11,963 research outputs found
The 1977 Soviet Constitution: A Historical Comparison
Throughout the Soviet Union\u27s history, its four constitutions have been a reflection of the political climate of the particular period. The documents thus viewed provide a historical and political benchmark against which life and thought in the U.S.S.R. may be fairly accurately gauged. When Brezhnev addressed the USSR Supreme Soviet on October 4, 1977, to recommend the inevitable adoption of the 1977 Constitution, he again stressed the historical perspective in which the document must be viewed. He stated: We will adopt the new Constitution on the eve of the 60th anniversary of the Great October Socialist Revolution. This is not merely a coincidence ....The new Constitution, it might be said, is the concentrated result of the entire 60-year development of the Soviet state. It is striking evidence of the fact that the ideas proclaimed by [the] October [Revolution] and Lenin\u27s behests are being successfully implemented.
This article will attempt to analyze the new Basic Law of the U.S.S.R. in light of this historical and political context in which it was obviously intended. The authors, however, will attempt to separate out the legitimate from the rhetorical, and will point out the aspects of the new Constitution which have been included principally for their propaganda value
Reconstruction of universal Drinfeld twists from representations
Universal Drinfeld twists are inner automorphisms which relate the coproduct
of a quantum enveloping algebra to the coproduct of the undeformed enveloping
algebra. Even though they govern the deformation theory of classical symmetries
and have appeared in numerous applications, no twist for a semi-simple quantum
enveloping algebra has ever been computed. It is argued that universal twists
can be reconstructed from their well known representations. A method to
reconstruct an arbitrary element of the enveloping algebra from its irreducible
representations is developed. For the twist this yields an algebra valued
generating function to all orders in the deformation parameter, expressed by a
combination of basic and ordinary hypergeometric functions. An explicit
expression for the universal twist of su(2) is given up to third order.Comment: 24 page
Discovery of a 66 mas Ultracool Binary with Laser Guide Star Adaptive Optics
We present the discovery of 2MASS J21321145+1341584AB as a closely separated
(0.066") very low-mass field dwarf binary resolved in the near-infrared by the
Keck II Telescope using laser guide star adaptive optics. Physical association
is deduced from the angular proximity of the components and constraints on
their common proper motion. We have obtained a near-infrared spectrum of the
binary and find that it is best described by an L5+/-0.5 primary and an
L7.5+/-0.5 secondary. Model-dependent masses predict that the two components
straddle the hydrogen burning limit threshold with the primary likely stellar
and the secondary likely substellar. The properties of this sytem - close
projected separation (1.8+/-0.3 AU) and near unity mass ratio - are consistent
with previous results for very low-mass field binaries. The relatively short
estimated orbital period of this system (~7-12 yr) makes it a good target for
dynamical mass measurements. Interestingly, the system's angular separation is
the tightest yet for any very low-mass binary published from a ground-based
telescope and is the tightest binary discovered with laser guide star adaptive
optics to date.Comment: 10 pages, 3 figures; accepted for publication to A
Schwinger Pair Creation of Particles and Strings
I shortly review the worldline instanton method for calculating Schwinger
pair production rates in (i) one-loop QED (ii) multiloop QED and (iii) one-loop
open string theory.Comment: 8 pages, 3 figures, talk given at XIV Mexican School of Particles and
Fields, November 8 - 12, 2010, Morelia, Mexico, to appear in the conference
proceeding
Momentum dependence in the dynamically assisted Sauter-Schwinger effect
Recently it has been found that the superposition of a strong and slow
electric field with a weaker and faster pulse can significantly enhance the
probability for non-perturbative electron-positron pair creation out of the
vacuum -- the dynamically assisted Sauter-Schwinger effect. Via the WKB method,
we estimate the momentum dependence of the pair creation probability and
compare it to existing numerical results. Besides the theoretical interest, a
better understanding of this pair creation mechanism should be helpful for the
planned experiments aiming at its detection.Comment: 4 pages RevTeX, 1 figur
How Land Surface Characteristics Influence the Development of Flash Drought through the Drivers of Soil Moisture and Vapor Pressure Deficit
As global mean temperature rises, extreme drought events are expected to increasingly affect regions of the United States that are crucial for agriculture, forestry, and natural ecology. A pressing need is to understand and anticipate the conditions under which extreme drought causes catastrophic failure to vegetation in these areas. To better predict drought impacts on ecosystems, we first must understand how specific drivers, namely, atmospheric aridity and soil water stress, affect land surface processes during the evolution of flash drought events. In this study, we evaluated when vapor pressure deficit (VPD) and soil moisture thresholds corresponding to photosynthetic shutdown were crossed during flash drought events across different climate zones and land surface characteristics in the United States. First, the Dynamic Canopy Biophysical Properties (DCBP) model was used to estimate the thresholds that define reduced photosynthesis by assimilating vegetation phenology data from theModerate Resolution Imaging Spectroradiometer (MODIS) to a predictive phenology model. Next, we characterized and quantified flash drought onset, intensity, and duration using the standardized evaporative stress ratio (SESR) and NLDAS-2 reanalysis. Once periods of flash drought were identified, we investigated how VPD and soil moisture coevolved across regions and plant functional types. Results demonstrate that croplands and grasslands tend to be more sensitive to soil water limitations than trees across different regions of the United States. We found that whether VPD or soil moisture was the primary driver of plant water stress during drought was largely region specific. The results of this work will help to inform land managers of early warning signals relevant for specific ecosystems under threat of flash drought events
Using error correction to determine the noise model
Quantum error correcting codes have been shown to have the ability of making
quantum information resilient against noise. Here we show that we can use
quantum error correcting codes as diagnostics to characterise noise. The
experiment is based on a three-bit quantum error correcting code carried out on
a three-qubit nuclear magnetic resonance (NMR) quantum information processor.
Utilizing both engineered and natural noise, the degree of correlations present
in the noise affecting a two-qubit subsystem was determined. We measured a
correlation factor of c=0.5+/-0.2 using the error correction protocol, and
c=0.3+/-0.2 using a standard NMR technique based on coherence pathway
selection. Although the error correction method demands precise control, the
results demonstrate that the required precision is achievable in the
liquid-state NMR setting.Comment: 10 pages, 3 figures. Added discussion section, improved figure
A priori Wannier functions from modified Hartree-Fock and Kohn-Sham equations
The Hartree-Fock equations are modified to directly yield Wannier functions
following a proposal of Shukla et al. [Chem. Phys. Lett. 262, 213-218 (1996)].
This approach circumvents the a posteriori application of the Wannier
transformation to Bloch functions. I give a novel and rigorous derivation of
the relevant equations by introducing an orthogonalizing potential to ensure
the orthogonality among the resulting functions. The properties of these,
so-called a priori Wannier functions, are analyzed and the relation of the
modified Hartree-Fock equations to the conventional, Bloch-function-based
equations is elucidated. It is pointed out that the modified equations offer a
different route to maximally localized Wannier functions. Their computational
solution is found to involve an effort that is comparable to the effort for the
solution of the conventional equations. Above all, I show how a priori Wannier
functions can be obtained by a modification of the Kohn-Sham equations of
density-functional theory.Comment: 7 pages, RevTeX4, revise
- …