Non-integrability of Self-dual Yang-Mills-Higgs System

We examine integrability of self-dual Yang-Mills system in the Higgs phase, with taking simpler cases of vortices and domain walls. We show that the vortex equations and the domain-wall equations do not have Painleve property. This fact suggests that these equations are not integrable.Comment: 15 pages, no figures, v2: references added, v3: typos corrected, the final version to appear in NP

Solitons in Supersymmety Breaking Meta-Stable Vacua

In recently found supersymmetry-breaking meta-stable vacua of the supersymmetric QCD, we examine possible exsitence of solitons. Homotopy groups of the moduli space of the meta-stable vacua show that there is no nontrivial soliton for SU(N_c) gauge group. When U(1)_B symmetry present in the theory is gauged, we find non-BPS solitonic (vortex) strings whose existence and properties are predicted from brane configurations. We obtain explicit classical solutions which reproduce the predicitions. For SO(N_c) gauge group, we find there are solitonic strings for N = N_f-N_c+4 = 2, and Z_2 strings for the other N. The strings are meta-stable as they live in the meta-stable vacua.Comment: 30 pages, 14 figures, Comments on stability of non-BPS vortices are added, Comments on sigma model solitons are added, An appendix is adde

QCD String as Vortex String in Seiberg-Dual Theory

We construct a classical vortex string solution in a Seiberg-dual theory of N=1 supersymmetric SO(N_c) QCD which flows to a confining phase. We claim that this vortex string is a QCD string, as previouly argued by M.Strassler. In SO(N_c) QCD, it is known that stable QCD strings exist even in the presence of dynamical quarks. We show that our vortex strings are stable in the Seiberg-dual theory.Comment: 15 pages, 1 figur

1/2, 1/4 and 1/8 BPS Equations in SUSY Yang-Mills-Higgs Systems -- Field Theoretical Brane Configurations --

We systematically classify 1/2, 1/4 and 1/8 BPS equations in SUSY gauge theories in d=6, 5, 4, 3 and 2 with eight supercharges, with gauge groups and matter contents being arbitrary. Instantons (strings) and vortices (3-branes) are only allowed 1/2 BPS solitons in d=6 with N=1 SUSY. We find two 1/4 BPS equations and the unique 1/8 BPS equation in d=6 by considering configurations made of these field theory branes. All known BPS equations are rederived while several new 1/4 and 1/8 BPS equations are found in dimension less than six by dimensional reductions.Comment: 41 pages, no figures, v2: 49 pages, no figures, typos corrected, references added, the final version in NP

Scaling analysis of Kondo screening cloud in a mesoscopic ring with an embedded quantum dot

The Kondo effect is theoretically studied in a quantum dot embedded in a mesoscopic ring. The ring is connected to two external leads, which enables the transport measurement. Using the "poor man's" scaling method, we obtain analytical expressions of the Kondo temperature T_K as a function of the Aharonov-Bohm phase \phi by the magnetic flux penetrating the ring. In this Kondo problem, there are two characteristic lengths. One is the screening length of the charge fluctuation, L_c=\hbar v_F/ |\epsilon_0|, where v_F is the Fermi velocity and \epsilon_0 is the energy level in the quantum dot. The other is the screening length of spin fluctuation, i.e., size of Kondo screening cloud, L_K=\hbar v_F/ T_K. We obtain different expressions of T_K(\phi) for (i) L_c \ll L_K \ll L, (ii) L_c \ll L \ll L_K, and (iii) L \ll L_c \ll L_K, where L is the size of the ring. T_K is markedly modulated by \phi in cases (ii) and (iii), whereas it hardly depends on \phi in case (i). We also derive logarithmic corrections to the conductance at temperature T\gg T_K and an analytical expression of the conductance at T\ll T_K, on the basis of the scaling analysis.Comment: 21pages, 10 figure

Kondo Effect in Multiple-Dot Systems

We study the Kondo effect in multiple-dot systems for which the inter- as well as intra-dot Coulomb repulsions are strong, and the inter-dot tunneling is small. The application of the Ward-Takahashi identity to the inter-dot dynamical susceptibility enables us to analytically calculate the conductance for a double-dot system by using the Bethe-ansatz exact solution of the SU(4) impurity Anderson model. It is clarified how the inter-dot Kondo effect enhances or suppresses the conductance under the control of the gate voltage and the magnetic field. We then extend our analysis to multiple-dot systems including more than two dots, and discuss their characteristic transport properties by taking a triple-dot system as an example.Comment: 8 pages, 9 figure

Multi-parameter scaling of the Kondo effect in quantum dots with an even number of electrons

We address a recent theoretical discrepancy concerning the Kondo effect in quantum dots with an even number of electrons where spin-singlet and -triplet states are nearly degenerate. We show that the discrepancy arises from the fact that the Kondo scaling involves many parameters, which makes the results depend on concrete microscopic models. We illustrate this by the scaling calculations of the Kondo temperature, $T_K$, as a function of the energy difference between the singlet and triplet states $\Delta$. $T_K(\Delta)$ decreases with increasing $\Delta$, showing a crossover from a power law with a universal exponent to that with a nonuniversal exponent. The crossover depends on the initial parameters of the model.Comment: 8 pages, 3 figure

Enhanced spin Hall effect by tuning antidot potential: Proposal for a spin filter

We propose an efficient spin filter including an antidot fabricated on semiconductor heterostructures with strong spin-orbit interaction. The antidot creates a tunable potential on two-dimensional electron gas in the heterostructures, which may be attractive as well as repulsive. Our idea is based on the enhancement of extrinsic spin Hall effect by resonant scattering when the attractive potential is properly tuned. Numerical studies for three- and four-terminal devices indicate that the efficiency of the spin filter can be more than 50% by tuning the potential to the resonant condition.Comment: 11 pages, 10 figure

Radius Stabilization in a Supersymmetric Warped Compactification

A supersymmetric (SUSY) model of radius stabilization is constructed for the S^1/Z_2 warped compactifications with a hypermultiplet in five dimensions. Requiring the continuity of scalar field across the boundaries, we obtain radius stabilization preserving SUSY, realizing the SUSY extension of the Goldberger-Wise mechanism. Even if we allow discontinuities of the Z_2 odd field across the boundary, we always obtain SUSY preservation but obtain the radius stabilization only when the discontinuity is fixed by other mechanism.Comment: 6 pages, revtex, Errors of the products of distributions are corrected and the results are reanalyzed, references added, final version to appear in PR