164,946 research outputs found
D-instanton induced interactions on a D3-brane
Non-perturbative features of the derivative expansion of the effective action
of a single D3-brane are obtained by considering scattering amplitudes of open
and closed strings. This motivates expressions for the coupling constant
dependence of world-volume interactions of the form (where F
is the Born-Infeld field strength), (where are the
normal coordinates of the D3-brane) and other interactions related by \calN=4
supersymmetry. These include terms that transform with non-trivial modular
weight under Montonen-Olive duality. The leading D-instanton contributions that
enter into these effective interactions are also shown to follow from an
explicit stringy construction of the moduli space action for the
D-instanton/D3-brane system in the presence of D3-brane open-string sources
(but in the absence of a background antisymmetric tensor potential). Extending
this action to include closed-string sources leads to a unified description of
non-perturbative terms in the effective action of the form (embedding
curvature) together with open-string interactions that describe
contributions of the second fundamental form.Comment: 40 pages, harvmac (b), some typos corrected and references adde
What\u27s Going on in Our Prisons?
Additional governmental oversight is urgently needed to truly change the culture of a system that holds 53,000 inmates across 54 prisons in New York State. What goes on inside these prisons is largely hidden from view, and there is little accountability for wrongdoing. The State Legislature should follow the A.B.A.’s guidance and establish a monitoring body with unfettered access to prison facilities, staff, inmates and records in announced or unannounced visits
Source Coding for Quasiarithmetic Penalties
Huffman coding finds a prefix code that minimizes mean codeword length for a
given probability distribution over a finite number of items. Campbell
generalized the Huffman problem to a family of problems in which the goal is to
minimize not mean codeword length but rather a generalized mean known as a
quasiarithmetic or quasilinear mean. Such generalized means have a number of
diverse applications, including applications in queueing. Several
quasiarithmetic-mean problems have novel simple redundancy bounds in terms of a
generalized entropy. A related property involves the existence of optimal
codes: For ``well-behaved'' cost functions, optimal codes always exist for
(possibly infinite-alphabet) sources having finite generalized entropy. Solving
finite instances of such problems is done by generalizing an algorithm for
finding length-limited binary codes to a new algorithm for finding optimal
binary codes for any quasiarithmetic mean with a convex cost function. This
algorithm can be performed using quadratic time and linear space, and can be
extended to other penalty functions, some of which are solvable with similar
space and time complexity, and others of which are solvable with slightly
greater complexity. This reduces the computational complexity of a problem
involving minimum delay in a queue, allows combinations of previously
considered problems to be optimized, and greatly expands the space of problems
solvable in quadratic time and linear space. The algorithm can be extended for
purposes such as breaking ties among possibly different optimal codes, as with
bottom-merge Huffman coding.Comment: 22 pages, 3 figures, submitted to IEEE Trans. Inform. Theory, revised
per suggestions of reader
Quantum features of consciousness, computers and brain
Many people believe that mysterious phenomenon of consciousness may be
connected with quantum features of our world. The present author proposed
so-called Extended Everett's Concept (EEC) that allowed to explain
consciousness and super-consciousness (intuitive knowledge). Brain, according
to EEC, is an interface between consciousness and super-consciousness on the
one part and body on the other part. Relations between all these components of
the human cognitive system are analyzed in the framework of EEC. It is
concluded that technical devices improving usage of super-consciousness
(intuition) may exist.Comment: LATEX, 6 pages; the paper is reported at The 9th WSEAS International
Conference on Applied Computer Science (ACS'09), Genova, Italy, October
17-19, 200
Optimal Prefix Codes for Infinite Alphabets with Nonlinear Costs
Let be a measure of strictly positive probabilities on the set
of nonnegative integers. Although the countable number of inputs prevents usage
of the Huffman algorithm, there are nontrivial for which known methods find
a source code that is optimal in the sense of minimizing expected codeword
length. For some applications, however, a source code should instead minimize
one of a family of nonlinear objective functions, -exponential means,
those of the form , where is the length of
the th codeword and is a positive constant. Applications of such
minimizations include a novel problem of maximizing the chance of message
receipt in single-shot communications () and a previously known problem of
minimizing the chance of buffer overflow in a queueing system (). This
paper introduces methods for finding codes optimal for such exponential means.
One method applies to geometric distributions, while another applies to
distributions with lighter tails. The latter algorithm is applied to Poisson
distributions and both are extended to alphabetic codes, as well as to
minimizing maximum pointwise redundancy. The aforementioned application of
minimizing the chance of buffer overflow is also considered.Comment: 14 pages, 6 figures, accepted to IEEE Trans. Inform. Theor
A GAS OF D-INSTANTONS
A D-instanton is a space-time event associated with world-sheet boundaries
that contributes non-perturbative effects of order to
closed-string amplitudes. Some properties of a gas of D-instantons are
discussed in this paper.Comment: 11 Pages and 3 figures in uuencoded fil
Earned Income Tax Credit: Path Dependence and the Blessing of Undertheorization
Some commentators have lamented that the Earned Income Tax Credit (EITC) is undertheorized—that its purpose is unclear—and that its design is therefore suboptimal. This Note explores the credit’s path-dependent past, which has resulted in a present-day EITC that manifests a diverse, uncoordinated assortment of policy purposes. Although the EITC’s ambiguity of purpose may yield policy inefficiencies, this Note argues that it also produces significant political benefits that would-be reformers who value the EITC’s many societal benefits should take into account before they attempt to enact any major overhaul
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