78 research outputs found
On Modelling Life
We present a theoretical as well as experimental investigation of a
population of self-replicating segments of code subject to random mutation and
survival of the fittest. Under the assumption that such a system constitutes a
minimal system with characteristics of life, we obtain a number of statements
on the evolution of complexity and the trade-off between entropy and
information.Comment: 6 p., postscript with figures (unpack with uufiles), to appear in the
Proc. of ``Artificial Life IV'', MIT Pres
First observations of Polar Mesospheric Echoes at both 31MHz and 53.5MHz over Svalbard (78.2°N 15.1°E)
During summer 2020, observations of the mesosphere using a 53.5 MHz radar on Svalbard, at 78.2°N 15.1°E, revealed the well-known Polar Mesospheric Summer Echoes (PMSE). At the same time, a co-located meteor detection radar, operating at 31 MHz detected corresponding echoes very distinct from those associated with meteor trails. Comparing as many days as possible during 2020, incontestable evidence arose to demonstrate that the meteor detection radar was capable of observing PMSE, although not in the optimised fashion of the 53.5 MHz system. We present examples of results from both systems, supplementing the earlier findings of Swarnalingam et al. (2009), and simultaneously show very first results from this particular geographical location
Response of Planetary Waves and Tides to the 2019 Southern Hemisphere Ssw and q2dw Enhancement in Jan-Feb 2020 Observed by Condor Meteor Radar in Chile and Adelaide Meteor Radar in Australia
A new multi-static meteor radar (CONDOR) has recently been installed in northern Chile. This CONDOR meteor radar (30.3°S, 70.7°W) and the Adelaide meteor radar (35°S, 138°E) have provided longitudinally spaced observations of the mean winds, tides and planetary waves of the PW-tides interaction cases we present here. We have observed a Quasi-6-Day Wave (Q6DW) enhancement in MLT winds at the middle latitudes (30.3°S, 35°S) during the unusual minor South Hemisphere SSW 2019 by the ground-based meteor radars. Tidal analysis also indicates modulation of the Q6DW w/ amplitude ~15 [m/s] and diurnal tides w/ amplitude ~60 [m/s]. Another case we present here is a dominant Quasi-2-Day Wave (Q2DW) with up to 50 [km/s] amplitude occurring in SH summer 2020 and its interaction with the diurnal and semidiurnal tides. The period of this Q2DW activity changes from ~50hr to ~48hr since Jan 19, which suggests the phase locking mechanism [McCormack et al., 2010]. The 24hr-feature and 12hr-feature show off-phase variations during the Q2DW enhancement time with amplitude of ~40 [m/s]
Quantum Information Theory of Entanglement and Measurement
We present a quantum information theory that allows for a consistent
description of entanglement. It parallels classical (Shannon) information
theory but is based entirely on density matrices (rather than probability
distributions) for the description of quantum ensembles. We find that quantum
conditional entropies can be negative for entangled systems, which leads to a
violation of well-known bounds in Shannon information theory. Such a unified
information-theoretic description of classical correlation and quantum
entanglement clarifies the link between them: the latter can be viewed as
``super-correlation'' which can induce classical correlation when considering a
tripartite or larger system. Furthermore, negative entropy and the associated
clarification of entanglement paves the way to a natural information-theoretic
description of the measurement process. This model, while unitary and causal,
implies the well-known probabilistic results of conventional quantum mechanics.
It also results in a simple interpretation of the Kholevo theorem limiting the
accessible information in a quantum measurement.Comment: 26 pages with 6 figures. Expanded version of PhysComp'96 contributio
Complex Langevin Equation and the Many-Fermion Problem
We study the utility of a complex Langevin (CL) equation as an alternative
for the Monte Carlo (MC) procedure in the evaluation of expectation values
occurring in fermionic many-body problems. We find that a CL approach is
natural in cases where non-positive definite probability measures occur, and
remains accurate even when the corresponding MC calculation develops a severe
``sign problem''. While the convergence of CL averages cannot be guaranteed in
principle, we show how convergent results can be obtained in three examples
ranging from simple one-dimensional integrals over quantum mechanical models to
a schematic shell model path integral.Comment: 19 pages, 10 PS figures embedded in tex
- …