86 research outputs found
Renormalization Group Analysis of \rho-Meson Properties at Finite Density
We calculate the density dependence of the -meson mass and coupling
constant() for -nucleon-nucleon vertex at one loop using the
lagrangian where the -meson is included as a dynamical gauge boson of a
hidden local symmetry. From the condition that thermodynamic potential should
not depend on the arbitrary energy scale, renormalization scale, one can
construct a renormalization group equation for the thermodynamic potential and
argue that the various renormalization group coefficients are functions of the
density or temperature. We calculate the -function for
-nucleon-nucleon coupling constant () and -function
for -meson mass (). We found that the -meson mass
and the coupling constant for drop as density increases in the
low energy limit.Comment: 24 pages, 10 figures, revised versio
Propagators for p-forms in AdS_{2p+1} and correlation functions in the AdS_7/(2,0) CFT correspondence
In AdS_{2p+1} we construct propagators for p-forms whose lagrangians contain
terms of the form A / d A. In particular we explore the case of forms
satisfying ``self duality in odd dimensions'', and the case of forms with a
topological mass term. We point out that the ``complete'' set of maximally
symmetric bitensors previously used in all the other propagator papers is
incomplete - there exists another bitensor which can and does appear in the
formulas for the propagators in this particular case. Nevertheless, its
presence does not affect the other propagators computed so far.
On the AdS side of the correspondence we compute the 2 and 3 point functions
involving the self-dual tensor of the maximal 7d gauged supergravity (sugra),
S_{\mu\nu\rho}. Since the 7 dimensional antisymmetric self-dual tensor obeys
first order field equations (S + * d S=0), to get a nonvanishing 2 point
function we add a certain boundary term (to satisfy the variational principle
on a manifold with boundary) to the 7d action. The 3 point functions we compute
are of the type SSB and SBB, describing vertex interactions with the gauge
fields B_{\mu}.Comment: 21 pages, Latex file, one reference adde
Bound States in the AdS/CFT Correspondence
We consider a massive scalar field theory in anti-de Sitter space, in both
minimally and non-minimally coupled cases. We introduce a relevant double-trace
perturbation at the boundary, by carefully identifying the correct source and
generating functional for the corresponding conformal operator. We show that
such relevant double-trace perturbation introduces changes in the coefficients
in the boundary terms of the action, which in turn govern the existence of a
bound state in the bulk. For instance, we show that the usual action,
containing no additional boundary terms, gives rise to a bound state, which can
be avoided only through the addition of a proper boundary term. Another
notorious example is that of a conformally coupled scalar field, supplemented
by a Gibbons-Hawking term, for which there is no associated bound state. In
general, in both minimally and non-minimally coupled cases, we explicitly
compute the boundary terms which give rise to a bound state, and which ones do
not. In the non-minimally coupled case, and when the action is supplemented by
a Gibbons-Hawking term, this also fixes allowed values of the coupling
coefficient to the metric. We interpret our results as the fact that the
requirement to satisfy the Breitenlohner-Freedman bound does not suffice to
prevent tachyonic behavior from existing in the bulk, as it must be
supplemented by additional conditions on the coefficients in the boundary terms
of the action.Comment: 32 pages, Latex. v2: added comments and clarifications, minor
changes. v3: corrected wrong result in the non-minimally coupled case, added
reference, minor changes. v4: Added new results and discussions, parts of the
paper are rewritten. Final version to be published in Phys.Rev.
Jack superpolynomials with negative fractional parameter: clustering properties and super-Virasoro ideals
The Jack polynomials P_\lambda^{(\alpha)} at \alpha=-(k+1)/(r-1) indexed by
certain (k,r,N)-admissible partitions are known to span an ideal I^{(k,r)}_N of
the space of symmetric functions in N variables. The ideal I^{(k,r)}_N is
invariant under the action of certain differential operators which include half
the Virasoro algebra. Moreover, the Jack polynomials in I^{(k,r)}_N admit
clusters of size at most k: they vanish when k+1 of their variables are
identified, and they do not vanish when only k of them are identified. We
generalize most of these properties to superspace using orthogonal
eigenfunctions of the supersymmetric extension of the trigonometric
Calogero-Moser-Sutherland model known as Jack superpolynomials. In particular,
we show that the Jack superpolynomials P_{\Lambda}^{(\alpha)} at
\alpha=-(k+1)/(r-1) indexed by certain (k,r,N)-admissible superpartitions span
an ideal {\mathcal I}^{(k,r)}_N of the space of symmetric polynomials in N
commuting variables and N anticommuting variables. We prove that the ideal
{\mathcal I}^{(k,r)}_N is stable with respect to the action of the
negative-half of the super-Virasoro algebra. In addition, we show that the Jack
superpolynomials in {\mathcal I}^{(k,r)}_N vanish when k+1 of their commuting
variables are equal, and conjecture that they do not vanish when only k of them
are identified. This allows us to conclude that the standard Jack polynomials
with prescribed symmetry should satisfy similar clustering properties. Finally,
we conjecture that the elements of {\mathcal I}^{(k,2)}_N provide a basis for
the subspace of symmetric superpolynomials in N variables that vanish when k+1
commuting variables are set equal to each other.Comment: 36 pages; the main changes in v2 are : 1) in the introduction, we
present exceptions to an often made statement concerning the clustering
property of the ordinary Jack polynomials for (k,r,N)-admissible partitions
(see Footnote 2); 2) Conjecture 14 is substantiated with the extensive
computational evidence presented in the new appendix C; 3) the various tests
supporting Conjecture 16 are reporte
Kaluza-Klein Holography
We construct a holographic map between asymptotically AdS_5 x S^5 solutions
of 10d supergravity and vacuum expectation values of gauge invariant operators
of the dual QFT. The ingredients that enter in the construction are (i) gauge
invariant variables so that the KK reduction is independent of any choice of
gauge fixing; (ii) the non-linear KK reduction map from 10 to 5 dimensions
(constructed perturbatively in the number of fields); (iii) application of
holographic renormalization. A non-trivial role in the last step is played by
extremal couplings. This map allows one to reliably compute vevs of operators
dual to any KK fields. As an application we consider a Coulomb branch solution
and compute the first two non-trivial vevs, involving operators of dimension 2
and 4, and reproduce the field theory result, in agreement with
non-renormalization theorems. This constitutes the first quantitative test of
the gravity/gauge theory duality away from the conformal point involving a vev
of an operator dual to a KK field (which is not one of the gauged supergravity
fields).Comment: 47 pages, v2: minor improvements, version to appear in JHE
On the Exact Evaluation of Certain Instances of the Potts Partition Function by Quantum Computers
We present an efficient quantum algorithm for the exact evaluation of either
the fully ferromagnetic or anti-ferromagnetic q-state Potts partition function
Z for a family of graphs related to irreducible cyclic codes. This problem is
related to the evaluation of the Jones and Tutte polynomials. We consider the
connection between the weight enumerator polynomial from coding theory and Z
and exploit the fact that there exists a quantum algorithm for efficiently
estimating Gauss sums in order to obtain the weight enumerator for a certain
class of linear codes. In this way we demonstrate that for a certain class of
sparse graphs, which we call Irreducible Cyclic Cocycle Code (ICCC_\epsilon)
graphs, quantum computers provide a polynomial speed up in the difference
between the number of edges and vertices of the graph, and an exponential speed
up in q, over the best classical algorithms known to date
Categorizing Different Approaches to the Cosmological Constant Problem
We have found that proposals addressing the old cosmological constant problem
come in various categories. The aim of this paper is to identify as many
different, credible mechanisms as possible and to provide them with a code for
future reference. We find that they all can be classified into five different
schemes of which we indicate the advantages and drawbacks.
Besides, we add a new approach based on a symmetry principle mapping real to
imaginary spacetime.Comment: updated version, accepted for publicatio
Professional closure by proxy: the impact of changing educational requirements on class mobility for a cohort of Big 8 partners
Closure events impacting on class mobility may include mechanisms initiated by bodies other than the professional body. The research examines if the introduction of full-time study requirements at universities for aspiring accountants effectively introduced a closure mechanism in the accounting profession. Data was derived from an Oral History study of partners in large firms. The younger partners (born after the Second World War) completed full-time degree study at university, but did not provide evidence of class mobility into the profession. The older cohort, born between 1928 and 1946, completed part-time studies only, few completed a degree, and, in contrast to the younger cohort, shows a perceptible upward movement from lower socio-economic classes into the professional class. This suggests that changing the preferred educational routes for new accountants entering the large chartered accounting (CA) firms compromised the "stepping stone" function of accounting as a portal into the professional class
Dark Energy and Gravity
I review the problem of dark energy focusing on the cosmological constant as
the candidate and discuss its implications for the nature of gravity. Part 1
briefly overviews the currently popular `concordance cosmology' and summarises
the evidence for dark energy. It also provides the observational and
theoretical arguments in favour of the cosmological constant as the candidate
and emphasises why no other approach really solves the conceptual problems
usually attributed to the cosmological constant. Part 2 describes some of the
approaches to understand the nature of the cosmological constant and attempts
to extract the key ingredients which must be present in any viable solution. I
argue that (i)the cosmological constant problem cannot be satisfactorily solved
until gravitational action is made invariant under the shift of the matter
lagrangian by a constant and (ii) this cannot happen if the metric is the
dynamical variable. Hence the cosmological constant problem essentially has to
do with our (mis)understanding of the nature of gravity. Part 3 discusses an
alternative perspective on gravity in which the action is explicitly invariant
under the above transformation. Extremizing this action leads to an equation
determining the background geometry which gives Einstein's theory at the lowest
order with Lanczos-Lovelock type corrections. (Condensed abstract).Comment: Invited Review for a special Gen.Rel.Grav. issue on Dark Energy,
edited by G.F.R.Ellis, R.Maartens and H.Nicolai; revtex; 22 pages; 2 figure
EXTL3 mutations cause skeletal dysplasia, immune deficiency, and developmental delay.
We studied three patients with severe skeletal dysplasia, T cell immunodeficiency, and developmental delay. Whole-exome sequencing revealed homozygous missense mutations affecting exostosin-like 3 (EXTL3), a glycosyltransferase involved in heparan sulfate (HS) biosynthesis. Patient-derived fibroblasts showed abnormal HS composition and altered fibroblast growth factor 2 signaling, which was rescued by overexpression of wild-type EXTL3 cDNA. Interleukin-2-mediated STAT5 phosphorylation in patients' lymphocytes was markedly reduced. Interbreeding of the extl3-mutant zebrafish (box) with Tg(rag2:green fluorescent protein) transgenic zebrafish revealed defective thymopoiesis, which was rescued by injection of wild-type human EXTL3 RNA. Targeted differentiation of patient-derived induced pluripotent stem cells showed a reduced expansion of lymphohematopoietic progenitor cells and defects of thymic epithelial progenitor cell differentiation. These data identify EXTL3 mutations as a novel cause of severe immune deficiency with skeletal dysplasia and developmental delay and underline a crucial role of HS in thymopoiesis and skeletal and brain development
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