1,852,921 research outputs found
Nonparametric bootstrapping of the reliability function for multiple copies of a repairable item modeled by a birth process
Nonparametric bootstrap inference is developed for the reliability function estimated from censored, nonstationary failure time data for multiple copies of repairable items. We assume that each copy has a known, but not necessarily the same, observation period; and upon failure of one copy, design modifications are implemented for all copies operating at that time to prevent further failures arising from the same fault. This implies that, at any point in time, all operating copies will contain the same set of faults. Failures are modeled as a birth process because there is a reduction in the rate of occurrence at each failure. The data structure comprises a mix of deterministic and random censoring mechanisms corresponding to the known observation period of the copy, and the random censoring time of each fault. Hence, bootstrap confidence intervals and regions for the reliability function measure the length of time a fault can remain within the item until realization as failure in one of the copies. Explicit formulae derived for the re-sampling probabilities greatly reduce dependency on Monte-Carlo simulation. Investigations show a small bias arising in re-sampling that can be quantified and corrected. The variability generated by the re-sampling approach approximates the variability in the underlying birth process, and so supports appropriate inference. An illustrative example describes application to a problem, and discusses the validity of modeling assumptions within industrial practice
Bound states and the classical double copy
We extend the perturbative classical double copy to the analysis of bound
systems. We first obtain the leading order perturbative gluon radiation field
sourced by a system of interacting color charges in arbitrary time dependent
orbits, and test its validity by taking relativistic bremsstrahlung and
non-relativistic bound state limits. By generalizing the color to kinematic
replacement rules recently used in the context of classical bremsstrahlung, we
map the gluon emission amplitude to the radiation fields of dilaton gravity
sourced by interacting particles in generic (self-consistent) orbits. As an
application, we reproduce the leading post-Newtonian radiation fields and
energy flux for point masses in non-relativistic orbits from the double copy of
gauge theory.Comment: 9 pages, 1 figure, minor revisions to section II
Asymptotic Flatness, Little String Theory, and Holography
We argue that any non-gravitational holographic dual to asymptotically flat
string theory in -dimensions naturally resides at spacelike infinity. Since
spacelike infinity can be resovled as a -dimensional timelike
hyperboloid (i.e., as a copy of de Sitter space in dimensions), the
dual theory is defined on a Lorentz signature spacetime. Conceptual issues
regarding such a duality are clarified by comparison with linear dilaton
boundary conditions, such as those dual to little string theory. We compute
both time-ordered and Wightman boundary 2-point functions of operators dual to
massive scalar fields in the asymptotically flat bulk.Comment: 27 pages, 2 figures. Explicit discussion added of using the Wightman
function method to calculate time-ordered boundary 2-point functions. The
resulting branch cuts are linked to the bulk spectrum of state
Gauge theory of things alive and universal dynamics
Positing complex adaptive systems made of agents with relations between them
that can be composed, it follows that they can be described by gauge theories
similar to elementary particle theory and general relativity. By definition, a
universal dynamics is able to determine the time development of any such system
without need for further specification. The possibilities are limited, but one
of them - reproduction fork dynamics - describes DNA replication and is the
basis of biological life on earth. It is a universal copy machine and a
renormalization group fixed point. A universal equation of motion in continuous
time is also presented.Comment: 13 pages, latex, uses fleqn.sty (can be removed without harm
Performance of FORTRAN floating-point operations on the Flex/32 multicomputer
A series of experiments has been run to examine the floating-point performance of FORTRAN programs on the Flex/32 (Trademark) computer. The experiments are described, and the timing results are presented. The time required to execute a floating-point operation is found to vary considerbaly depending on a number of factors. One factor of particular interest from an algorithm design standpoint is the difference in speed between common memory accesses and local memory accesses. Common memory accesses were found to be slower, and guidelines are given for determinig when it may be cost effective to copy data from common to local memory
External Inversion, Internal Inversion, and Reflection Invariance
Having in mind that physical systems have different levels of structure we
develop the concept of external, internal and total improper Lorentz
transformation (space inversion and time reversal). A particle obtained from
the ordinary one by the application of internal space inversion or time
reversal is generally a different particle. From this point of view the
intrinsic parity of a nuclear particle (`elementary particle') is in fact the
external intrinsic parity, if we take into account the internal structure of a
particle. We show that non-conservation of the external parity does not
necessarily imply non-invariance of nature under space inversion. The
conventional theory of beta-decay can be corrected by including the internal
degrees of freedom to become invariant under total space inversion, though not
under the external one.Comment: 15 pages. An early proposal of "mirror matter", published in 1974.
This is an exact copy of the published paper. I am posting it here because of
the increasing interest in the "exact parity models" and its experimental
consequence
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