3,117 research outputs found
Loop Expansion in Light-Cone Field Theory
A loop expansion is implemented based on the path integral quantization of
the light-cone field theory in 1+1 dimensions. The effective potential
as a function of the zero-mode field is calculated up to two loop
order and its derivative with respect to is used to determine the
vacuum expectation value of the field . The critical coupling constant at
the spontaneous symmetry breakdown is consistent with that obtained in the
ordinary instant-form field theory. The critical exponents which describe the
behavior of the susceptibility and the vacuum expectation value of near
the critical point are evaluated from the effective potential. The one loop
diagrams for the connected Green's function are calculated in momentum space.
The relevant equal-time correlation function is shown to be closely related.Comment: 12 pages, plain Tex, 1 table, 3 figures available from
[email protected] , accepted by Phys. Rev.
Constant-Competitive Prior-Free Auction with Ordered Bidders
A central problem in Microeconomics is to design auctions with good revenue
properties. In this setting, the bidders' valuations for the items are private
knowledge, but they are drawn from publicly known prior distributions. The goal
is to find a truthful auction (no bidder can gain in utility by misreporting
her valuation) that maximizes the expected revenue.
Naturally, the optimal-auction is sensitive to the prior distributions. An
intriguing question is to design a truthful auction that is oblivious to these
priors, and yet manages to get a constant factor of the optimal revenue. Such
auctions are called prior-free.
Goldberg et al. presented a constant-approximate prior-free auction when
there are identical copies of an item available in unlimited supply, bidders
are unit-demand, and their valuations are drawn from i.i.d. distributions. The
recent work of Leonardi et al. [STOC 2012] generalized this problem to non
i.i.d. bidders, assuming that the auctioneer knows the ordering of their
reserve prices. Leonardi et al. proposed a prior-free auction that achieves a
approximation. We improve upon this result, by giving the first
prior-free auction with constant approximation guarantee.Comment: The same result has been obtained independently by E. Koutsoupias, S.
Leonardi and T. Roughgarde
Field Induced Jet Micro-EDM
Electrical discharge machining (EDM) is of the potential of
micro/nano meter scale machining capability. However,
electrode wear in micro-EDM significantly deteriorates the
machining accuracy, thus, it needs to be compensated in
process. To solve this problem, a novel micromachining
method, namely field induced jet micro-EDM, is proposed in
this paper, in which the electrical field induced jet is used as
the micro tool electrode. A series of experiments were carried
out to investigate the feasibility of proposed method. Due to
the electrolyte can be supplied automatically by the capillary
effect and the electrostatic field, it is not necessary to use
pump or valves. The problem of electrode wear does not exist
at all in the machining process because of the field induced jet
will be generated periodically. It is also found that the workpiece
material can be effectively removed with a crater size of
about 2 micrometer in diameter. The preliminary experimental results
verified that the field induced jet micro-EDM is an effective
micromachining method
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