47,375 research outputs found
Dissipative superfluid mass flux through solid 4He
The thermo-mechanical effect in superfluid helium is used to create an
initial chemical potential difference, , across a solid He
sample. This causes a flow of helium atoms from one reservoir
filled with superfluid helium, through a sample cell filled with solid helium,
to another superfluid-filled reservoir until chemical potential equilibrium is
restored. The solid helium sample is separated from each of the reservoirs by
Vycor rods that allow only the superfluid component to flow. With an improved
technique, measurements of the flow, , at several fixed solid helium
temperatures, , have been made as function of in the pressure
range 25.5 - 26.1 bar. And, measurements of have been made as a function of
temperature in the range ~mK for several fixed values of . The temperature dependence of the flow above ~mK shows a reduction
of the flux with an increase in temperature that is well described by . The non-linear functional dependence , with independent of temperature but dependent on pressure,
documents in some detail the dissipative nature of the flow and suggests that
this system demonstrates Luttinger liquid-like one-dimensional behavior. The
mechanism that causes this flow behavior is not certain, but is consistent with
superflow on the cores of edge dislocations.Comment: 11 pages, 14 figure
Mass flux characteristics in solid 4He for T> 100 mK: Evidence for Bosonic Luttinger Liquid behavior
At pressure 25.7 bar the flux, , carried by solid \4he for
100 mK depends on the net chemical potential difference between two reservoirs
in series with the solid, , and obeys ,
where is independent of temperature. At fixed the
temperature dependence of the flux, , can be adequately represented by , K, for K. A
single function fits all of the available
data sets in the range 25.6 - 25.8 bar reasonably well. We suggest that the
mass flux in solid \4he for mK may have a Luttinger liquid-like
behavior in this bosonic system.Comment: 4 pages, 5 figure
On gauge-invariant Green function in 2+1 dimensional QED
Both the gauge-invariant fermion Green function and gauge-dependent
conventional Green function in dimensional QED are studied in the large
limit. In temporal gauge, the infra-red divergence of gauge-dependent
Green function is found to be regulariable, the anomalous dimension is found to
be . This anomalous dimension was argued to be
the same as that of gauge-invariant Green function. However, in Coulomb gauge,
the infra-red divergence of the gauge-dependent Green function is found to be
un-regulariable, anomalous dimension is even not defined, but the infra-red
divergence is shown to be cancelled in any gauge-invariant physical quantities.
The gauge-invariant Green function is also studied directly in Lorentz
covariant gauge and the anomalous dimension is found to be the same as that
calculated in temporal gauge.Comment: 8 pages, 6 figures, to appear in Phys. Rev.
Market Equilibrium with Transaction Costs
Identical products being sold at different prices in different locations is a
common phenomenon. Price differences might occur due to various reasons such as
shipping costs, trade restrictions and price discrimination. To model such
scenarios, we supplement the classical Fisher model of a market by introducing
{\em transaction costs}. For every buyer and every good , there is a
transaction cost of \cij; if the price of good is , then the cost to
the buyer {\em per unit} of is p_j + \cij. This allows the same good
to be sold at different (effective) prices to different buyers.
We provide a combinatorial algorithm that computes -approximate
equilibrium prices and allocations in
operations -
where is the number goods, is the number of buyers and is the sum
of the budgets of all the buyers
- …