3,930 research outputs found
On F-theory E_6 GUTs
We approach the Minimum Supersymmetric Standard Model (MSSM) from an E_6 GUT
by using the spectral cover construction and non-abelian gauge fluxes in
F-theory. We start with an E_6 singularity unfolded from an E_8 singularity and
obtain E_6 GUTs by using an SU(3) spectral cover. By turning on SU(2) X U(1)^2
gauge fluxes, we obtain a rank 5 model with the gauge group SU(3) X SU(2) X
U(1)^2. Based on the well-studied geometric backgrounds in the literature, we
demonstrate several models and discuss their phenomenology.Comment: 42 pages, 17 tables; typos corrected, clarifications added, and
references adde
Rashba Spin Interferometer
A spin interferometer utilizing the Rashba effect is proposed. The novel
design is composed of a one-dimensional (1D) straight wire and a 1D half-ring.
By calculating the norm of the superposed wave function, we derive analytical
expressions to describe the spin interference spectrum as a function of the
Rashba coupling strength. Presented spin interference results are identified to
include (i) the quantum-mechanical 4pi rotation effect, (ii) geometric effect,
and (iii) Shubnikov-de Haas-like beating effect.Comment: 3 pages, 3 figures, appears in the proceedings of the 10th Joint
MMM/Intermag Conferenc
Quantum World-line Monte Carlo Method with Non-binary Loops and Its Application
A quantum world-line Monte Carlo method for high-symmetrical quantum models
is proposed. Firstly, based on a representation of a partition function using
the Matsubara formula, the principle of quantum world-line Monte Carlo methods
is briefly outlined and a new algorithm using non-binary loops is given for
quantum models with high symmetry as SU(N). The algorithm is called non-binary
loop algorithm because of non-binary loop updatings. Secondary, one example of
our numerical studies using the non-binary loop updating is shown. It is the
problem of the ground state of two-dimensional SU(N) anti-ferromagnets. Our
numerical study confirms that the ground state in the small N <= 4 case is a
magnetic ordered Neel state, but the one in the large N >= 5 case has no
magnetic order, and it becomes a dimer state.Comment: 14 pages, 5 figures, Invited talk at the 18th Annual Workshop on
Recent Developments of Computer Simulation Studies in Condensed Matter
Physics, Athens, 7-11 March, 200
Realistic Type IIB Supersymmetric Minkowski Flux Vacua
We show that there exist supersymmetric Minkowski vacua on Type IIB toroidal
orientifold with general flux compactifications where the RR tadpole
cancellation conditions can be relaxed elegantly. Then we present a realistic
Pati-Salam like model. At the string scale, the gauge symmetry can be broken
down to the Standard Model (SM) gauge symmetry, the gauge coupling unification
can be achieved naturally, and all the extra chiral exotic particles can be
decoupled so that we have the supersymmetric SMs with/without SM singlet(s)
below the string scale. The observed SM fermion masses and mixings can also be
obtained. In addition, the unified gauge coupling, the dilaton, the complex
structure moduli, the real parts of the K\"ahler moduli and the sum of the
imaginary parts of the K\"ahler moduli can be determined as functions of the
four-dimensional dilaton and fluxes, and can be estimated as well.Comment: RevTex4, 4 pages, 3 table
Broken spin-Hall accumulation symmetry by magnetic field and coexisted Rashba and Dresselhaus interactions
The spin-Hall effect in the two-dimensional electron gas (2DEG) generates
symmetric out-of-plane spin Sz accumulation about the current axis in the
absence of external magnetic field. Here we employ the real space
Landauer-Keldysh formalism [B. K. Nikolic et al., Phys. Rev. Lett. 95, 046601
(2005); Phys. Rev. B 73, 075303 (2006)] by considering a four-terminal setup to
investigate the circumstances in which this symmetry is broken. For the absence
of Dresselhaus interaction, starting from the applied out-of-plane B
corresponding to Zeeman splitting energy 0 - 0.5 times the Rashba hopping
energy tR, the breaking process is clearly seen. The influence of the Rashba
interaction on the magnetization of the 2DEG is studied herein. For coexisted
Rashba tR and Dresselhaus tD spin-orbit couplings in the absence of B,
interchanging tR and tD reverses the entire accumulation pattern.Comment: 3 pages, 2 figures, appears in the proceedings of 10th MMM/INTERMAG
conferenc
A Synthetical Approach for Blog Recommendation Mechanism: Trust, Social Relation, and Semantic Analysis
Weblog is a good paradigm of online social network which constitutes web-based regularly updated journals with reverse chronological sequences of dated entries, usually with blogrolls on the sidebars, allowing bloggers link to favorite site which they are frequently visited. In this study we propose an elaborate blog recommendation mechanism that combines trust model, social relation and semantic analysis and illustrate how it can be applied to a prestigious online blogging system – Wretch in Taiwan. By preliminary results of experimental study, we found some implications and empirically prove some theories in domain of social networking, and the example reveals that the proposed recommendation mechanism is quite feasible and promising
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