232,742 research outputs found
High-bias stability of monatomic chains
For the metals Au, Pt and Ir it is possible to form freely suspended
monatomic chains between bulk electrodes. The atomic chains sustain very large
current densities, but finally fail at high bias. We investigate the breaking
mechanism, that involves current-induced heating of the atomic wires and
electromigration forces. We find good agreement of the observations for Au
based on models due to Todorov and coworkers. The high-bias breaking of atomic
chains for Pt can also be described by the models, although here the parameters
have not been obtained independently. In the limit of long chains the breaking
voltage decreases inversely proportional to the length.Comment: 7 pages, 5 figure
Strength distribution of repeatedly broken chains
We determine the probability distribution of the breaking strength for chains
of N links, which have been produced by repeatedly breaking a very long chain.Comment: 4 pages, 1 figur
Probing SO(10) symmetry breaking patterns through sfermion mass relations
We consider supersymmetric SO(10) grand unification where the unified gauge
group can break to the Standard Model gauge group through different chains. The
breaking of SO(10) necessarily involves the reduction of the rank, and
consequent generation of non-universal supersymmetry breaking scalar mass
terms. We derive squark and slepton mass relations, taking into account these
non-universal contributions to the sfermion masses, which can help distinguish
between the different chains through which the SO(10) gauge group breaks to the
Standard Model gauge group. We then study some implications of these
non-universal supersymmetry breaking scalar masses for the low energy
phenomenology.Comment: 13 pages, latex using revtex4, contains 2 figures, replaced with
version accepted for publicatio
Hopf algebras and Markov chains: Two examples and a theory
The operation of squaring (coproduct followed by product) in a combinatorial
Hopf algebra is shown to induce a Markov chain in natural bases. Chains
constructed in this way include widely studied methods of card shuffling, a
natural "rock-breaking" process, and Markov chains on simplicial complexes.
Many of these chains can be explictly diagonalized using the primitive elements
of the algebra and the combinatorics of the free Lie algebra. For card
shuffling, this gives an explicit description of the eigenvectors. For
rock-breaking, an explicit description of the quasi-stationary distribution and
sharp rates to absorption follow.Comment: 51 pages, 17 figures. (Typographical errors corrected. Further fixes
will only appear on the version on Amy Pang's website, the arXiv version will
not be updated.
Non-Universal Gaugino Masses in Supersymmetric SO(10)
We consider SUSY SO(10) models in which SUSY breaking occurs via an F-term
which does not transform as an SO(10) singlet. This results in non-universal
GUT-scale gaugino masses leading to a different pattern of sparticle masses
from what is expected in the minimal supergravity model (mSUGRA). We study
three breaking chains of SO(10) down to the standard model through
SU(4)\timesSU(2)\timesSU(2), SU(2)SO(7) and `flipped' SU(5) achieved
by the representations 54 and 210 which appear in the symmetric product of two
SO(10) adjoints. We examine the phenomenological implications of the different
boundary conditions corresponding to the different breaking chains and present
the sparticle spectrum.Comment: 23 pages, 3 figures, 2 tables, corrected typos, discussion and
references added, final version accepted for publication on NP
Ground-State Phase Diagram of Frustrated Anisotropic Quantum Spin Chains
Recent studies on the frustrated quantum spin chains with easy-plane
anisotropy are reviewed. We are particularly interested in novel "chiral"
phases characterized by the spontaneous breaking of the parity symmetry. The
ground-state phase diagrams of the chains are discussed.Comment: 6 pages (ptptex.sty), 3 figures, to appear in Prog. Theor. Phys.
Suppl. (Proc. of the 16th Nishinomiya-Yukawa Symposium and YITP International
Workshop, Nov. 2001
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