4,767 research outputs found
The Study of the Pioneer Anomaly: New Data and Objectives for New Investigation
Radiometric tracking data from Pioneer 10 and 11 spacecraft has consistently
indicated the presence of a small, anomalous, Doppler frequency drift,
uniformly changing with a rate of ~6 x 10^{-9} Hz/s; the drift can be
interpreted as a constant sunward acceleration of each particular spacecraft of
a_P = (8.74 \pm 1.33) x 10^{-10} m/s^2. This signal is known as the Pioneer
anomaly; the nature of this anomaly remains unexplained. We discuss the efforts
to retrieve the entire data sets of the Pioneer 10/11 radiometric Doppler data.
We also report on the recently recovered telemetry files that may be used to
reconstruct the engineering history of both spacecraft using original project
documentation and newly developed software tools. We discuss possible ways to
further investigate the discovered effect using these telemetry files in
conjunction with the analysis of the much extended Doppler data. We present the
main objectives of new upcoming study of the Pioneer anomaly, namely i)
analysis of the early data that could yield the direction of the anomaly, ii)
analysis of planetary encounters, that should tell more about the onset of the
anomaly, iii) analysis of the entire dataset, to better determine the anomaly's
temporal behavior, iv) comparative analysis of individual anomalous
accelerations for the two Pioneers, v) the detailed study of on-board
systematics, and vi) development of a thermal-electric-dynamical model using
on-board telemetry. The outlined strategy may allow for a higher accuracy
solution for a_P and, possibly, will lead to an unambiguous determination of
the origin of the Pioneer anomaly.Comment: 43 pages, 40 figures, 3 tables, minor changes before publicatio
Compression and diffusion: a joint approach to detect complexity
The adoption of the Kolmogorov-Sinai (KS) entropy is becoming a popular
research tool among physicists, especially when applied to a dynamical system
fitting the conditions of validity of the Pesin theorem. The study of time
series that are a manifestation of system dynamics whose rules are either
unknown or too complex for a mathematical treatment, is still a challenge since
the KS entropy is not computable, in general, in that case. Here we present a
plan of action based on the joint action of two procedures, both related to the
KS entropy, but compatible with computer implementation through fast and
efficient programs. The former procedure, called Compression Algorithm
Sensitive To Regularity (CASToRe), establishes the amount of order by the
numerical evaluation of algorithmic compressibility. The latter, called Complex
Analysis of Sequences via Scaling AND Randomness Assessment (CASSANDRA),
establishes the complexity degree through the numerical evaluation of the
strength of an anomalous effect. This is the departure, of the diffusion
process generated by the observed fluctuations, from ordinary Brownian motion.
The CASSANDRA algorithm shares with CASToRe a connection with the Kolmogorov
complexity. This makes both algorithms especially suitable to study the
transition from dynamics to thermodynamics, and the case of non-stationary time
series as well. The benefit of the joint action of these two methods is proven
by the analysis of artificial sequences with the same main properties as the
real time series to which the joint use of these two methods will be applied in
future research work.Comment: 27 pages, 9 figure
Lattice Gauge Theories at the Energy Frontier
This White Paper has been prepared as a planning document for the Division of
High Energy Physics of the U. S. Department of Energy. Recent progress in
lattice-based studies of physics beyond the standard model is summarized, and
major current goals of USQCD research in this area are presented. Challenges
and opportunities associated with the recently discovered 126 GeV Higgs-like
particle are highlighted. Computational resources needed for reaching important
goals are described. The document was finalized on February 11, 2013 with
references that are not aimed to be complete, or account for an accurate
historical record of the field.Comment: Submitted for the Snowmass 2013 e-Proceedings with 44 pages, 10
figures, and 3 table
From Knowledge, Knowability and the Search for Objective Randomness to a New Vision of Complexity
Herein we consider various concepts of entropy as measures of the complexity
of phenomena and in so doing encounter a fundamental problem in physics that
affects how we understand the nature of reality. In essence the difficulty has
to do with our understanding of randomness, irreversibility and
unpredictability using physical theory, and these in turn undermine our
certainty regarding what we can and what we cannot know about complex phenomena
in general. The sources of complexity examined herein appear to be channels for
the amplification of naturally occurring randomness in the physical world. Our
analysis suggests that when the conditions for the renormalization group apply,
this spontaneous randomness, which is not a reflection of our limited
knowledge, but a genuine property of nature, does not realize the conventional
thermodynamic state, and a new condition, intermediate between the dynamic and
the thermodynamic state, emerges. We argue that with this vision of complexity,
life, which with ordinary statistical mechanics seems to be foreign to physics,
becomes a natural consequence of dynamical processes.Comment: Phylosophica
Dimension and Dimensional Reduction in Quantum Gravity
A number of very different approaches to quantum gravity contain a common
thread, a hint that spacetime at very short distances becomes effectively two
dimensional. I review this evidence, starting with a discussion of the physical
meaning of "dimension" and concluding with some speculative ideas of what
dimensional reduction might mean for physics.Comment: 33 page draft of solicited review article -- comments and added
references welcome; v2: many added references, minor clean-u
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