19,322 research outputs found
A Matrix Model for Type 0 Strings
A matrix model for type 0 strings is proposed. It consists in making a
non-supersymmetric orbifold projection in the Yang-Mills theory and identifying
the infrared configurations of the system at infinite coupling with strings.
The correct partition function is calculated. Also, the usual spectrum of
branes is found. Both type A and B models are constructed. The model in a torus
contains all the degrees of freedom and interpolates between the four string
theories (IIA, IIB, 0A, 0B) and the M theory as different limits are taken.Comment: 13 pages, one figure. Also available at
http://condmat1.ciencias.uniovi.es
Magnetic Thomas-Fermi-Weizs\"acker model for quantum dots: a comparison with Kohn-Sham ground states
The magnetic extension of the Thomas-Fermi-Weizs\"acker kinetic energy is
used within density-functional-theory to numerically obtain the ground state
densities and energies of two-dimensional quantum dots. The results are
thoroughly compared with the microscopic Kohn-Sham ones in order to assess the
validity of the semiclassical method. Circular as well as deformed systems are
considered.Comment: EPJ LateX, revised EPJ-
Distances on the tropical line determined by two points
Let . Write if is a multiple of
. Two different points and in uniquely
determine a tropical line , passing through them, and stable under
small perturbations. This line is a balanced unrooted semi--labeled tree on
leaves. It is also a metric graph.
If some representatives and of and are the first and second
columns of some real normal idempotent order matrix , we prove that the
tree is described by a matrix , easily obtained from . We also
prove that is caterpillar. We prove that every vertex in
belongs to the tropical linear segment joining and . A vertex, denoted
, closest (w.r.t tropical distance) to exists in . Same for
. The distances between pairs of adjacent vertices in and the
distances \dd(p,pq), \dd(qp,q) and \dd(p,q) are certain entries of the
matrix . In addition, if and are generic, then the tree
is trivalent. The entries of are differences (i.e., sum of principal
diagonal minus sum of secondary diagonal) of order 2 minors of the first two
columns of .Comment: New corrected version. 31 pages and 9 figures. The main result is
theorem 13. This is a generalization of theorem 7 to arbitrary n. Theorem 7
was obtained with A. Jim\'enez; see Arxiv 1205.416
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