approach has no other
way than to stay with pointlike localization and sacrifice the Hilbert space
whereas the approach build on the intrinsic quantum concept of modular
localization keeps the Hilbert space and trades the conflict creating pointlike
generation with the tightest consistent localization:: semiinfinite spacelike
string localization. Whereas these potentials in the presence of interactions
stay quite close to associated pointlike field strength, the interacting matter
fields to which they are coupled bear the brunt of the nonlocal aspect in that
they are string.generated in a way which cannot be undone by any
differentiation. The new stringlike approach to gauge theory also revives the
idea of a Schwinger-Higgs screening mechanism as a deeper and less metaphoric
description of the Higgs spontaneous symmetry breaking and its accompanying
tale about "God's particle" and its mass generation for all other particles.Comment: 26 page
A critical look at 50 years particle theory from the perspective of the crossing property
The crossing property is perhaps the most subtle aspect of the particle-field
relation. Although it is not difficult to state its content in terms of certain
analytic properties relating different matrixelements of the S-matrix or
formfactors, its relation to the localization- and positive energy spectral
principles requires a level of insight into the inner workings of QFT which
goes beyond anything which can be found in typical textbooks on QFT. This paper
presents a recent account based on new ideas derived from "modular
localization" including a mathematic appendix on this subject. Its main novel
achievement is the proof of the crossing property of formfactors from a
two-algebra generalization of the KMS condition. The main content of this
article is the presentation of the derailments of particle theory during more
than 4 decades: the S-matrix bootstrap, the dual model and its string theoretic
extension. Rather than being related to crossing, string theory is the (only
known) realization of a dynamic infinite component one-particle wave function
space and its associated infinite component field. Here "dynamic" means that,
unlike a mere collection of infinitely many irreducible unitary Poincar\'e
group representation or free fields, the formalism contains also operators
which communicate between the different irreducible Poincar\'e represenations
(the levels of the "infinite tower") and set the mass/spin spectrum. Wheras in
pre-string times there were unsuccessful attempts to achieve this in analogy to
the O(4,2) hydrogen spectrum by the use of higher noncompact groups, the
superstring in d=9+1, which uses instead (bosonic/fermionic) oscillators
obtained from multicomponent chiral currents is the only known unitary positive
energy solution of the dynamical infinite component pointlike localized field
project.Comment: 66 pages, addition of new results, addition of references, will
appear in this form in Foundations of Physic
Recommended from our members
A full year of aerosol size distribution data from the central Arctic under an extreme positive Arctic Oscillation : insights from the Multidisciplinarydrifting Observatory for the Study of Arctic Climate (MOSAiC) expedition
The Arctic environment is rapidly changing due to accelerated warming in the region. The warming trend is driving a decline in sea ice extent, which thereby enhances feedback loops in the surface energy budget in the Arctic. Arctic aerosols play an important role in the radiative balance and hence the climate response in the region, yet direct observations of aerosols over the Arctic Ocean are limited. In this study, we investigate the annual cycle in the aerosol particle number size distribution (PNSD), particle number concentration (PNC), and black carbon (BC) mass concentration in the central Arctic during the Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition. This is the first continuous, year-long data set of aerosol PNSD ever collected over the sea ice in the central Arctic Ocean. We use a k-means cluster analysis, FLEXPART simulations, and inverse modeling to evaluate seasonal patterns and the influence of different source regions on the Arctic aerosol population. Furthermore, we compare the aerosol observations to land-based sites across the Arctic, using both long-term measurements and observations during the year of the MOSAiC expedition (2019-2020), to investigate interannual variability and to give context to the aerosol characteristics from within the central Arctic. Our analysis identifies that, overall, the central Arctic exhibits typical seasonal patterns of aerosols, including anthropogenic influence from Arctic haze in winter and secondary aerosol processes in summer. The seasonal pattern corresponds to the global radiation, surface air temperature, and timing of sea ice melting/freezing, which drive changes in transport patterns and secondary aerosol processes. In winter, the Norilsk region in Russia/Siberia was the dominant source of Arctic haze signals in the PNSD and BC observations, which contributed to higher accumulation-mode PNC and BC mass concentrations in the central Arctic than at land-based observatories. We also show that the wintertime Arctic Oscillation (AO) phenomenon, which was reported to achieve a record-breaking positive phase during January-March 2020, explains the unusual timing and magnitude of Arctic haze across the Arctic region compared to longer-term observations. In summer, the aerosol PNCs of the nucleation and Aitken modes are enhanced; however, concentrations were notably lower in the central Arctic over the ice pack than at land-based sites further south. The analysis presented herein provides a current snapshot of Arctic aerosol processes in an environment that is characterized by rapid changes, which will be crucial for improving climate model predictions, understanding linkages between different environmental processes, and investigating the impacts of climate change in future Arctic aerosol studies.Peer reviewe
Substantial contribution of iodine to Arctic ozone destruction
Unlike bromine, the effect of iodine chemistry on the Arctic surface ozone budget is poorly constrained. We present ship-based measurements of halogen oxides in the high Arctic boundary layer from the sunlit period of March to October 2020 and show that iodine enhances springtime tropospheric ozone depletion. We find that chemical reactions between iodine and ozone are the second highest contributor to ozone loss over the study period, after ozone photolysis-initiated loss and ahead of bromine.Iodine chemistry plays a more important role than bromine chemistry in tropospheric ozone losses in the Arctic, according to ship-based observations of halogen oxides from March to October 2020.Peer reviewe