1,678 research outputs found
Strong CP Violation in External Magnetic Fields
We study the response of the QCD vacuum to an external magnetic field, in the
presence of strong CP violation. Using chiral perturbation theory and large N_c
expansion, we show that the external field would polarize quantum fluctuations
and induce an electric dipole moment of the vacuum, along the direction of the
magnetic field. We estimate the magnitude of this effect in different physical
scenarios. In particular, we find that the polarization induced by the magnetic
field of a magnetar could accelerate electric charges up to energies of the
order \theta 10^3 TeV. We also suggest a connection with the possible existence
of "hot-spots" on the surface of neutron stars.Comment: 4 pages, 1 figure. Major revision. Phenomenological analysis extende
Monetary policy as a source of uncertainty
This paper proposes a model in which control variations induce an increase in the uncertainty of the system. The aim of our paper is to provide a stochastic theoretical model that can be used to explain under which uncertainty conditions monetary policy rules should be less or more aggressive, or, simply, applied or not.
Remarkable symmetries in the Milky Way disk's magnetic field
Using a new, expanded compilation of extragalactic source Faraday rotation
measures (RM) we investigate the broad underlying magnetic structure of the
Galactic disk at latitudes over all longitudes ,
where our total number of RM's in this low-latitude range of the Galactic sky
is comparable to those in the combined Canadian Galactic Plane Survey(CGPS) at
and the Southern Galactic Plane (SGPS)
survey. We report newly revealed, remarkably coherent patterns of RM at
from to and RM()
features of unprecedented clarity that replicate in with opposite sign on
opposite sides of the Galactic center. They confirm a highly patterned
bisymmetric field structure toward the inner disc, an axisymmetic pattern
toward the outer disc, and a very close coupling between the CGPS/SGPS RM's at
("mid-plane") and our new RM's up to ("near-plane").
Our analysis also shows the approximate -height -- the vertical height of
the coherent component of the disc field above the Galactic disc's mid-plane --
to be kpc out to kpc from the Sun. This identifies the
approximate height of the transition layer to the halo field structure. We find
no RM sign change across the plane within in any
longitude range. The prevailing {\it disc} field pattern, and its striking
degree of large scale ordering confirm that our side of the Milky Way has a
very organized underlying magnetic structure, for which the inward spiral pitch
angle is at all up to in
the inner semicircle of Galactic longitudes. It decreases to
toward the anticentre.Comment: 7 pages, 5 figures, Version 3. Accepted 2011 for publication in
Publications of the Astronomical Society of Australia(PASA
Smearing of the 2D Kohn anomaly in a nonquantizing magnetic field: Implications for the interaction effects
Thermodynamic and transport characteristics of a clean two-dimensional
interacting electron gas are shown to be sensitive to the weak perpendicular
magnetic field even at temperatures much higher than the cyclotron energy, when
the quantum oscillations are completely washed out. We demonstrate this
sensitivity for two interaction-related characteristics: electron lifetime and
the tunnel density of states. The origin of the sensitivity is traced to the
field-induced smearing of the Kohn anomaly; this smearing is the result of
curving of the semiclassical electron trajectories in magnetic field.Comment: 4.5 pages, 3 figures, published versio
Heap Reference Analysis Using Access Graphs
Despite significant progress in the theory and practice of program analysis,
analysing properties of heap data has not reached the same level of maturity as
the analysis of static and stack data. The spatial and temporal structure of
stack and static data is well understood while that of heap data seems
arbitrary and is unbounded. We devise bounded representations which summarize
properties of the heap data. This summarization is based on the structure of
the program which manipulates the heap. The resulting summary representations
are certain kinds of graphs called access graphs. The boundedness of these
representations and the monotonicity of the operations to manipulate them make
it possible to compute them through data flow analysis.
An important application which benefits from heap reference analysis is
garbage collection, where currently liveness is conservatively approximated by
reachability from program variables. As a consequence, current garbage
collectors leave a lot of garbage uncollected, a fact which has been confirmed
by several empirical studies. We propose the first ever end-to-end static
analysis to distinguish live objects from reachable objects. We use this
information to make dead objects unreachable by modifying the program. This
application is interesting because it requires discovering data flow
information representing complex semantics. In particular, we discover four
properties of heap data: liveness, aliasing, availability, and anticipability.
Together, they cover all combinations of directions of analysis (i.e. forward
and backward) and confluence of information (i.e. union and intersection). Our
analysis can also be used for plugging memory leaks in C/C++ languages.Comment: Accepted for printing by ACM TOPLAS. This version incorporates
referees' comment
A Number-Theoretic Error-Correcting Code
In this paper we describe a new error-correcting code (ECC) inspired by the
Naccache-Stern cryptosystem. While by far less efficient than Turbo codes, the
proposed ECC happens to be more efficient than some established ECCs for
certain sets of parameters. The new ECC adds an appendix to the message. The
appendix is the modular product of small primes representing the message bits.
The receiver recomputes the product and detects transmission errors using
modular division and lattice reduction
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