238 research outputs found
Decoherence Strength of Multiple Non-Markovian Environments
It is known that one can characterize the decoherence strength of a Markovian
environment by the product of its temperature and induced damping, and order
the decoherence strength of multiple environments by this quantity. We show
that for non-Markovian environments in the weak coupling regime there also
exists a natural (albeit partial) ordering of environment-induced
irreversibility within a perturbative treatment. This measure can be applied to
both low-temperature and non-equilibrium environments.Comment: 6 pages, 1 figure, v3 included figure, appendix, and clarification of
result
Electromagnetic Response of Layered Superconductors with Broken Lattice Inversion Symmetry
We investigate the macroscopic effects of charge density waves (CDW) and
superconductivity in layered superconducting systems with broken lattice
inversion symmetry (allowing for piezoelectricity) such as two dimensional (2D)
transition metal dichalcogenides (TMD). We work with the low temperature time
dependent Ginzburg-Landau theory and study the coupling of lattice distortions
and low energy CDW collective modes to the superconducting order parameter in
the presence of electromagnetic fields. We show that superconductivity and
piezoelectricity can coexist in these singular metals. Furthermore, our study
indicates the nature of the quantum phase transition between a commensurate CDW
phase and the stripe phase that has been observed as a function of applied
pressure.Comment: 9 pages, 1 figure. Final version. Accepted in Phys.Rev.
Exact analytical solutions to the master equation of quantum Brownian motion for a general environment
We revisit the model of a quantum Brownian oscillator linearly coupled to an
environment of quantum oscillators at finite temperature. By introducing a
compact and particularly well-suited formulation, we give a rather quick and
direct derivation of the master equation and its solutions for general spectral
functions and arbitrary temperatures. The flexibility of our approach allows
for an immediate generalization to cases with an external force and with an
arbitrary number of Brownian oscillators. More importantly, we point out an
important mathematical subtlety concerning boundary-value problems for
integro-differential equations which led to incorrect master equation
coefficients and impacts on the description of nonlocal dissipation effects in
all earlier derivations. Furthermore, we provide explicit, exact analytical
results for the master equation coefficients and its solutions in a wide
variety of cases, including ohmic, sub-ohmic and supra-ohmic environments with
a finite cut-off.Comment: 37 pages (26 + appendices), 14 figures; this paper is an evolution of
arXiv:0705.2766v1, but contains far more general and significant results; v2
minor changes, double column, improved Appendix
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Use of Z-pinch radiation sources for high-pressure shock wave studies
The authors are developing a new shock wave diagnostic using Z pinch sources for high-pressure equation of state (EOS) measurements. Specifically, they are employing VISAR interferometry to measure the particle velocity of shocked materials and fiber optic probes to measure the shock speed. Combination of these measurements will allow absolute EOS data with Z accelerators. This report is a progress report on the development of this new approach to EOS measurements; however, preliminary data obtained with the diagnostics are encouraging. With further development of Z pinch sources, it is envisioned that a variety of EOS and constitutive property measurements can be made. Time-resolved wave profile measurements will then provide a variety of EOS and material property data, such as isentropic EOS, initial compressive strength and shock-induced compressive strength, dynamic tensile strength, kinetics of phase transitions, and surface stability studies
The impact of boundary layer height on air pollution concentrations in London â early results from the ClearfLo project.
The ClearfLo projects aims to understand the processes generating pollutants like ozone, NOx and particulate
matter and their interaction with the urban atmospheric boundary layer. ClearfLo (www.clearflo.ac.uk) is a
large multi-institution NERC-funded project that is establishing integrated measurements of the meteorology,
composition and particulate loading of Londonâs urban atmosphere, complemented by an ambitious modeling
programme.
The project established a new long-term measurement infrastructure in London encompassing measurement
capabilities at street level and at elevated sites. These measurements were accompanied by high resolution mod-
eling with the UK Met Office Unified model and WRF. This combined measuring/modelling approach enables
us to identify the seasonal cycle in the meteorology and composition, together with the controlling processes.
Two intensive observation periods in January/February 2012 and during the Olympics in summer 2012 measured
Londonâs atmosphere with higher level of detail. Data from these IOPs will enable us (i) to determine the vertical
structure and evolution of the urban atmosphere (ii) to determine the chemical controls on ozone production,
particularly the role of biogenic emissions and (iii) to determine the processes controlling the evolution of the size,distribution and composition of particulate matter.
We present results from the wintertime IOP in London focusing on a wintertime pollution episode during
January 2012. We compare measured concentrations from top of BT Tower in central London with rural background measurements and determine the processes leading to the urban increment in pollutant concentrations.
Therefore, we combine high-resolution simulations with the Met Office Unified Model for London and mixing
layer heights derived from lidar measurements with air quality measurements in central London in order to
quantify the role the boundary layer depth plays for Londonâs concentrations
Colossal dielectric constants in transition-metal oxides
Many transition-metal oxides show very large ("colossal") magnitudes of the
dielectric constant and thus have immense potential for applications in modern
microelectronics and for the development of new capacitance-based
energy-storage devices. In the present work, we thoroughly discuss the
mechanisms that can lead to colossal values of the dielectric constant,
especially emphasising effects generated by external and internal interfaces,
including electronic phase separation. In addition, we provide a detailed
overview and discussion of the dielectric properties of CaCu3Ti4O12 and related
systems, which is today's most investigated material with colossal dielectric
constant. Also a variety of further transition-metal oxides with large
dielectric constants are treated in detail, among them the system La2-xSrxNiO4
where electronic phase separation may play a role in the generation of a
colossal dielectric constant.Comment: 31 pages, 18 figures, submitted to Eur. Phys. J. for publication in
the Special Topics volume "Cooperative Phenomena in Solids: Metal-Insulator
Transitions and Ordering of Microscopic Degrees of Freedom
Heavy quarkonium: progress, puzzles, and opportunities
A golden age for heavy quarkonium physics dawned a decade ago, initiated by
the confluence of exciting advances in quantum chromodynamics (QCD) and an
explosion of related experimental activity. The early years of this period were
chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in
2004, which presented a comprehensive review of the status of the field at that
time and provided specific recommendations for further progress. However, the
broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles
could only be partially anticipated. Since the release of the YR, the BESII
program concluded only to give birth to BESIII; the -factories and CLEO-c
flourished; quarkonium production and polarization measurements at HERA and the
Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the
deconfinement regime. All these experiments leave legacies of quality,
precision, and unsolved mysteries for quarkonium physics, and therefore beg for
continuing investigations. The plethora of newly-found quarkonium-like states
unleashed a flood of theoretical investigations into new forms of matter such
as quark-gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the
spectroscopy, decays, production, and in-medium behavior of c\bar{c}, b\bar{b},
and b\bar{c} bound states have been shown to validate some theoretical
approaches to QCD and highlight lack of quantitative success for others. The
intriguing details of quarkonium suppression in heavy-ion collisions that have
emerged from RHIC have elevated the importance of separating hot- and
cold-nuclear-matter effects in quark-gluon plasma studies. This review
systematically addresses all these matters and concludes by prioritizing
directions for ongoing and future efforts.Comment: 182 pages, 112 figures. Editors: N. Brambilla, S. Eidelman, B. K.
Heltsley, R. Vogt. Section Coordinators: G. T. Bodwin, E. Eichten, A. D.
Frawley, A. B. Meyer, R. E. Mitchell, V. Papadimitriou, P. Petreczky, A. A.
Petrov, P. Robbe, A. Vair
Determination of color-octet matrix elements from e^+e- process at low energies
We present an analysis of the preliminary experimental data of direct j/psi
production in e^e- process at low energies. We find that the color-octet
contributions are crucially important to the cross section at this energy
region, and their inclusion produces a good description of the data. By fitting
to the data, we extract the individual values of two color-octet matrix
elements: \approx 1.1\times 10^{-2} GeV^3, <{\cal
O}_8^{\psi}(^3P_0)> m_c^2\approx 7.4\times 10^{-3}GeV^3. We discuss the allowed
range of the two matrix elements constrained by the theoretical uncertainties.
We find that is poorly determined because it is
sensitive to the variation of the choice of m_c, \alpha_s and <{\cal
O}_1^{\psi}(^3S_1)>. However m_c^2 is quite stable
(about (6-9)\times 10^{-3}GeV^3) when the parameters vary in reasonable ranges.
The uncertainties due to large experimental errors are also discussed.Comment: 13 page, RevTex, 2 figures in postscript. To appear in Phys. Rev.
Entanglement generation and transfer between remote atomic qubits interacting with squeezed field
A pair of two level atoms A1A2, prepared either in a separable state or in an
entangled state, interacts with a single mode of two mode squeezed cavity field
while a third atomic qubit B interacts with the second mode of the squeezed
field in a remote cavity. We analyze, numerically, the generation, sudden death
and revival of three qubit entanglement as a function of initial entanglement
of qubits A1A2 and degree of squeezing of electromagnetic field. Global
negativity of partially transposed state operator is used to quantify the
entanglement of three atom state. It is found that the initial entanglement of
two mode field as well as that of the pair A1A2, both, contribute to three atom
entanglement. A maximally entangled single excitation Bell pair in first cavity
and two mode field with squeeze parameter s=0.64 are the initial conditions
that optimize the peak value of three qubit mixed state entanglement. A smaller
value of s=0.4 under similar conditions is found to generate a three qubit
mixed state with comparable entanglement dynamics free from entanglement sudden
death.Comment: 14 pages, 7 figures, sections III and IV merged with section II and
analytic expressions moved to Appendices A and B. Figures improved and
corrected typo
Kerb and urban increment of highly time-resolved trace elements in PMââ, PMâÌŁâ and PMâÌŁâ winter aerosol in London during ClearfLo 2012
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