58,148 research outputs found
BRST invariance and de Rham-type cohomology of 't Hooft-Polyakov monopole
We exploit the 't Hooft-Polyakov monopole to define closed algebra of the
quantum field operators and the BRST charge . In the first-class
configuration of the Dirac quantization, by including the -exact
gauge fixing term and the Faddeev-Popov ghost term, we find the BRST invariant
Hamiltonian to investigate the de Rham-type cohomology group structure for the
monopole system. The Bogomol'nyi bound is also discussed in terms of the
first-class topological charge defined on the extended internal 2-sphere.Comment: 8 page
Straight-line Drawability of a Planar Graph Plus an Edge
We investigate straight-line drawings of topological graphs that consist of a
planar graph plus one edge, also called almost-planar graphs. We present a
characterization of such graphs that admit a straight-line drawing. The
characterization enables a linear-time testing algorithm to determine whether
an almost-planar graph admits a straight-line drawing, and a linear-time
drawing algorithm that constructs such a drawing, if it exists. We also show
that some almost-planar graphs require exponential area for a straight-line
drawing
The Contribution of Hot Electron Spin Polarization to the Magnetotransport in a Spin-Valve Transistor at Finite Temperatures
The effect of spin mixing due to thermal spin waves and temperature
dependence of hot electron spin polarization to the collector current in a
spin-valve transistor has been theoretically explored. We calculate the
collector current as well as the temperature dependence of magnetocurrent at
finite temperatures to investigate the relative importance of spin mixing and
hot electron spin polarization. In this study the inelastic scattering events
in ferromagnetic layers have been taken into account to explore our interests.
The theoretical calculations suggest that the temperature dependence of hot
electron spin polarization has substantial contribution to the magnetotransport
in the spin-valve transistor.Comment: 8 pages and 6 figure
BRST extension of the Faddeev model
The Faddeev model is a second class constrained system. Here we construct its
nilpotent BRST operator and derive the ensuing manifestly BRST invariant
Lagrangian. Our construction employs the structure of Stuckelberg fields in a
nontrivial fashion.Comment: 4 pages, new references adde
The least common multiple of a sequence of products of linear polynomials
Let be the product of several linear polynomials with integer
coefficients. In this paper, we obtain the estimate: as , where is a constant depending on
.Comment: To appear in Acta Mathematica Hungaric
Asymptotic behavior of the least common multiple of consecutive arithmetic progression terms
Let and be two integers with , and let and be
integers with and . In this paper, we prove that , where is a constant depending on and .Comment: 8 pages. To appear in Archiv der Mathemati
Coupling of Josephson current qubits using a connecting loop
We propose a coupling scheme for the three-Josephson junction qubits which
uses a connecting loop, but not mutual inductance. Present scheme offers the
advantages of a large and tunable level splitting in implementing the
controlled-NOT (CNOT) operation. We calculate the switching probabilities of
the coupled qubits in the CNOT operations and demonstrate that present CNOT
gate can meet the criteria for the fault-tolerant quantum computing. We obtain
the coupling strength as a function of the coupling energy of the Josephson
junction and the length of the connecting loop which varies with selecting two
qubits from the scalable design.Comment: 5 pages with updates, version to appear in Phys. Rev.
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