150 research outputs found
Exact Bosonic and Supersymmetric String Black Hole Solutions
We show that Witten's two-dimensional string black hole metric is exactly
conformally invariant in the supersymmetric case. We also demonstrate that this
metric, together with a recently proposed exact metric for the bosonic case,
are respectively consistent with the supersymmetric and bosonic -model
conformal invariance conditions up to four-loop order.Comment: 14
A Measurement of the Low Mass Drell-Yan Di fferential Cross Section in the Di-Muon Channel with Âș s = 7 TeV Proton-Proton Collisions at the ATLAS Experiment
PhDA measurement of the Drell-Yan di fferential cross section at low invariant mass is presented
in the di-muon channel. A 1.64 pbâ1 dataset of
Âș
s = 7 TeV proton-proton collision
data collected by the ATLAS experiment at the LHC is used. The measurement is made
in an invariant mass range of 26 < M < 66 GeV where M is the invariant mass of
the muon pair. A review of the relevant theoretical physics and the ATLAS detector is made. The analysis is described with particular attention paid to the determination of the isolation e fficiency corrections for the Monte Carlo and the estimate of the multijet background.
The fiducial diff erential cross section is calculated with a statistical uncertainty
that varies between 0.8% and 1.2%. The systematic uncertainty is seen to vary between 2.4% and 4.1%. A cross section extrapolated to the full phase space is also presented.
This is dominated by theoretical uncertainties from the variation of the factorisation and renormalisation scales. The obtained fi ducial diff erential mass cross section is compared to
theoretical predictions at NLO and NNLO in perturbative QCD. It is shown that a move
beyond NLO is needed to describe the distribution well due to the restrictions of using a fixed order theoretical prediction. A combination with the electron channel measurement
is also briefly discussed as well as comparisons to a di-muon measurement in an extended invariant mass range. This allows similar, but stronger conclusions to be drawn. A discussion is made of a PDF fit that uses the measurement presented here. The fi t demonstrates the impact of the measurement on the PDFs and further supports the conclusion that a move to NNLO in pQCD is needed to describe the data.STF
The geometry of supersymmetric coset models and superconformal algebras
An on-shell formulation of (p,q), 2\leq p \leq 4, 0\leq q\leq 4,
supersymmetric coset models with target space the group G and gauge group a
subgroup H of G is given. It is shown that there is a correspondence between
the number of supersymmetries of a coset model and the geometry of the coset
space G/H. The algebras of currents of supersymmetric coset models are
superconformal algebras. In particular, the algebras of currents of (2,2) and
(4,0) supersymmetric coset models are related to the N=2 Kazama-Suzuki and N=4
Van Proeyen superconformal algebras correspondingly.Comment: pages 2
Chiral gauged WZNW models and heterotic string backgrounds
We construct new heterotic string backgrounds which are analogous to
superstring solutions corresponding to coset models but are not simply the
`embeddings'of the latter. They are described by the (1,0) supersymmetric
extension of the chiral gauged WZNW models. The `chiral gauged' WZNW
action differs from the standard gauged WZNW action by the absence of the
-term (and thus is not gauge invariant in the usual sense) but can
still be expressed as a combination of WZNW actions and is conformal invariant.
We explain a close relation between gauged and chiral gauged WZNW models and
prove that in the case of the abelian the chiral gauged theory is
equivalent to a particular gauged WZNW theory. In contrast to
the gauged WZNW model, the chiral gauged one admits a (1,0) supersymmetric
extension which is consistent at the quantum level. Integrating out the
gauge field we determine the exact (in ) form of the couplings of the
corresponding heterotic sigma model. While in the bosonic (superstring) cases
all the fields depend (do not depend) non-trivially on here the
metric receives only one correction while the antisymmetric tensor
and the dilaton remain semiclassical. As a simplest example, we discuss the
basic solution which is the heterotic string counterpart of the `black
string' background.Comment: 41 pages, harvmac, CERN-TH.6962, USC-93/HEP-S
Gauging a Non-Semi-Simple WZW Model
We consider gauged WZW models based on a four dimensional non-semi-simple
group. We obtain conformal \s-models in spacetime dimensions (with
exact central charge ) by axially and vectorially gauging a
one-dimensional subgroup. The model obtained in the axial gauging is related to
the black string after a correlated limit is taken in the latter model. By
identifying the CFT corresponding to these \s-models we compute the exact
expressions for the metric and dilaton fields. All of our models can be mapped
to flat spacetimes with zero antisymmetric tensor and dilaton fields via
duality transformations.Comment: 17 pages, harvmac, THU-93/30 (The discussion and reference sections
are expanded
Conformal sigma models corresponding to gauged Wess-Zumino-Witten theories
We develop a field-theoretical approach to determination of the background
target space fields corresponding to general coset conformal theories
described by gauged WZW models. The basic idea is to identify the effective
action of a gauged WZW theory with the effective action of a sigma model. The
derivation of the quantum effective action in the gauged WZW theory is
presented in detail, both in the bosonic and in the supersymmetric cases. We
explain why and how one can truncate the effective action by omitting most of
the non-local terms (thus providing a justification for some previous
suggestions). The resulting metric, dilaton and the antisymmetric tensor are
non-trivial functions of (or ) and represent a large class of
conformal sigma models. The exact expressions for the fields in the
sypersymmetric case are equal to the leading order (`semiclassical') bosonic
expressions (with no shift of ). An explicit form in which we find the sigma
model couplings makes it possible to prove that the metric and the dilaton are
equivalent to the fields which are obtained in the operator approach, i.e. by
identifying the -operator of the conformal theory with a Klein-Gordon
operator in a background. The metric can be considered as a `deformation' of an
invariant metric on the coset space and the dilaton can be in general
represented in terms of the logarithm of the ratio of the determinants of the
`deformed' and `round' metrics.Comment: 56 pages, harvmac (b), CERN-TH.6804/93 (minor changes in sects.
2,4,6
Reproduction triggers adaptive increases in body size in female mole-rats
In social mole-rats, breeding females are larger and more elongated than non-breeding female helpers. This status-related morphological divergence is thought to arise from modifications of skeletal growth following the death or removal of the previous breeder and the transition of their successors from a non-breeding to a breeding role. However, it is not clear what changes in growth are involved, whether they are stimulated by the relaxation of reproductive suppression or by changes in breeding status, or whether they are associated with fecundity increases. Here, we show that, in captive Damaraland mole-rats (Fukomys damarensis), where breeding was experimentally controlled in age-matched siblings, individuals changed in size and shape through a lengthening of the lumbar vertebrae when they began breeding. This skeletal remodelling results from changes in breeding status because (i) females removed from a group setting and placed solitarily showed no increases in growth and (ii) females dispersing from natural groups that have not yet bred do not differ in size and shape from helpers in established groups. Growth patterns consequently resemble other social vertebrates where contrasts in size and shape follow the acquisition of the breeding role. Our results also suggest that the increases in female body size provide fecundity benefits. Similar forms of socially responsive growth might be more prevalent in vertebrates than is currently recognized, but the extent to which this is the case, and the implications for the structuring of mammalian dominance hierarchies, are as yet poorly understood.The Kalahari Mole-rat Project is supported by a European Research Council Grant awarded to T.C.-B. (no. 294494); J.T. was funded by a Natural Environment Research Council Doctoral Training Program; parts of the fieldwork were funded by a British Ecological Society Grant awarded to Markus Zöttl (no. 5301/6343).http://rspb.royalsocietypublishing.org2019-06-13hj2018Mammal Research InstituteZoology and Entomolog
On Non-Abelian Duality
A general study of non-abelian duality is presented. We first identify a
possible obstruction to the conformal invariance of the dual theory for
non-semisimple groups. We construct the exact non-abelian dual for any
Wess-Zumino-Witten (WZW) model for any anomaly free subgroup, and the
corresponding extension for coset conformal field theories. We characterize the
exact non-abelian dual for -models with chiral isometries and extend
the standard notion of duality to anomalous subgroups of
WZW models, thus giving a way of constructing dual transformations for
different groups on the left and on the right. We also present some new
examples of non-abelian duality for four-dimensional gravitational instantons.Comment: 34 p, LaTex, preprint CERN-TH-7204/94, problems with the generation
of ps and pdf solve
Semiclassical vs. Exact Solutions of Charged Black Hole in Four Dimensions and Exact O(d,d) Duality
We derive a charged black hole solution in four dimensions described by
WZW coset model. Using the algebraic
Hamiltonian method we calculate the corresponding solution that is exact to all
orders in . It is shown that unlike the 2D black hole, the
singularity remains also in the exact solution, and moreover, in some range of
the gauge parameter the space-time does not fulfil the cosmic censor
conjecture, we find a naked singularity outside the black hole. Exact
dual models are derived as well, one of them describes a 4D space-time with a
naked singularity. Using the algebraic Hamiltonian approach we also find the
exact to all orders transformation of the metric and the dilaton field
for general WZW coset models and show the correction with respect to the
transformations in one loop order.Comment: 42 pages, (typographical errors in pages 33 and 35
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