46 research outputs found
A sharpened nuclearity condition for massless fields
A recently proposed phase space condition which comprises information about
the vacuum structure and timelike asymptotic behavior of physical states is
verified in massless free field theory. There follow interesting conclusions
about the momentum transfer of local operators in this model.Comment: 13 pages, LaTeX. As appeared in Letters in Mathematical Physic
Asymptotic completeness in a class of massless relativistic quantum field theories
This paper presents the first examples of massless relativistic quantum field
theories which are interacting and asymptotically complete. These
two-dimensional theories are obtained by an application of a deformation
procedure, introduced recently by Grosse and Lechner, to chiral conformal
quantum field theories. The resulting models may not be strictly local, but
they contain observables localized in spacelike wedges. It is shown that the
scattering theory for waves in two dimensions, due to Buchholz, is still valid
under these weaker assumptions. The concepts of interaction and asymptotic
completeness, provided by this theory, are adopted in the present
investigation.Comment: 15 pages, LaTeX. As appeared in Communications in Mathematical
Physic
Towards a construction of inclusive collision cross-sections in the massless Nelson model
The conventional approach to the infrared problem in perturbative quantum
electrodynamics relies on the concept of inclusive collision cross-sections. A
non-perturbative variant of this notion was introduced in algebraic quantum
field theory. Relying on these insights, we take first steps towards a
non-perturbative construction of inclusive collision cross-sections in the
massless Nelson model. We show that our proposal is consistent with the
standard scattering theory in the absence of the infrared problem and discuss
its status in the infrared-singular case.Comment: 23 pages, LaTeX. As appeared in Ann. Henri Poincar\'
Continuous Spectrum of Automorphism Groups and the Infraparticle Problem
This paper presents a general framework for a refined spectral analysis of a
group of isometries acting on a Banach space, which extends the spectral theory
of Arveson. The concept of continuous Arveson spectrum is introduced and the
corresponding spectral subspace is defined. The absolutely continuous and
singular-continuous parts of this spectrum are specified. Conditions are given,
in terms of the transposed action of the group of isometries, which guarantee
that the pure-point and continuous subspaces span the entire Banach space. In
the case of a unitarily implemented group of automorphisms, acting on a
-algebra, relations between the continuous spectrum of the automorphisms
and the spectrum of the implementing group of unitaries are found. The group of
spacetime translation automorphisms in quantum field theory is analyzed in
detail. In particular, it is shown that the structure of its continuous
spectrum is relevant to the problem of existence of (infra-)particles in a
given theory.Comment: 31 pages, LaTeX. As appeared in Communications in Mathematical
Physic
Superselection Sectors and General Covariance.I
This paper is devoted to the analysis of charged superselection sectors in
the framework of the locally covariant quantum field theories. We shall analize
sharply localizable charges, and use net-cohomology of J.E. Roberts as a main
tool. We show that to any 4-dimensional globally hyperbolic spacetime it is
attached a unique, up to equivalence, symmetric tensor \Crm^*-category with
conjugates (in case of finite statistics); to any embedding between different
spacetimes, the corresponding categories can be embedded, contravariantly, in
such a way that all the charged quantum numbers of sectors are preserved. This
entails that to any spacetime is associated a unique gauge group, up to
isomorphisms, and that to any embedding between two spacetimes there
corresponds a group morphism between the related gauge groups. This form of
covariance between sectors also brings to light the issue whether local and
global sectors are the same. We conjecture this holds that at least on simply
connected spacetimes. It is argued that the possible failure might be related
to the presence of topological charges. Our analysis seems to describe theories
which have a well defined short-distance asymptotic behaviour.Comment: 66 page
Asymptotic completeness for infraparticles in two-dimensional conformal field theory
We formulate a new concept of asymptotic completeness for two-dimensional
massless quantum field theories in the spirit of the theory of particle
weights. We show that this concept is more general than the standard particle
interpretation based on Buchholz' scattering theory of waves. In particular, it
holds in any chiral conformal field theory in an irreducible product
representation and in any completely rational conformal field theory. This
class contains theories of infraparticles to which the scattering theory of
waves does not apply.Comment: 17 pages, no figur
Infraparticles with superselected direction of motion in two-dimensional conformal field theory
Particle aspects of two-dimensional conformal field theories are
investigated, using methods from algebraic quantum field theory. The results
include asymptotic completeness in terms of (counterparts of) Wigner particles
in any vacuum representation and the existence of (counterparts of)
infraparticles in any charged irreducible product representation of a given
chiral conformal field theory. Moreover, an interesting interplay between the
infraparticle's direction of motion and the superselection structure is
demonstrated in a large class of examples. This phenomenon resembles the
electron's momentum superselection expected in quantum electrodynamics.Comment: 34 pages, no figure. The final version is available under Open
Access. CC-B
Parity nonconservation effects in the photodesintegration of polarized deuterons
P-odd correlations in the deuteron photodesintegration are considered. The
-meson exchange is not operative in the case of unpolarized deuterons. For
polarized deuterons a P-odd correlation due to the -meson exchange is
about . Short-distance P-odd contributions exceed essentially
than the contribution of the -meson exchange.Comment: 12 pages, Latex, 3 figure
Noninteraction of waves in two-dimensional conformal field theory
In higher dimensional quantum field theory, irreducible representations of
the Poincare group are associated with particles. Their counterpart in
two-dimensional massless models are "waves" introduced by Buchholz. In this
paper we show that waves do not interact in two-dimensional Moebius covariant
theories and in- and out-asymptotic fields coincide. We identify the set of the
collision states of waves with the subspace generated by the chiral components
of the Moebius covariant net from the vacuum. It is also shown that
Bisognano-Wichmann property, dilation covariance and asymptotic completeness
(with respect to waves) imply Moebius symmetry.
Under natural assumptions, we observe that the maps which give asymptotic
fields in Poincare covariant theory are conditional expectations between
appropriate algebras. We show that a two-dimensional massless theory is
asymptotically complete and noninteracting if and only if it is a chiral
Moebius covariant theory.Comment: 28 pages, no figur
Broadening the phenotypic and molecular spectrum of FINCA syndrome: Biallelic NHLRC2 variants in 15 novel individuals
FINCA syndrome [MIM: 618278] is an autosomal recessive multisystem disorder characterized by fibrosis, neurodegeneration and cerebral angiomatosis. To date, 13 patients from nine families with biallelic NHLRC2 variants have been published. In all of them, the recurrent missense variant p.(Asp148Tyr) was detected on at least one allele. Common manifestations included lung or muscle fibrosis, respiratory distress, developmental delay, neuromuscular symptoms and seizures often followed by early death due to rapid disease progression.Here, we present 15 individuals from 12 families with an overlapping phenotype associated with nine novel NHLRC2 variants identified by exome analysis. All patients described here presented with moderate to severe global developmental delay and variable disease progression. Seizures, truncal hypotonia and movement disorders were frequently observed. Notably, we also present the first eight cases in which the recurrent p.(Asp148Tyr) variant was not detected in either homozygous or compound heterozygous state.We cloned and expressed all novel and most previously published non-truncating variants in HEK293-cells. From the results of these functional studies, we propose a potential genotype-phenotype correlation, with a greater reduction in protein expression being associated with a more severe phenotype.Taken together, our findings broaden the known phenotypic and molecular spectrum and emphasize that NHLRC2-related disease should be considered in patients presenting with intellectual disability, movement disorders, neuroregression and epilepsy with or without pulmonary involvement