15,305 research outputs found
Cones, Tri-Sasakian Structures and Superconformal Invariance
In this note we show that rigid N=2 superconformal hypermultiplets must have
target manifolds which are cones over tri-Sasakian metrics. We comment on the
relation of this work to cone-branes and the AdS/CFT correspondence.Comment: 10 pages, Latex2
Isometric Embedding of BPS Branes in Flat Spaces with Two Times
We show how non-near horizon p-brane theories can be obtained from two
embedding constraints in a flat higher dimensional space with 2 time
directions. In particular this includes the construction of D3 branes from a
flat 12-dimensional action, and M2 and M5 branes from 13 dimensions. The
worldvolume actions are determined by constant forms in the higher dimension,
reduced to the usual expressions by Lagrange multipliers. The formulation
affords insight in the global aspects of the spacetime geometries and makes
contact with recent work on two-time physics.Comment: 29 pages, 10 figures, Latex using epsf.sty and here.sty; v2:
reference added and some small correction
Conformal Carroll groups
Conformal extensions of Levy-Leblond's Carroll group, based on geometric
properties analogous to those of Newton-Cartan space-time are proposed. The
extensions are labelled by an integer . This framework includes and extends
our recent study of the Bondi-Metzner-Sachs (BMS) and Newman-Unti (NU) groups.
The relation to Conformal Galilei groups is clarified. Conformal Carroll
symmetry is illustrated by "Carrollian photons". Motion both in the
Newton-Cartan and Carroll spaces may be related to that of strings in the
Bargmann space.Comment: 31 pages, no figures. Minor misprints corrected and clarifications
added. To be published in J. Phys.
Conformal Carroll groups and BMS symmetry
The Bondi-Metzner-Sachs (BMS) group is shown to be the conformal extension of
Levy-Leblond's "Carroll" group. Further extension to the Newman-Unti (NU) group
is also discussed in the Carroll framework.Comment: 10 pages, no figure. Fast Track COmmunication, to appear in Class.
Quant. Gra
Inflation from String/M-Theory Compactification?
We present some exact scalar potentials for the dimensionally reduced theory
and examine the possibility of obtaining accelerating 4d cosmology from
String/M-theory, more generally, hyperbolic and flux compactification. In the
hyperbolic case, even in the zero-flux limit, the scalar potential is positive
for the 4d effective theory as required to get an accelerating universe, and
thereby evading the ``no-go theorem'' given for static internal space. When we
turn on the gauge fields as source terms at the cosmological background with
potential V\propto exp(-2c\phi), we find eternally accelerating cosmologies
when the 4d space-time is flat and c\geq 1, or hyperbolic and 1<c<\sqrt{2}.Comment: 3 pp. espcrc2.sty. Minor typos corrected and Ref. added. To appear in
proceedings of Lattice 2003 (Gravity), Tsukuba, Japan, July 200
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