17,383 research outputs found
Low energy effective theory of Fermi surface coupled with U(1) gauge field in 2+1 dimensions
We study the low energy effective theory for a non-Fermi liquid state in 2+1
dimensions, where a transverse U(1) gauge field is coupled with a patch of
Fermi surface with N flavors of fermion in the large N limit. In the low energy
limit, quantum corrections are classified according to the genus of the 2d
surface on which Feynman diagrams can be drawn without a crossing in a double
line representation, and all planar diagrams are important in the leading
order. The emerging theory has the similar structure to the four dimensional
SU(N) gauge theory in the large N limit. Because of strong quantum fluctuations
caused by the abundant low energy excitations near the Fermi surface, low
energy fermions remain strongly coupled even in the large N limit. As a result,
there are infinitely many quantum corrections that contribute to the leading
frequency dependence of the Green's function of fermion on the Fermi surface.
On the contrary, the boson self energy is not modified beyond the one-loop
level and the theory is stable in the large N limit. The non-perturbative
nature of the theory also shows up in correlation functions of gauge invariant
operators.Comment: 14 pages, 20 figures; v2) Sec. V on correlation function of gauge
invariant operators added; v3) typos corrected, minor changes (to appear in
PRB
A Non-Fermi Liquid from a Charged Black Hole; A Critical Fermi Ball
Using the AdS/CFT correspondence, we calculate a fermionic spectral function
in a 2+1 dimensional non-relativistic quantum field theory which is dual to a
gravitational theory in the background with a charged black hole. The
spectral function shows no quasiparticle peak but the Fermi surface is still
well defined. Interestingly, all momentum points inside the Fermi surface are
critical and the gapless modes are defined in a {\it critical Fermi ball} in
the momentum space.Comment: v3) discussion on the singular nature of the zero energy peak added;
to appear in Phys. Rev.
Maximizing total job value on a single machine with job selection
This paper describes a single machine scheduling problem of maximizing total job value with a machine availability constraint. The value of each job decreases over time in a stepwise fashion. Several solution properties of the problem are developed. Based on the properties, a branch-and-bound algorithm and a heuristic algorithm are derived. These algorithms are evaluated in the computational study and the results show that the heuristic algorithm provides effective solutions within short computation times
Concurrent Magnetic and Metal-Insulator Transitions in (Eu,Sm)B_6 Single Crystals
The effects of magnetic doping on a EuB_6 single crystal were investigated
based on magnetic and transport measurements. A modest 5% Sm substitution for
Eu changes the magnetic and transport properties dramatically and gives rise to
concurrent antiferromagnetic and metal-insulator transitions (MIT) from
ferromagnetic MIT for EuB6. Magnetic doping simultaneously changes the
itinerant carrier density and the magnetic interactions. We discuss the origin
of the concurrent magnetic MIT in (Eu,Sm)B_6.Comment: 13 pages, 3 figures, final version to appear in Appl. Phys. Lett
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