15,313 research outputs found
Crystal and electronic structure of the room temperature organometallic ferrimagnet V(TCNE). Analysis of numerical DoS and magnetic properties as related to orbital and spin-Hamiltonian models
We present a detailed analysis of the results of our numerical study of the
crystal and electronic structure of the room temperature organometallic
ferrimagnet of general composition V(TCNE) with . The
results of the LSDA+ study show that the experimentally determined structure
complies with the magnetic measurements and thus can serve as a prototype
structure for the entire family of the M(TCNE) organometallic magnets.
The results of the numerical study and of the magnetic experiments are
interpreted using model Hamiltonians proposed here. This allowed us to obtain
estimates of the critical temperature in three- and two-dimensional regimes and
to give an explanation of the differences in behavior of probably isostructural
V(TCNE) and Fe(TCNE) species.Comment: 42 pages, 7 figure
Spin-Flavor Separation and Non-Fermi Liquid Behavior in the Multichannel Kondo Problem: A Large N Approach
We consider a generalization of the multichannel
single-impurity Kondo model which we solve analytically in the limit
, , with fixed. Non-Fermi
liquid behavior of the single electron Green function and of the local spin and
flavor susceptibilities occurs in both regimes, and , with
leading critical exponents {\em identical} to those found in the conformal
field theory solution for {\em all} and (with ). We explain
this remarkable agreement and connect it to ``spin-flavor separation", the
essential feature of the non-Fermi-liquid fixed point of the multichannel Kondo
problem.Comment: 14 pages, 1 Figure (Poscript file attached), Revte
A Case for Quantity Regulation
Contrary to the standard economic advice, many regulations of financial intermediaries, as well as other regulations such as blue laws, fishing rules, zoning restrictions, or pollution controls, take the form of quantity controls rather than taxes. We argue that costs of enforcement are crucial to understanding these choices. When violations of quantity regulations are cheaper to discover than failures to pay taxes, the former can emerge as the optimal instrument for the government, even when it is less attractive in the absence of enforcement costs. This analysis is especially relevant to situations where private enforcement of regulations is crucial.
A Case for Quantity Regulation
Contrary to the standard economic advice, many regulations of financial intermediaries, as well as other regulations such as blue laws, fishing rules, zoning restrictions, or pollution controls, take the form of quantity controls rather than taxes. We argue that costs of enforcement are crucial to understanding these choices. When violations of quantity regulations are cheaper to discover than failures to pay taxes, the former can emerge as the optimal instrument for the government, even when it is less attractive in the absence of enforcement costs. This analysis is especially relevant to situations where private enforcement of regulations is crucial.
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