978 research outputs found
The sh Lie structure of Poisson brackets in field theory
A general construction of an sh Lie algebra from a homological resolution of
a Lie algebra is given. It is applied to the space of local functionals
equipped with a Poisson bracket, induced by a bracket for local functions along
the lines suggested by Gel'fand, Dickey and Dorfman. In this way, higher order
maps are constructed which combine to form an sh Lie algebra on the graded
differential algebra of horizontal forms. The same construction applies for
graded brackets in field theory such as the Batalin-Fradkin-Vilkovisky bracket
of the Hamiltonian BRST theory or the Batalin-Vilkovisky antibracket.Comment: 24 pages Latex fil
Algebra Structures on Hom(C,L)
We consider the space of linear maps from a coassociative coalgebra C into a
Lie algebra L. Unless C has a cocommutative coproduct, the usual symmetry
properties of the induced bracket on Hom(C,L) fail to hold. We define the
concept of twisted domain (TD) algebras in order to recover the symmetries and
also construct a modified Chevalley-Eilenberg complex in order to define the
cohomology of such algebras
The Dynamical State of Barnard 68: A Thermally Supported, Pulsating Dark Cloud
We report sensitive, high resolution molecular-line observations of the dark
cloud Barnard 68 obtained with the IRAM 30-m telescope. We analyze
spectral-line observations of C18O, CS(2--1), C34S(2--1), and N2H+(1--0) in
order to investigate the kinematics and dynamical state of the cloud. We find
extremely narrow linewidths in the central regions of the cloud. These narrow
lines are consistent with thermally broadened profiles for the measured gas
temperature of 10.5 K. We determine the thermal pressure to be a factor 4 -- 5
times greater than the non-thermal (turbulent) pressure in the central regions
of the cloud, indicating that thermal pressure is the primary source of support
against gravity in this cloud. This confirms the inference of a thermally
supported cloud drawn previously from deep infrared extinction measurements.
The rotational kinetic energy is found to be only a few percent of the
gravitational potential energy, indicating that the contribution of rotation to
the overall stability of the cloud is insignificant. Finally, our observations
show that CS line is optically thick and self-reversed across nearly the entire
projected surface of the cloud. The shapes of the self-reversed profiles are
asymmetric and are found to vary across the cloud in such a manner that the
presence of both inward and outward motions are observed within the cloud.
Moreover, these motions appear to be globally organized in a clear and
systematic alternating spatial pattern which is suggestive of a small
amplitude, non-radial oscillation or pulsation of the outer layers of the cloud
about an equilibrium configuration.Comment: To appear in the Astrophysical Journal; 23 pages, 8 figures;
Manuscript and higher resolution images can be obtained at
http://cfa-www.harvard.edu/~ebergin/pubs_html/b68_vel.htm
Deformations of coisotropic submanifolds for fibrewise entire Poisson structures
We show that deformations of a coisotropic submanifold inside a fibrewise
entire Poisson manifold are controlled by the -algebra introduced by
Oh-Park (for symplectic manifolds) and Cattaneo-Felder. In the symplectic case,
we recover results previously obtained by Oh-Park. Moreover we consider the
extended deformation problem and prove its obstructedness
NGC 2362: a Template for Early Stellar Evolution
We present UBVRI photometry for the young open cluster NGC 2362. From
analysis of the appropriate color-color and color-magnitude diagrams we derive
the fundamental parameters of the NGC 2362 cluster to be: age = 5 (+1-2) Myr,
distance = 1480 pc, E(B-V)=0.10 mag. The cluster age was independently
determined for both high mass (2.1 - 36Msun) and low mass (0.7 - 1.2Msun) stars
with excellent agreement between the ages derived using post-main sequence and
pre-main sequence evolutionary tracks for the high and low mass stars
respectively. Analysis of this cluster's color-magnitude diagram reveals a well
defined pre-main sequence (covering DeltaV ~ 9 magnitudes in V and extending
from early A stars to near the hydrogen burning limit) which makes this cluster
an ideal laboratory for pre-main sequence evolution studies.Comment: 9 pages, 3 figures, to be published in ApJ
Non-Commutative Batalin-Vilkovisky Algebras, Homotopy Lie Algebras and the Courant Bracket
We consider two different constructions of higher brackets. First, based on a
Grassmann-odd, nilpotent \Delta operator, we define a non-commutative
generalization of the higher Koszul brackets, which are used in a generalized
Batalin-Vilkovisky algebra, and we show that they form a homotopy Lie algebra.
Secondly, we investigate higher, so-called derived brackets built from
symmetrized, nested Lie brackets with a fixed nilpotent Lie algebra element Q.
We find the most general Jacobi-like identity that such a hierarchy satisfies.
The numerical coefficients in front of each term in these generalized Jacobi
identities are related to the Bernoulli numbers. We suggest that the definition
of a homotopy Lie algebra should be enlarged to accommodate this important
case. Finally, we consider the Courant bracket as an example of a derived
bracket. We extend it to the "big bracket" of exterior forms and multi-vectors,
and give closed formulas for the higher Courant brackets.Comment: 42 pages, LaTeX. v2: Added remarks in Section 5. v3: Added further
explanation. v4: Minor adjustments. v5: Section 5 completely rewritten to
include covariant construction. v6: Minor adjustments. v7: Added references
and explanation to Section
The Dynamical State fo the Starless Dense Core FeSt 1-457: A Pulsating Globule?
High resolution molecular line observations of CS, HCO+, C18O and N2H+ were
obtained toward the starless globule FeSt 1-457 in order to investigate its
kinematics and chemistry. The HCO+ and CS spectra show clear self-reversed and
asymmetric profiles across the face of the globule. The sense of the observed
asymmetry is indicative of the global presence of expansion motions in the
outer layers of the globule. These motions appear to be subsonic and
significantly below the escape velocity of the globule. Comparison of our
observations with near-infrared extinction data indicate that the globule is
gravitationally bound. Taken together these considerations lead us to suggest
that the observed expansion has its origin in an oscillatory motion of the
outer layers of the globule which itself is likely in a quasi-stable state near
hydrostatic equilibrium. Analysis of the observed linewidths of CO and N2H+
confirm that thermal pressure is the dominant component of the cloud's internal
support. A simple calculation suggests that the dominant mode of pulsation
would be an l = 2 mode with a period of 0.3 Myr. Deformation of the globule due
to the large amplitude l = 2 oscillation may be responsible for the
double-peaked structure of the core detected in high resolution extinction
maps. Detailed comparison of the molecular-line observations and extinction
data provides evidence for significant depletion of C18O and perhaps HCO+ while
N2H+ may be undepleted to a cloud depth of about 40 magnitudes of visual
extinction.Comment: to appear in ApJ vol 665 20 August 2007
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