92,195 research outputs found
Gaussian Effective Potential and the Coleman's normal-ordering Prescription : the Functional Integral Formalism
For a class of system, the potential of whose Bosonic Hamiltonian has a
Fourier representation in the sense of tempered distributions, we calculate the
Gaussian effective potential within the framework of functional integral
formalism. We show that the Coleman's normal-ordering prescription can be
formally generalized to the functional integral formalism.Comment: 6 pages, revtex; With derivation details and an example added. To
appear in J. Phys.
Alternative approach to all-angle negative refraction in two-dimensional photonic crystals
We show that with an appropriate surface modification, a slab of photonic
crystal can be made to allow wave transmission within the band gap.
Furthermore, negative refraction and all-angle-negative-refraction (AANR) can
be achieved by this surface modification in frequency windows that were not
realized before in two-dimensional photonic crystals [C. Luo et al, Phys. Rev.
B 65, 201104 (2002)]. This approach to AANR leads to new applications in flat
lens imaging. Previous flat lens using photonic crystals requires object-image
distance u+v less than or equal to the lens thickness d, u+v d. Our approach
can be used to design flat lens with u+v=sd with s>>1, thus being able to image
large and/or far away objects. Our results are confirmed by FDTD simulations.Comment: 5 pages, 9 eps figs in RevTex forma
Process migration in UNIX environments
To support process migration in UNIX environments, the main problem is how to encapsulate the location dependent features of the system in such a way that a host independent virtual environment is maintained by the migration handlers on the behalf of each migrated process. An object-oriented approach is used to describe the interaction between a process and its environment. More specifically, environmental objects were introduced in UNIX systems to carry out the user-environment interaction. The implementation of the migration handlers is based on both the state consistency criterion and the property consistency criterion
Correctness criteria for process migration
Two correctness criteria, the state consistency criterion and the property consistency criterion for process migration are discussed. The state machine approach is used to model the interactions between a user process and its environment. These criteria are defined in terms of the model. The idea of environment view was introduced to distinguish what a user process observes about its environment from what its environment state really is and argue that a consistent view of the environment must be maintained for every migrating process
Radial Trends in IMF-Sensitive Absorption Features in Two Early-Type Galaxies: Evidence for Abundance-Driven Gradients
Samples of early-type galaxies show a correlation between stellar velocity
dispersion and the stellar initial mass function (IMF) as inferred from
gravity-sensitive absorption lines in the galaxies' central regions. To search
for spatial variations in the IMF, we have observed two early-type galaxies
with Keck/LRIS and measured radial gradients in the strengths of absorption
features from 4000-5500 \AA and 8000-10,000 \AA. We present spatially
resolved measurements of the dwarf-sensitive spectral indices NaI (8190 \AA)
and Wing-Ford FeH (9915 \AA), as well as indices for species of H, C, CN,
Mg, Ca, TiO, and Fe. Our measurements show a metallicity gradient in both
objects, and Mg/Fe consistent with a shallow gradient in \alpha-enhancement,
matching widely observed trends for massive early-type galaxies. The NaI index
and the CN index at 4160 \AA exhibit significantly steeper gradients,
with a break at ( pc). Inside this radius
NaI strength increases sharply toward the galaxy center, consistent with a
rapid central rise in [Na/Fe]. In contrast, the ratio of FeH to Fe index
strength decreases toward the galaxy center. This behavior cannot be reproduced
by a steepening IMF inside if the IMF is a single power law.
While gradients in the mass function above may occur,
exceptional care is required to disentangle these IMF variations from the
extreme variations in individual element abundances near the galaxies' centers.Comment: Accepted for publication in ApJ. Updates from v1 include an expanded
comparison of measured index strengths to SPS models. 20 page body + 7 page
appendix + references. Includes 25 figure
The (1+1)-dimensional Massive sine-Gordon Field Theory and the Gaussian Wave-functional Approach
The ground, one- and two-particle states of the (1+1)-dimensional massive
sine-Gordon field theory are investigated within the framework of the Gaussian
wave-functional approach. We demonstrate that for a certain region of the
model-parameter space, the vacuum of the field system is asymmetrical.
Furthermore, it is shown that two-particle bound state can exist upon the
asymmetric vacuum for a part of the aforementioned region. Besides, for the
bosonic equivalent to the massive Schwinger model, the masses of the one boson
and two-boson bound states agree with the recent second-order results of a
fermion-mass perturbation calculation when the fermion mass is small.Comment: Latex, 11 pages, 8 figures (EPS files
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