12,774 research outputs found
Cosmological space-times with resolved Big Bang in Yang-Mills matrix models
We present simple solutions of IKKT-type matrix models that can be viewed as
quantized homogeneous and isotropic cosmological space-times, with finite
density of microstates and a regular Big Bang (BB). The BB arises from a
signature change of the effective metric on a fuzzy brane embedded in
Lorentzian target space, in the presence of a quantized 4-volume form. The
Hubble parameter is singular at the BB, and becomes small at late times. There
is no singularity from the target space point of view, and the brane is
Euclidean "before" the BB. Both recollapsing and expanding universe solutions
are obtained, depending on the mass parameters.Comment: 22 pages, 4 figures. V2,V3: improved discussion, typos fixed. V3:
published versio
Quantized open FRW cosmology from Yang-Mills matrix models
We present simple solutions of IKKT-type matrix models describing a quantized
homogeneous and isotropic cosmology with , finite density of microstates
and a resolved Big Bang. At late times, a linear coasting cosmology is obtained, which is remarkably close to observation. The solution
consists of two sheets with opposite intrinsic chiralities, which are connected
in a Euclidean pre-big bang era.Comment: 5 pages, 1 figure. V2: minor correction
String states, loops and effective actions in noncommutative field theory and matrix models
Refining previous work by Iso, Kawai and Kitazawa, we discuss bi-local string
states as a tool for loop computations in noncommutative field theory and
matrix models. Defined in terms of coherent states, they exhibit the stringy
features of noncommutative field theory. This leads to a closed form for the
1-loop effective action in position space, capturing the long-range non-local
UV/IR mixing for scalar fields. The formalism applies to generic fuzzy spaces.
The non-locality is tamed in the maximally supersymmetric IKKT or IIB model,
where it gives rise to supergravity. The linearized supergravity interactions
are obtained directly in position space at one loop using string states on
generic noncommutative branes.Comment: 31 pages, 2 figure
One-loop stabilization of the fuzzy four-sphere via softly broken SUSY
We describe a stabilization mechanism for fuzzy in the Euclidean IIB
matrix model due to vacuum energy in the presence of a positive mass term. The
one-loop effective potential for the radius contains an attractive contribution
attributed to supergravity, while the mass term induces a repulsive
contribution for small radius due to SUSY breaking. This leads to a
stabilization of the radius. The mechanism should be pertinent to recent
results on the genesis of 3+1-dimensional space-time in the Minkowskian IIB
model.Comment: 28 pages, 3 figures. V2: typos fixed, improved discussion, published
version. V3,V4: reference adde
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