123 research outputs found
Compressive Earth Observatory: An Insight from AIRS/AMSU Retrievals
We demonstrate that the global fields of temperature, humidity and
geopotential heights admit a nearly sparse representation in the wavelet
domain, offering a viable path forward to explore new paradigms of
sparsity-promoting data assimilation and compressive recovery of land
surface-atmospheric states from space. We illustrate this idea using retrieval
products of the Atmospheric Infrared Sounder (AIRS) and Advanced Microwave
Sounding Unit (AMSU) on board the Aqua satellite. The results reveal that the
sparsity of the fields of temperature is relatively pressure-independent while
atmospheric humidity and geopotential heights are typically sparser at lower
and higher pressure levels, respectively. We provide evidence that these
land-atmospheric states can be accurately estimated using a small set of
measurements by taking advantage of their sparsity prior.Comment: 12 pages, 8 figures, 1 tabl
Holographic Magnetic Star
A warm fermionic AdS star under a homogeneous magnetic field is explored. We
obtain the relativistic Landau levels by using Dirac equation and use the
Tolman-Oppenheimer-Volkoff (TOV) equation to study the physical profiles of the
star. Bulk properties such as sound speed, adiabatic index, and entropy density
within the star are calculated analytically and numerically. Bulk temperature
increases the mass limit of the AdS star but external magnetic field has the
opposite effect. The results are partially interpreted in terms of the
pre-thermalization process of the gauge matter at the AdS boundary after the
mass injection. The entropy density is found to demonstrate similar temperature
dependence as the magnetic black brane in the AdS in certain limits regardless
of the different nature of the bulk and Hawking temperatures. Total entropy of
the AdS star is also found to be an increasing function of the bulk temperature
and a decreasing function of the magnetic field, similar behaviour to the mass
limit. Since both total entropy and mass limit are global quantities, they
could provide some hints to the value of entropy and energy of the dual gauge
matter before and during the thermalization.Comment: 39 pages, 14 figures, 1 table, comments and references added, to
appear in JHE
Holographic Dark Information Energy
Landauer's principle and the Holographic principle are used to derive the
holographic information energy contribution to the Universe. Information energy
density has increased with star formation until sufficient to start
accelerating the expansion of the universe. The resulting reduction in the rate
of star formation due to the accelerated expansion may provide a feedback that
limits the information energy density to a constant level. The characteristics
of the universe's holographic information energy then closely match those
required to explain dark energy and also answer the cosmic coincidence problem.
Furthermore the era of acceleration will be clearly limited in time.Comment: 12 pages, 2 figure
Effective action for the order parameter of the deconfinement transition of Yang-Mills theories
The effective action for the Polyakov loop serving as an order parameter for
deconfinement is obtained in one-loop approximation to second order in a
derivative expansion. The calculation is performed in dimensions,
mostly referring to the gauge group SU(2). The resulting effective action is
only capable of describing a deconfinement phase transition for
. Since, particularly in , the system is
strongly governed by infrared effects, it is demonstrated that an additional
infrared scale such as an effective gluon mass can change the physical
properties of the system drastically, leading to a model with a deconfinement
phase transition.Comment: 23 pages, 4 figures, minor improvements, version to appear in PR
Path-integral quantization of Galilean Fermi fields
The Galilei-covariant fermionic field theories are quantized by using the
path-integral method and five-dimensional Lorentz-like covariant expressions of
non-relativistic field equations. Firstly, we review the five-dimensional
approach to the Galilean Dirac equation, which leads to the Levy-Leblond
equations, and define the Galilean generating functional and Green's functions
for positive- and negative-energy/mass solutions. Then, as an example of
interactions, we consider the quartic self-interacting potential , and we derive expressions for the 2- and 4-point
Green's functions. Our results are compatible with those found in the
literature on non-relativistic many-body systems. The extended manifold allows
for compact expressions of the contributions in space-time. This is
particularly apparent when we represent the results with diagrams in the
extended manifold, since they usually encompass more diagrams in
Galilean space-time.Comment: LATEX file, 27 pages, 8 figures; typos in the journal version are
removed, equation (1) in Introduction is correcte
On Charged Black Holes in Anti-de Sitter Space
We study the region inside the event horizon of charged black holes in five
dimensional asymptotically anti-de Sitter space, using as a probe two-sided
correlators which are dominated by spacelike geodesics penetrating the horizon.
The spacetimes we investigate include the Reissner-Nordstrom black hole and
perturbations thereof. The perturbed spacetimes can be found exactly, enabling
us to perform a local scan of the region between the inner and outer horizons.
Surprisingly, the two-sided correlators we calculate seem to be geometrically
protected from the instability of the inner horizon.Comment: 1+37 pages, 20 ps and eps figures, LaTeX. References added and
changes made to section
Lattice gauge theory with baryons at strong coupling
We study the effective Hamiltonian for strong-coupling lattice QCD in the
case of non-zero baryon density. In leading order the effective Hamiltonian is
a generalized antiferromagnet. For naive fermions, the symmetry is U(4N_f) and
the spins belong to a representation that depends on the local baryon number.
Next-nearest-neighbor (nnn) terms in the Hamiltonian break the symmetry to
U(N_f) x U(N_f). We transform the quantum problem to a Euclidean sigma model
which we analyze in a 1/N_c expansion. In the vacuum sector we recover
spontaneous breaking of chiral symmetry for the nearest-neighbor and nnn
theories. For non-zero baryon density we study the nearest-neighbor theory
only, and show that the pattern of spontaneous symmetry breaking depends on the
baryon density.Comment: 31 pages, 5 EPS figures. Corrected Eq. (6.1
Non-state actors in hybrid global climate governance: justice, legitimacy, and effectiveness in a post-Paris era
In this article, we outline the multifaceted roles played by non-state actors within the United Nations Framework Convention on Climate Change and place this within the wider landscape of global climate governance. In doing so, we look at both the formation and aftermath of the 2015 Paris Agreement. We argue that the Paris Agreement cements an architecture of hybrid multilateralism that enables and constrains non-state actor participation in global climate governance. We flesh out the constitutive features of hybrid multilateralism, enumerate the multiple positions non-state actors may employ under these conditions, and contend that non-state actors will play an increasingly important role in the post-Paris era. To substantiate these claims, we assess these shifts and ask how non-state actors may affect the legitimacy, justice, and effectiveness of the Paris Agreement
Phases and Residual Gauge Symmetries of Higgs Models
After elimination of the redundant variables, gauge theories may still
exhibit symmetries associated with the gauge fields. The role of these residual
gauge symmetries is discussed within the Abelian Higgs model and the
Georgi-Glashow model. In the different phases of these models, these symmetries
are realized differently. The characteristics of emergence and disappearance of
the symmetries are studied in detail and the implications for the dynamics in
Coulomb, Higgs, and confining phases are discussed.Comment: 30 pages, LaTeX with amsmath macros; updated to include minor
corrections in proof; email correspondence to J.W. Negele,
[email protected]
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