1,543 research outputs found
Effects of scale in predicting global structural response
Analytical techniques for scale-up effects were reviewed. The advantages and limitations of applying the principles of similitude to composite structures is summarized and illustrated by simple examples. An analytical procedure was formulated to design scale models of an axially compressed composite cylinder. A building-block approach was outlined where each structural detail is analyzed independently and the probable failure sequence of a selected component is predicted, taking into account load redistribution subsequent to first element failure. Details of this building-block approach are under development
Four Dimensional Supergravity from String Theory
A derivation of N=1 supergravity action from string theory is presented.
Starting from a Nambu-Goto bosonic string, matter field is introduced to obtain
a superstring in four dimension. The excitation quanta of this string contain
graviton and the gravitino. Using the principle of equivalence, the action in
curved space time are found and the sum of them is the Deser-Zumino N=1
supergravity action. The energy tensor is Lorentz invariant due to
supersymmetry.Comment: 9 page
Stabilizing Hadron Resonance Gas Models against Future Discoveries
We examine the stability of hadron resonance gas models by extending them to
take care of undiscovered resonances through the Hagedorn formula. We find that
the influence of unknown resonances on thermodynamics is large but bounded.
Hadron resonance gases are internally consistent up to a temperature higher
than the cross over temperature in QCD; but by examining quark number
susceptibilities we find that their region of applicability seems to end even
below the QCD cross over. We model the decays of resonances and investigate the
ratios of particle yields in heavy-ion collisions. We find that observables
such as hydrodynamics and hadron yield ratios change little upon extending the
model. As a result, heavy-ion collisions at RHIC and LHC are insensitive to a
possible exponential rise in the hadronic density of states, thus increasing
the stability of the predictions of hadron resonance gas models
Temperature enhanced persistent currents and " periodicity"
We predict a non-monotonous temperature dependence of the persistent currents
in a ballistic ring coupled strongly to a stub in the grand canonical as well
as in the canonical case. We also show that such a non-monotonous temperature
dependence can naturally lead to a periodicity of the persistent
currents, where =h/e. There is a crossover temperature , below
which persistent currents increase in amplitude with temperature while they
decrease above this temperature. This is in contrast to persistent currents in
rings being monotonously affected by temperature. is parameter-dependent
but of the order of , where is the level spacing
of the isolated ring. For the grand-canonical case is half of that for
the canonical case.Comment: some typos correcte
Three Generations of SUSY Standard Model of Nambu-Goto String
A four dimensional Superstring is constructed starting from a twenty six
dimensional bosonic string. Fermions are introduced by noting the Manselstam's
proof of equivalence of two fermions to one boson in 1+1 dimensions. The action
of the superstring is invariant under SO(6) SO(5). It has four bosonic
coordinates and twenty four Majorana fermions of SO(3,1) representing two
transverse modes of super fermions and conformal ghosts (b,c). The super
conformal ghosts () are the quanta of an extended Hilbert space
of the remaining longitudinal modes of two superfermions. The massless spectrum
obtained by quantising the action, contain vector mesons which are generators
of the SO(6)SO(5). Using Wilson loops, this product group is proven to
descend to without breaking
supersymmetry.Thus there are just three generations of quarks and leptons.Comment: 11 page
Hot String Soup
Above the Hagedorn energy density closed fundamental strings form a long
string phase. The dynamics of weakly interacting long strings is described by a
simple Boltzmann equation which can be solved explicitly for equilibrium
distributions. The average total number of long strings grows logarithmically
with total energy in the microcanonical ensemble. This is consistent with
calculations of the free single string density of states provided the
thermodynamic limit is carefully defined. If the theory contains open strings
the long string phase is suppressed.Comment: 13 pages, no figures, uses LaTex, some errors in equations have been
corrected, NSF-ITP-94-83, UCSBTH-94-3
A Bulk-Parallel Priority Queue in External Memory with STXXL
We propose the design and an implementation of a bulk-parallel external
memory priority queue to take advantage of both shared-memory parallelism and
high external memory transfer speeds to parallel disks. To achieve higher
performance by decoupling item insertions and extractions, we offer two
parallelization interfaces: one using "bulk" sequences, the other by defining
"limit" items. In the design, we discuss how to parallelize insertions using
multiple heaps, and how to calculate a dynamic prediction sequence to prefetch
blocks and apply parallel multiway merge for extraction. Our experimental
results show that in the selected benchmarks the priority queue reaches 75% of
the full parallel I/O bandwidth of rotational disks and and 65% of SSDs, or the
speed of sorting in external memory when bounded by computation.Comment: extended version of SEA'15 conference pape
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