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Consider the Hamiltonian system i = 1 , . . . , N. Here, H E C2(R2N, R). In this paper, we investigate the existence of periodic orbits of (HS) on a given energy surface X = { z E W Z N ; H ( z) = c} ( c > 0 is a constant). The surface I: is required to verify certain geometric assumptions: B bounds a star-shaped compact region B and u 8 c B c pS for some ellipsoid %‘c RZN, 0 < (Y < p. We exhib...

Is general equilibrium theory empirically testable? Our perspective on this question differs fromthe standard, Sonnenschein–Debreu–Mantel (SDM) viewpoint. While the SDM tradition considersaggregate (excess) demand as a function of prices, we suppose that what is observable is the equilibriumprice vector as a function of the fundamentals of the economy.We apply this perspective to anexchange eco...

This paper studies non-parametric identi…cation and the testable implications of the Roy Model. Results in the literature are generalized in three directions. First, my model allows fully general functions that characterize the income of di¤erent occupations. Second, identi…cation is obtained using strictly weaker exclusion restrictions. For example, the model with additive heterogeneity is non...

In the early days of superconductivity, Ivar Giaver discovered that it was possible to make a novel DC transformer by using one superconductor to drag vortices through another. An analogous effect was predicted to exist in quantum Hall bilayers and has recently been discovered experimentally by Eisenstein’s group at Caltech. Similarly, new experiments from the Caltech group have demonstrated th...

We establish several set-valued function versions of Ekeland’s variational principle and hence provide some sufficient conditions ensuring the existence of error bounds for inequality systems defined by finitely many lower semicontinuous functions.

We present a generalization of the Phelps lemma to locally convex topological vector spaces and show the equivalence of this theorem, Ekeland's principle and Dane s' drop theorem in locally convex spaces to their Banach space counterparts and to a Pareto eeciency theorem due to Isac. Concerning the drop theorem this solves a problem proposed by G. Isac in 1997. We show that another formulation ...

We propose a very weak type of generalized distance called weak τ -function and use it to weaken the assumptions about lower semicontinuity in existing formulations of Ekeland’s variational principle for a kind of minimizers of a set-valued mapping, which is different from the Pareto minimizer, and in recent results which are equivalent to Ekeland’s variational principle.

This paper addresses a large class of vector optimization problems in infinite-dimensional spaces with respect to two important binary relations derived from domination structures. Motivated by theoretical challenges as well applications some models behavioral sciences, we establish new variational principles that can be viewed far-going extensions the Ekeland principle cover settings. Our appr...