1,606 research outputs found
On the Bartnik extension problem for the static vacuum Einstein equations
We develop a framework for understanding the existence of asymptotically flat
solutions to the static vacuum Einstein equations with prescribed boundary data
consisting of the induced metric and mean curvature on a 2-sphere. A partial
existence result is obtained, giving a partial resolution of a conjecture of
Bartnik on such static vacuum extensions. The existence and uniqueness of such
extensions is closely related to Bartnik's definition of quasi-local mass.Comment: 33 pages, 1 figure. Minor revision of v2. Final version, to appear in
Class. Quantum Gravit
Bounds for moments of -torsion in class groups
Fix a number field , integers , and a prime . For all
, we prove strong unconditional upper bounds on the -th moment of
-torsion in the ideal class groups of degree extensions of and of
degree -extensions of , improving upon results of Ellenberg, Pierce
and Wood as well as GRH-conditional results of Frei and Widmer. For large ,
our results are comparable with work of Heath-Brown and Pierce for imaginary
quadratic extensions of . When , our results are new even for
the family of all quadratic extensions of , leading to an improved
upper bound for the count of degree -extensions over
(where is the dihedral group of order ).Comment: 12 page
On contact numbers of totally separable unit sphere packings
Contact numbers are natural extensions of kissing numbers. In this paper we
give estimates for the number of contacts in a totally separable packing of n
unit balls in Euclidean d-space for all n>1 and d>1.Comment: 11 page
State-Insensitive Cooling and Trapping of Single Atoms in an Optical Cavity
Single Cesium atoms are cooled and trapped inside a small optical cavity by
way of a novel far-off-resonance dipole-force trap (FORT), with observed
lifetimes of 2 to 3 seconds. Trapped atoms are observed continuously via
transmission of a strongly coupled probe beam, with individual events lasting ~
1 s. The loss of successive atoms from the trap N = 3 -> 2 -> 1 -> 0 is thereby
monitored in real time. Trapping, cooling, and interactions with strong
coupling are enabled by the FORT potential, for which the center-of-mass motion
is only weakly dependent on the atom's internal state.Comment: 5 pages, 4 figures Revised version to appear in Phys. Rev. Let
Teichm\"uller's problem in space
Quasiconformal homeomorphisms of the whole space Rn, onto itself normalized
at one or two points are studied. In particular, the stability theory, the case
when the maximal dilatation tends to 1, is in the focus. Our main result
provides a spatial analogue of a classical result due to Teichm\"uller. Unlike
Teichm\"uller's result, our bounds are explicit. Explicit bounds are based on
two sharp well-known distortion results: the quasiconformal Schwarz lemma and
the bound for linear dilatation. Moreover, Bernoulli type inequalities and
asymptotically sharp bounds for special functions involving complete elliptic
integrals are applied to simplify the computations. Finally, we discuss the
behavior of the quasihyperbolic metric under quasiconformal maps and prove a
sharp result for quasiconformal maps of R^n \ {0} onto itself.Comment: 25 pages, 2 figure
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