536 research outputs found
Distribution of satellite galaxies in high redshift groups
We use galaxy groups at redshifts between 0.4 and 1.0 selected from the Great
Observatories Origins Deep Survey (GOODS) to study the color-morphological
properties of satellite galaxies, and investigate possible alignment between
the distribution of the satellites and the orientation of their central galaxy.
We confirm the bimodal color and morphological type distribution for satellite
galaxies at this redshift range: the red and blue classes corresponds to the
early and late morphological types respectively, and the early-type satellites
are on average brighter than the late-type ones. Furthermore, there is a {\it
morphological conformity} between the central and satellite galaxies: the
fraction of early-type satellites in groups with an early-type central is
higher than those with a late-type central galaxy. This effect is stronger at
smaller separations from the central galaxy. We find a marginally significant
signal of alignment between the major axis of the early-type central galaxy and
its satellite system, while for the late-type centrals no significant alignment
signal is found. We discuss the alignment signal in the context of shape
evolution of groups.Comment: 7 pages, 7 figures, accepted by Ap
Presentations of Wess-Zumino-Witten Fusion Rings
The fusion rings of Wess-Zumino-Witten models are re-examined. Attention is
drawn to the difference between fusion rings over Z (which are often of greater
importance in applications) and fusion algebras over C. Complete proofs are
given characterising the fusion algebras (over C) of the SU(r+1) and Sp(2r)
models in terms of the fusion potentials, and it is shown that the analagous
potentials cannot describe the fusion algebras of the other models. This
explains why no other representation-theoretic fusion potentials have been
found.
Instead, explicit generators are then constructed for general WZW fusion
rings (over Z). The Jacobi-Trudy identity and its Sp(2r) analogue are used to
derive the known fusion potentials. This formalism is then extended to the WZW
models over the spin groups of odd rank, and explicit presentations of the
corresponding fusion rings are given. The analogues of the Jacobi-Trudy
identity for the spinor representations (for all ranks) are derived for this
purpose, and may be of independent interest.Comment: 32 pages, 3 figures, added references, minor additions to text. To be
published in Rev. Math. Phy
On the Cohomology of the Noncritical -string
We investigate the cohomology structure of a general noncritical
-string. We do this by introducing a new basis in the Hilbert space in
which the BRST operator splits into a ``nested'' sum of nilpotent BRST
operators. We give explicit details for the case . In that case the BRST
operator can be written as the sum of two, mutually anticommuting,
nilpotent BRST operators: . We argue that if one chooses for the
Liouville sector a minimal model then the cohomology of the
operator is closely related to a Virasoro minimal model. In particular,
the special case of a (4,3) unitary minimal model with central charge
leads to a Ising model in the cohomology. Despite all this,
noncritical strings are not identical to noncritical Virasoro strings.Comment: 38 pages, UG-7/93, ITP-SB-93-7
The BV-algebra structure of W_3 cohomology
We summarize some recent results obtained in collaboration with J. McCarthy
on the spectrum of physical states in gravity coupled to matter. We
show that the space of physical states, defined as a semi-infinite (or BRST)
cohomology of the algebra, carries the structure of a BV-algebra. This
BV-algebra has a quotient which is isomorphic to the BV-algebra of polyvector
fields on the base affine space of . Details have appeared elsewhere.
[Published in the proceedings of "Gursey Memorial Conference I: Strings and
Symmetries," Istanbul, June 1994, eds. G. Aktas et al., Lect. Notes in Phys.
447, (Springer Verlag, Berlin, 1995)]Comment: 8 pages; uses macros tables.tex and amssym.def (version 2.1 or later
Hepatitis E virus infections in pigs : transmission dynamics and human exposure
In dit promotieonderzoek is de transmissie dynamiek van Hepatitis E virus (HEV) bij varkens onderzocht, alsmede de potentiële blootstelling van de Nederlandse bevolking aan HEV uit varkens. Om te onderzoeken of HEV spreidt onder varkens is een experiment opgezet bestaande uit 10 infectieketens. Elke keten bestond uit één intraveneus geïnfecteerd varken ( iv‐varkens) en drie HEV‐gevoelige varkens (contactvarkens). Aan elk van de 10 iv‐varkens is een HEV‐naïef varken blootgesteld (één‐op‐één blootstelling). Indien dit naïeve varken werd geïnfecteerd, werd een volgend HEV‐naïef varken uit de keten aan het zojuist geïnfecteerde varken blootgesteld
Semi-infinite cohomology of W-algebras
We generalize some of the standard homological techniques to \cW-algebras,
and compute the semi-infinite cohomology of the \cW_3 algebra on a variety of
modules. These computations provide physical states in \cW_3 gravity coupled
to \cW_3 minimal models and to two free scalar fields.Comment: 15 page
Local Operators in Massive Quantum Field Theories
Contribution to the proceedings of Schladming 1995. A review of the form
factor approach and its utilisation to determine the space of local operators
of integrable massive quantum theories is given. A few applications are
discussed.Comment: 6 pages, late
On the Topology and Flux of T-Dual Manifolds
We present a general formula for the topology and H-flux of the T-dual of a
type two compactification. Our results apply to T-dualities with respect to any
free circle action. In particular we find that the manifolds on each side of
the duality are circle bundles whose curvatures are given by the integral of
the dual H-flux over the dual circle. As a corollary we conjecture an
obstruction to multiple T-dualities, generalizing an obstruction known to exist
on the twisted torus. Examples include SU(2) WZW models, Lens spaces and the
supersymmetric string theory on the non-spin AdS^5xCP^2xS^1 compactification.Comment: 4 Pages, No Figure
Twisted K-theory and K-theory of bundle gerbes
In this note we introduce the notion of bundle gerbe K-theory and investigate
the relation to twisted K-theory. We provide some examples. Possible
applications of bundle gerbe K-theory to the classification of D-brane charges
in non-trivial backgrounds are discussed.Comment: 29 pages, corrected typos, added references, included new section on
twisted Chern character in non-torsion cas
Fock space resolutions of the Virasoro highest weight modules with c<=1
We extend Felder's construction of Fock space resolutions for the Virasoro
minimal models to all irreducible modules with . In particular, we
provide resolutions for the representations corresponding to the boundary and
exterior of the Kac table.Comment: 14 pages, revised versio
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