200 research outputs found
Artificial intelligence issues related to automated computing operations
Large data processing installations represent target systems for effective applications of artificial intelligence (AI) constructs. The system organization of a large data processing facility at the NASA Marshall Space Flight Center is presented. The methodology and the issues which are related to AI application to automated operations within a large-scale computing facility are described. Problems to be addressed and initial goals are outlined
Optimization of large matrix calculations for execution on the Cray X-MP vector supercomputer
A considerable volume of large computational computer codes were developed for NASA over the past twenty-five years. This code represents algorithms developed for machines of earlier generation. With the emergence of the vector supercomputer as a viable, commercially available machine, an opportunity exists to evaluate optimization strategies to improve the efficiency of existing software. This result is primarily due to architectural differences in the latest generation of large-scale machines and the earlier, mostly uniprocessor, machines. A sofware package being used by NASA to perform computations on large matrices is described, and a strategy for conversion to the Cray X-MP vector supercomputer is also described
W-Algebras of Negative Rank
Recently it has been discovered that the W-algebras (orbifold of) WD_n can be
defined even for negative integers n by an analytic continuation of their
coupling constants. In this letter we shall argue that also the algebras
WA_{-n-1} can be defined and are finitely generated. In addition, we show that
a surprising connection exists between already known W-algebras, for example
between the CP(k)-models and the U(1)-cosets of the generalized
Polyakov-Bershadsky-algebras.Comment: 12 papes, Latex, preprint DFTT-40/9
Space Ultrareliable Modular Computer (SUMC) instruction simulator
Simulator has been constructed as set of quasi-independent modules, regulated by one control module. All machine-dependent functions have been resolved such that simulation package is as machine independent as possible
Classification of Structure Constants for W-algebras from Highest Weights
We show that the structure constants of W-algebras can be grouped according
to the lowest (bosonic) spin(s) of the algebra. The structure constants in each
group are described by a unique formula, depending on a functional parameter
h(c) that is characteristic for each algebra. As examples we give the structure
constants C_{33}^4 and C_{44}^4 for the algebras of type W(2,3,4,...) (that
include the WA_{n-1}-algebras) and the structure constant C_{44}^4 for the
algebras of type W(2,4,...), especially for all the algebras WD_n, WB(0,n),
WB_n and WC_n. It also includes the bosonic projection of the super-Virasoro
algebra and a yet unexplained algebra of type W(2,4,6) found previously.Comment: 18 pages (A4), LaTeX, DFTT-40/9
W-algebras with set of primary fields of dimensions (3, 4, 5) and (3,4,5,6)
We show that that the Jacobi-identities for a W-algebra with primary fields
of dimensions 3, 4 and 5 allow two different solutions. The first solution can
be identified with WA_4. The second is special in the sense that, even though
associative for general value of the central charge, null-fields appear that
violate some of the Jacobi-identities, a fact that is usually linked to
exceptional W-algebras. In contrast we find for the algebra that has an
additional spin 6 field only the solution WA_5.Comment: 17 pages, LaTeX, KCL-TH-92-9, DFFT-70/9
Commuting quantities and exceptional W-algebras
Sets of commuting charges constructed from the current of a U(1) Kac-Moody
algebra are found. There exists a set S_n of such charges for each positive
integer n > 1; the corresponding value of the central charge in the
Feigin-Fuchs realization of the stress tensor is c = 13-6n-6/n. The charges in
each series can be written in terms of the generators of an exceptional
W-algebra.Comment: 27 pages, KCL-TH-92-
Triality in Minimal Model Holography
The non-linear W_{\infty}[\mu] symmetry algebra underlies the duality between
the W_N minimal model CFTs and the hs[\mu] higher spin theory on AdS_3. It is
shown how the structure of this symmetry algebra at the quantum level, i.e. for
finite central charge, can be determined completely. The resulting algebra
exhibits an exact equivalence (a`triality') between three (generically)
distinct values of the parameter \mu. This explains, among other things, the
agreement of symmetries between the W_N minimal models and the bulk higher spin
theory. We also study the consequences of this triality for some of the
simplest W_{\infty}[\mu] representations, thereby clarifying the analytic
continuation between the`light states' of the minimal models and conical defect
solutions in the bulk. These considerations also lead us to propose that one of
the two scalar fields in the bulk actually has a non-perturbative origin.Comment: 29 pages; v2. Typos correcte
Coset Realization of Unifying W-Algebras
We construct several quantum coset W-algebras, e.g. sl(2,R)/U(1) and
sl(2,R)+sl(2,R) / sl(2,R), and argue that they are finitely nonfreely
generated. Furthermore, we discuss in detail their role as unifying W-algebras
of Casimir W-algebras. We show that it is possible to give coset realizations
of various types of unifying W-algebras, e.g. the diagonal cosets based on the
symplectic Lie algebras sp(2n) realize the unifying W-algebras which have
previously been introduced as `WD_{-n}'. In addition, minimal models of WD_{-n}
are studied. The coset realizations provide a generalization of
level-rank-duality of dual coset pairs. As further examples of finitely
nonfreely generated quantum W-algebras we discuss orbifolding of W-algebras
which on the quantum level has different properties than in the classical case.
We demonstrate in some examples that the classical limit according to Bowcock
and Watts of these nonfreely finitely generated quantum W-algebras probably
yields infinitely nonfreely generated classical W-algebras.Comment: 60 pages (plain TeX) (final version to appear in Int. J. Mod. Phys.
A; several minor improvements and corrections - for details see beginning of
file
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