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B. Schroer

Publications and source records attributed to B. Schroer.

12 recordsLinked to original sources
arXiv2023

The saturation of the Bell instability and its implications for cosmic ray acceleration and transport

The non-resonant (Bell) streaming instability driven by energetic particles is crucial for producing amplified magnetic fields that are key to the acceleration of cosmic rays (CRs) in supernova remnants, around Galactic and extra-galactic CR sources, and for the CR transport. We present a covariant theory for the saturation of the Bell instability, substantiated by self-consistent kinetic simulations, that can be applied to arbitrary CR distributions and discuss its implications in several heliospheric and astrophysical contexts.

astro-ph.HE↗
arXiv2005

String-localized Quantum Fields and Modular Localization

We study free, covariant, quantum (Bose) fields that are associated with irreducible representations of the Poincaré group and localized in semi-infinite strings extending to spacelike infinity. Among these are fields that generate the irreducible representations of mass zero and infinite spin that are known to be incompatible with point-like localized fields. For the massive representation and the massless representations of finite helicity, all string-localized free fields can be written as an integral, along the string, of point-localized tensor or spinor fields. As a special case we discuss the string-localized vector fields associated with the point-like electromagnetic field and their relation to the axial gauge condition in the usual setting.

math-ph↗
arXiv1999

Looking beyond the Thermal Horizon: Hidden Symmetries in Chiral Models

In thermal states of chiral theories, as recently investigated by H.-J. Borchers and J. Yngvason, there exists a rich group of hidden symmetries. Here we show that this leads to a radical converse of of the Hawking-Unruh observation in the following sense. The algebraic commutant of the algebra associated with a (heat bath) thermal chiral system can be used to reprocess the thermal system into a ground state system on a larger algebra with a larger localization space-time. This happens in such a way that the original system appears as a kind of generalized Unruh restriction of the ground state sytem and the thermal commutant as being transmutated into newly created ``virgin space-time region'' behind a horizon. The related concepts of a ``chiral conformal core'' and the possibility of a ``blow-up'' of the latter suggest interesting ideas on localization of degrees of freedom with possible repercussion on how to define quantum entropy of localized matter content in Local Quantum Physics.

hep-th↗
arXiv1999

Modular Constructions of Quantum Field Theories with Interactions

We extend the previously introduced constructive modular method to nonperturbative QFT. In particular the relevance of the concept of ``quantum localization'' (via intersection of algebras) versus classical locality (via support properties of test functions) is explained in detail, the wedge algebras are constructed rigorously and the formal aspects of double cone algebras for d=1+1 factorizing theories are determined. The well-known on-shell crossing symmetry of the S-Matrix and of formfactors (cyclicity relation) in such theories is intimately related to the KMS properties of new quantum-local PFG (one-particle polarization-free generators) of these wedge algebras. These generators are ``on-shell'' and their Fourier transforms turn out to fulfill the Zamolodchikov-Faddeev algebra. As the wedge algebras contain the crossing symmetry informations, the double cone algebras reveal the particle content of fields. Modular theory associates with this double cone algebra two very useful chiral conformal quantum field theories which are the algebraic versions of the light ray algebras.

hep-th↗
arXiv1998

Modular Theory and Geometry

In this letter we present some new results on modular theory and its application in quantum field theory. In doing this we develop some new proposals how to generalize concepts of geometrical action. Therefore the spirit of this letter is more on a programmatic side with many details remaining to be elaborated.

math-ph↗
arXiv1998

Localization and Nonperturbative Local Quantum Physics

The main content of this treatise is a new concept in nonperturbative non-Lagrangian QFT which explains and extends the ad hoc constructions in low-dimensional models and incorporates them together with the higher dimensional theories into a new construction method. Thermal and entropical properties, which were hitherto restricted to situations with classical horizons (Killing vectors), are now generic (nonperturbative) aspects of "modular localization". The underlying more algebraic (and less geometric) mode of thinking also gives rise to interesting questions in renormalizable deformatioms of higher spin fields, in particular gauge theories.

hep-th↗
arXiv1997

Wigner Representation Theory of the Poincare Group, Localization, Statistics and the S-Matrix

It has been known that the Wigner representation theory for positive energy orbits permits a useful localization concept in terms of certain lattices of real subspaces of the complex Hilbert -space. This ''modular localization'' is not only useful in order to construct interaction-free nets of local algebras without using non-unique ''free field coordinates'', but also permits the study of properties of localization and braid-group statistics in low-dimensional QFT. It also sheds some light on the string-like localization properties of the 1939 Wigner's ''continuous spin'' representations.We formulate a constructive nonperturbative program to introduce interactions into such an approach based on the Tomita-Takesaki modular theory. The new aspect is the deep relation of the latter with the scattering operator.

hep-th↗
arXiv1996

Motivations and Physical Aims of Algebraic QFT

We present illustrations which show the usefulness of algebraic QFT. In particular in low-dimensional QFT, when Lagrangian quantization does not exist or is useless (e.g. in chiral conformal theories), the algebraic method is beginning to reveal its strength.

hep-th↗
arXiv1994

Reminiscences about Many Pitfalls and Some Successes of QFT Within the Last Three Decades

Laymen and sometimes even physicists think of natural sciences, in particular of theoretical and mathematical physics often as subjects, which unfold according to an intrinsic logical pattern, with the limitations being set only by the conceptual and (in case of mathematical physics) mathematical developments of the times. This view certainly cannot be maintained in view of the present stagnation and crisis which in particular affects QFT, an area which in the past has been most innovating and fruitful, also in relation to other important areas of theoretical physics.

hep-th↗
arXiv1994

Some Useful Properties of Rotational Gibbs States In Chiral Conformal QFT

We derive the Kac Wakimoto formula in the algebraic framework of chiral conformal QFT s a consequence of the universal behaviour of high-temperature Gibbs-states on intertwiner subalgebras. By studying selfintertwiners in the presence of other charges, we obtain charge-polarization coefficients which generalize the entries of Verlinde matrix S and belong to higher genus mapping class group matrices.

hep-th↗
arXiv1993

Modular Theory and Symmetry in QFT

The application of the Tomita-Takesaki modular theory to the Haag-Kastler net approach in QFT yields external (space-time) symmetries as well as internal ones (internal ``gauge para-groups") and their dual counterparts (the ``super selection para-group"). An attempt is made to develop a (speculative) picture on ``quantum symmetry" which links space-time symmetries in an inexorable way with internal symmetries. In the course of this attempt, we present several theorems and in particular derive the Kac-Wakimoto formula which links Jones inclusion indices with the asymptotics of expectation values in physical temperature states. This formula is a special case of a new asymptotic Gibbs-state representation of mapping class group matrices (in a Haag-Kastler net indexed by intervals on the circle!) as well as braid group matrices.

hep-th↗