1,734,916 research outputs found
Malagasy Time Conceptions
In this paper I discuss Øyvind Dahl’s argument (1995,1999) for the conclusion that Malagasy people conceive of the future as coming from behind them and not as being before them as most worldviews do. I argue that we have good reason not to attribute this view to Malagasy people. First, it would mark an inefficient and anomalous way of keeping track of the past and future. Second, the linguistic and testimonial evidence presented by Dahl doesn’t support the conclusion. Even though this specific argument fails, Dahl has many enlightening things to say about Malagasy time conceptions, such as the various time-conceptions that figure more predominantly in their worldview as opposed to the general modern Western worldview. Dahl is right that successful communication for Westerners in Madagascar requires understanding that the Malagasy worldview is structured more by an event-related conception of time than the general modern Western worldview. I also show in this paper that the three time conceptions Dahl outlines are relevant to living a good life
Chaotic Compilation for Encrypted Computing: Obfuscation but Not in Name
An `obfuscation' for encrypted computing is quantified exactly here, leading
to an argument that security against polynomial-time attacks has been achieved
for user data via the deliberately `chaotic' compilation required for security
properties in that environment. Encrypted computing is the emerging science and
technology of processors that take encrypted inputs to encrypted outputs via
encrypted intermediate values (at nearly conventional speeds). The aim is to
make user data in general-purpose computing secure against the operator and
operating system as potential adversaries. A stumbling block has always been
that memory addresses are data and good encryption means the encrypted value
varies randomly, and that makes hitting any target in memory problematic
without address decryption, yet decryption anywhere on the memory path would
open up many easily exploitable vulnerabilities. This paper `solves (chaotic)
compilation' for processors without address decryption, covering all of ANSI C
while satisfying the required security properties and opening up the field for
the standard software tool-chain and infrastructure. That produces the argument
referred to above, which may also hold without encryption.Comment: 31 pages. Version update adds "Chaotic" in title and throughout
paper, and recasts abstract and Intro and other sections of the text for
better access by cryptologists. To the same end it introduces the polynomial
time defense argument explicitly in the final section, having now set that
denouement out in the abstract and intr
Disentanglement by Dissipative Open System Dynamics
This paper investigates disentanglement as a result of evolution according to
a class of master equations which include dissipation and interparticle
interactions. Generalizing an earlier result of Di\'{o}si, the time taken for
complete disentanglement is calculated (i.e. for disentanglement from any other
system). The dynamics of two harmonically coupled oscillators is solved in
order to study the competing effects of environmental noise and interparticle
coupling on disentanglement. An argument based on separability conditions for
gaussian states is used to arrive at a set of conditions on the couplings
sufficient for all initial states to disentangle for good after a finite time.Comment: Paper in conjunction with and following on from P.J. Dodd and J.J.
Halliwell: quant-ph/031206
Halo bias in Lagrangian Space: Estimators and theoretical predictions
We present several methods to accurately estimate Lagrangian bias parameters
and substantiate them using simulations. In particular, we focus on the
quadratic terms, both the local and the non local ones, and show the first
clear evidence for the latter in the simulations. Using Fourier space
correlations, we also show for the first time, the scale dependence of the
quadratic and non-local bias coefficients. For the linear bias, we fit for the
scale dependence and demonstrate the validity of a consistency relation between
linear bias parameters. Furthermore we employ real space estimators, using both
cross-correlations and the Peak-Background Split argument. This is the first
time the latter is used to measure anisotropic bias coefficients. We find good
agreement for all the parameters among these different methods, and also good
agreement for local bias with ESP theory predictions. We also try to
exploit possible relations among the different bias parameters. Finally, we
show how including higher order bias reduces the magnitude and scale dependence
of stochasticity of the halo field.Comment: 13 pages, 12 figure
Wave turbulence and Bose-Einstein condensates
Asymptotic behavior of a class of nonlinear Schr\"odinger equations are
studied. Particular cases of 1D weakly focusing and Bose-Einstein condensates
are considered. A statistical approach is presented to describe the stationary
probability density of a discretized finite system. Using a maximum entropy
argument, the theory predicts that the statistical equilibrium is described by
energy equivalued fluctuation modes around the coherent structure minimizing
the Hamiltonian of the system. Good quantitative agreement is found with
numerical simulations. In particular, the particle number spectral density
follows an effective law for the asymptotic large time averaged
solutions. Transient dynamics from a given initial condition to the
statistically steady regime shows rapid oscillation of the condensate
The gravitino abundance in supersymmetric `new' inflation models
We consider the abundance of gravitinos created from the vacuum fluctuation,
in a class of `new' inflation models for which global supersymmetry is a good
approximation. Immediately after inflation, gravitinos are produced, with
number density determined by equations recently presented by Kallosh et. al.
(hep-th/9907124) and Giudice et. al. (hep-ph/9907510). Unless reheating
intervenes, creation may continue, maintaining about the same number density,
until the Hubble parameter falls below the gravitino mass. In any case, the
abundance of gravitinos created from the vacuum fluctuation exceeds the
abundance from thermal collisions in a significant regime of parameter space,
leading to tighter cosmological constraints.Comment: 9 pages latex. Same results but argument for late-time creation now
appears in hep-ph/991231
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