1,931 research outputs found
Efficiency and marginal cost pricing in dynamic competitive markets with friction
This paper examines a dynamic general equilibrium model with supply friction. With or without friction, the competitive equilibrium is efficient. Without friction, the market price is completely determined by the marginal production cost. If friction is present, no matter how small, then the market price fluctuates between zero and the "choke-up" price, without any tendency to converge to the marginal production cost, exhibiting considerable volatility. The distribution of the gains from trading in an efficient allocation may be skewed in favor of the supplier, although every player in the market is a price taker.Dynamic general equilibrium model with supply friction, choke-up price, marginal production cost, welfare theorems
MLE-guided parameter search for task loss minimization in neural sequence modeling
Neural autoregressive sequence models are used to generate sequences in a
variety of natural language processing (NLP) tasks, where they are evaluated
according to sequence-level task losses. These models are typically trained
with maximum likelihood estimation, which ignores the task loss, yet
empirically performs well as a surrogate objective. Typical approaches to
directly optimizing the task loss such as policy gradient and minimum risk
training are based around sampling in the sequence space to obtain candidate
update directions that are scored based on the loss of a single sequence. In
this paper, we develop an alternative method based on random search in the
parameter space that leverages access to the maximum likelihood gradient. We
propose maximum likelihood guided parameter search (MGS), which samples from a
distribution over update directions that is a mixture of random search around
the current parameters and around the maximum likelihood gradient, with each
direction weighted by its improvement in the task loss. MGS shifts sampling to
the parameter space, and scores candidates using losses that are pooled from
multiple sequences. Our experiments show that MGS is capable of optimizing
sequence-level losses, with substantial reductions in repetition and
non-termination in sequence completion, and similar improvements to those of
minimum risk training in machine translation
Hadronic production calculated in the NRQCD factorization formalism
The NRQCD factorization formalism of Bodwin, Braaten, and Lepage prescribes
how to write quarkonium production rates as a sum of products of short-distance
coefficients times non-perturbative long-distance NRQCD matrix elements. We
present, in the true spirit of the factorization formalism, a detailed
calculation of the inclusive cross section for hadronic production. We
find that in addition to the well known {\it color-singlet} production
mechanisms, there are equally important mechanisms in which the pair
that forms the is initially produced in a {\it color-octet} state, in
either a , , or angular-momentum
configuration. In our presentation, we emphasize the ``matching'' procedure,
which %is the method that allows us to determine the short-distance
coefficients appearing in the factorization formula. We also point out how one
may systematically include relativistic corrections in these calculations.Comment: 25 pages, 3 postscript figures, use Revtex and epsfig.sty We fixed
some typos, added some text regarding a reference, and changed some
equations. The file will be available at http://phenom.physics.wisc.edu
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