Extraterritorial Reach of the Great Writ at Common Law: The Constitution Guarantees the Guantanamo Bay Detainees a Right to Habeas Corpus

Tanulmányi rendszerbe betöltv

Academic Tenure and Academic Freedom

Anyone with enough interest in academic tenure to glance at this article knows what tenure is. Are you sure? Here are two rather varying definitions. The first, by a former president of Yale University, Kingman Brewster, is from the best brief statement about tenure in a research university: The practical fact in most places, and the unexceptional rule at Yale, is that tenure is for all normal purposes a guarantee of appointment until retirement age. The second, by Duke law professor William W. Van Alstyne, is found in the best general defense of tenure: Tenure, accurately and unequivocally defined, lays no claim whatever to a guarantee of lifetime employment. Rather, tenure provides only that no person continuously retained as a full-time faculty member beyond a specified lengthy period of probationary service may thereafter be dismissed without adequate cause. Both definitions are close to the truth: President Brewster\u27s as a realistic observation, Professor Van Alstyne\u27s as a cautious scholar\u27s synthesis. We will have more to say about their apparent differences. The conventions and legal status that both address affect all but a very few of the nation\u27s accredited universities and four-year colleges. This article will say little or nothing about two-year community colleges. While two-year institutions account for almost 40 percent of post-secondary enrollments, their practices range from a tenure system following the higher education model, to the public school model of granting tenure routinely after the teacher has served for two or three years without running into difficulties, to no tenure system at all

Quantum dots with two electrons: Singlet-triplet transitions

The magnetic character of the ground-state of two electrons on a double quantum dot, connected in series to left and right single-channel leads, is considered. By solving exactly for the spectrum of the two interacting electrons, it is found that the coupling to the continuum of propagating states on the leads, in conjunction with the electron-electron interactions, may result in a delocalization of the bound state of the two electrons. This, in turn, reduces significantly the range of the Coulomb interaction parameters over which singlet-triplet transitions can be realized. It is also found that the coupling to the leads favors the singlet ground-state.Comment: 8 pages, submitted to Phys. Rev.

Ground-state energy and spin in disordered quantum dots

We investigate the ground-state energy and spin of disordered quantum dots using spin-density-functional theory. Fluctuations of addition energies (Coulomb-blockade peak spacings) do not scale with average addition energy but remain proportional to level spacing. With increasing interaction strength, the even-odd alternation of addition energies disappears, and the probability of non-minimal spin increases, but never exceeds 50%. Within a two-orbital model, we show that the off-diagonal Coulomb matrix elements help stabilize a ground state of minimal spin.Comment: 10 pages, 2 figure

Scalar and vector Keldysh models in the time domain

The exactly solvable Keldysh model of disordered electron system in a random scattering field with extremely long correlation length is converted to the time-dependent model with extremely long relaxation. The dynamical problem is solved for the ensemble of two-level systems (TLS) with fluctuating well depths having the discrete Z_2 symmetry. It is shown also that the symmetric TLS with fluctuating barrier transparency may be described in terms of the planar Keldysh model with dime-dependent random planar rotations in xy plane having continuous SO(2) symmetry. The case of simultaneous fluctuations of the well depth and barrier transparency is subject to non-abelian algebra. Application of this model to description of dynamic fluctuations in quantum dots and optical lattices is discussed.Comment: 6 pages, 5 eps figures. Extended version of the paper to be published in JETP Lett 89 (2009

Nonequilibrium theory of Coulomb blockade in open quantum dots

We develop a non-equilibrium theory to describe weak Coulomb blockade effects in open quantum dots. Working within the bosonized description of electrons in the point contacts, we expose deficiencies in earlier applications of this method, and address them using a 1/N expansion in the inverse number of channels. At leading order this yields the self-consistent potential for the charging interaction. Coulomb blockade effects arise as quantum corrections to transport at the next order. Our approach unifies the phase functional and bosonization approaches to the problem, as well as providing a simple picture for the conductance corrections in terms of renormalization of the dot's elastic scattering matrix, which is obtained also by elementary perturbation theory. For the case of ideal contacts, a symmetry argument immediately allows us to conclude that interactions give no signature in the averaged conductance. Non-equilibrium applications to the pumped current in a quantum pump are worked out in detail.Comment: Published versio

Spin and Charge Correlations in Quantum Dots: An Exact Solution

The inclusion of charging and spin-exchange interactions within the Universal Hamiltonian description of quantum dots is challenging as it leads to a non-Abelian action. Here we present an {\it exact} analytical solution of the probem, in particular, in the vicinity of the Stoner instabilty point. We calculate several observables, including the tunneling density of states (TDOS) and the spin susceptibility. Near the instability point the TDOS exhibits a non-monotonous behavior as function of the tunneling energy, even at temperatures higher than the exchange energy. Our approach is generalizable to a broad set of observables, including the a.c. susceptibility and the absorption spectrum for anisotropic spin interaction. Our results could be tested in nearly ferromagnetic materials.Comment: JETPL class, 6 pages, 2 figure