474 research outputs found
Lessons from Non-Abelian Plasma Instabilities in Two Spatial Dimensions
Plasma instabilities can play a fundamental role in quark-gluon plasma
equilibration in the high energy (weak coupling) limit. Early simulations of
the evolution of plasma instabilities in non-abelian gauge theory, performed in
one spatial dimension, found behavior qualitatively similar to traditional QED
plasmas. Later simulations of the fully three-dimensional theory found
different behavior, unlike traditional QED plasmas. To shed light on the origin
of this difference, we study the intermediate case of two spatial dimensions.
Depending on how the "two-dimensional'' theory is formulated, we can obtain
either behavior.Comment: 15 pages, 10 figure
The Abelianization of QCD Plasma Instabilities
QCD plasma instabilities appear to play an important role in the
equilibration of quark-gluon plasmas in heavy-ion collisions in the theoretical
limit of weak coupling (i.e. asymptotically high energy). It is important to
understand what non-linear physics eventually stops the exponential growth of
unstable modes. It is already known that the initial growth of plasma
instabilities in QCD closely parallels that in QED. However, once the unstable
modes of the gauge-fields grow large enough for non-Abelian interactions
between them to become important, one might guess that the dynamics of QCD
plasma instabilities and QED plasma instabilities become very different. In
this paper, we give suggestive arguments that non-Abelian self-interactions
between the unstable modes are ineffective at stopping instability growth, and
that the growing non-Abelian gauge fields become approximately Abelian after a
certain stage in their growth. This in turn suggests that understanding the
development of QCD plasma instabilities in the non-linear regime may have close
parallels to similar processes in traditional plasma physics. We conjecture
that the physics of collisionless plasma instabilities in SU(2) and SU(3) gauge
theory becomes equivalent, respectively, to (i) traditional plasma physics,
which is U(1) gauge theory, and (ii) plasma physics of U(1)x U(1) gauge theory.Comment: 36 pages; 15 figures [minor changes made to text, and new figure
added, to reflect published version
The turbulent spectrum created by non-Abelian plasma instabilities
Recent numerical work on the fate of plasma instabilities in weakly-coupled
non-Abelian gauge theory has shown the development of a cascade of energy from
long to short wavelengths. This cascade has a steady-state spectrum, analogous
to the Kolmogorov spectrum for turbulence in hydrodynamics or for energy
cascades in other systems. In this paper, we theoretically analyze processes
responsible for this cascade and find a steady-state spectrum f_k ~ k^-2, where
f_k is the phase-space density of particles with momentum k. The exponent -2 is
consistent with results from numerical simulations. We also discuss
implications of the emerging picture of instability development on the
"bottom-up" thermalization scenario for (extremely high energy) heavy ion
collisions, emphasizing fundamental questions that remain to be answered.Comment: 17 pages, 5 figure
Non-Abelian plasma instabilities: SU(3) vs. SU(2)
We present the first 3+1 dimensional simulations of non-Abelian plasma
instabilities in gauge-covariant Boltzmann-Vlasov equations for the QCD gauge
group SU(3) as well as for SU(4) and SU(5). The real-time evolution of
instabilities for a plasma with stationary momentum-space anisotropy is studied
using a hard-loop effective theory that is discretized in the velocities of
hard particles. We find that the numerically less expensive calculations using
the group SU(2) essentially reproduce the nonperturbative dynamics of
non-Abelian plasma instabilities with higher rank gauge groups provided the
mass parameters of the corresponding hard-loop effective theories are the same.
In particular we find very similar spectra for the turbulent cascade that forms
in the strong-field regime, which is associated with an approximately linear
growth of energy in collective fields. The magnitude of the linear growth
however turns out to increase with the number of colors.Comment: 8 pages, 7 figures; v2: minor changes; accepted for publication in
Phys. Rev.
Fluvial carbon dioxide emission from the Lena River basin during the spring flood
Greenhouse gas (GHG) emission from inland waters of permafrost-affected regions is one of the key factors of circumpolar aquatic ecosystem response to climate warming and permafrost thaw. Riverine systems of central and eastern Siberia contribute a significant part of the water and carbon (C) export to the Arctic Ocean, yet their C exchange with the atmosphere remains poorly known due to lack of in situ GHG concentration and emission estimates. Here we present the results of continuous in situ pCO2 measurements over a 2600 km transect of the Lena River main stem and lower reaches of 20 major tributaries (together representing a watershed area of 1 661 000 km2, 66 % of the Lena's basin), conducted at the peak of the spring flood. The pCO2 in the Lena (range 400-1400 μatm) and tributaries (range 400-1600 μatm) remained generally stable (within ca. 20 %) over the night-day period and across the river channels. The pCO2 in tributaries increased northward with mean annual temperature decrease and permafrost increase; this change was positively correlated with C stock in soil, the proportion of deciduous needleleaf forest, and the riparian vegetation. Based on gas transfer coefficients obtained from rivers of the Siberian permafrost zone (kCombining double low line4.46 md-1), we calculated CO2 emission for the main stem and tributaries. Typical fluxes ranged from 1 to 2 gCm-2d-1 (>99 % CO2, <1 % CH4), which is comparable with CO2 emission measured in the Kolyma, Yukon, and Mackenzie rivers and permafrost-affected rivers in western Siberia. The areal C emissions from lotic waters of the Lena watershed were quantified by taking into account the total area of permanent and seasonal water of the Lena basin (28 000 km2 ). Assuming 6 months of the year to be an open water period with no emission under ice, the annual C emission from the whole Lena basin is estimated as 8.3±2.5 TgCyr-1, which is comparable to the DOC and dissolved inorganic carbon (DIC) lateral export to the Arctic Ocean
Coulomb drag between quantum wires with different electron densities
We study the way back-scattering electron--electron interaction generates
Coulomb drag between quantum wires with different densities. At low temperature
the system can undergo a commensurate-- incommensurate transition as the
potential difference between the two wires passes a critical value
, and this transition is reflected in a marked change in the dependence
of drag resistivity on and . At high temperature a density difference
between the wires suppresses Coulomb drag induced by back scattering, and we
use the Tomonaga--Luttinger model to study this suppression in detail.Comment: 6 pages, 4 figure
Origin of elemental carbon in snow from western Siberia and northwestern European Russia during winter-spring 2014, 2015 and 2016
Short-lived climate forcers have been proven important both for the climate and human health. In particular, black carbon (BC) is an important climate forcer both as an aerosol and when deposited on snow and ice surface because of its strong light absorption. This paper presents measurements of elemental carbon (EC; a measurement-based definition of BC) in snow collected from western Siberia and northwestern European Russia during 2014, 2015 and 2016. The Russian Arctic is of great interest to the scientific community due to the large uncertainty of emission sources there. We have determined the major contributing sources of BC in snow in western Siberia and northwestern European Russia using a Lagrangian atmospheric transport model. For the first time, we use a recently developed feature that calculates deposition in backward (so-called retroplume) simulations allowing estimation of the specific locations of sources that contribute to the deposited mass
Incommensurability and edge states in the one-dimensional S=1 bilinear-biquadratic model
Commensurate-incommensurate change on the one-dimensional S=1
bilinear-biquadratic model () is examined. The gapped
Haldane phase has two subphases (the commensurate Haldane subphase and the
incommensurate Haldane subphase) and the commensurate-incommensurate change
point (the Affleck-Kennedy-Lieb-Tasaki point, ). There have been
two different analytical predictions about the static structure factor in the
neighborhood of this point. By using the S{\o}rensen-Affleck prescription,
these static structure factors are related to the Green functions, and also to
the energy gap behaviors. Numerical calculations support one of the
predictions. Accordingly, the commensurate-incommensurate change is recognized
as a motion of a pair of poles in the complex plane.Comment: 29 pages, 15 figure
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