Magnetization of Planar Four-Fermion Systems

We consider a planar system of fermions, at finite temperature and density, under a static magnetic field parallel to the two-dimensional plane. This magnetic field generates a Zeeman effect and, then, a spin polarization of the system. The critical properties are studied from the Landau's free energy. The possible observable consequences of the magnetization of planar systems such as polymer films and graphene are discussed.Comment: 10 pages, two-column, revtex style, 6 eps figures. Published versio

Rate equations for Coulomb blockade with ferromagnetic leads

We present a density-matrix rate-equation approach to sequential tunneling through a metal particle weakly coupled to ferromagnetic leads. The density-matrix description is able to deal with correlations between degenerate many-electron states that the standard rate equation formalism in terms of occupation probabilities cannot describe. Our formalism is valid for an arbitrary number of electrons on the dot, for an arbitrary angle between the polarization directions of the leads, and with or without spin-orbit scattering on the metal particle. Interestingly, we find that the density-matrix description may be necessary even for metal particles with unpolarized leads if three or more single-electron levels contribute to the transport current and electron-electron interactions in the metal particle are described by the `universal interaction Hamiltonian'.Comment: 10 pages, 4 figures, REVTeX

Constraints on Light Bottom Squarks from Radiative B-Meson Decays

The presence of a light b-squark (with mass about 4 GeV) and gluino (with mass about 15 GeV) might explain the observed excess in b-quark production at the Tevatron. Though provocative, this model is not excluded by present data. The light supersymmetric particles can induce large flavor-changing effects in radiative decays of B mesons. We analyse the decays B->X_s gamma and B->X_{sg} in this scenario and derive restrictive bounds on the flavor-changing quark-squark-gluino couplings.Comment: 14 pages, 3 figures. One reference added. Final version published in Physics Letters

Conductance Peak Height Correlations for a Coulomb-Blockaded Quantum Dot in a Weak Magnetic Field

We consider statistical correlations between the heights of conductance peaks corresponding to two different levels in a Coulomb-blockaded quantum dot. Correlations exist for two peaks at the same magnetic field if the field does not fully break time-reversal symmetry as well as for peaks at different values of a magnetic field that fully breaks time-reversal symmetry. Our results are also relevant to Coulomb-blockade conductance peak height statistics in the presence of weak spin-orbit coupling in a chaotic quantum dot.Comment: 5 pages, 3 figures, REVTeX 4, accepted for publication in Phys. Rev.

Conserved genes and pathways in primary human fibroblast strains undergoing replicative and radiation induced senescence

Additional file 3: Figure S3. Regulation of genes of Arrhythmogenic right ventricular cardiomyopathy pathway during senescence induction in HFF strains Genes of the “Arrhythmogenic right ventricular cardiomyopathy” pathway which are significantly up- (green) and down- (red) regulated (log2 fold change >1) during irradiation induced senescence (120 h after 20 Gy irradiation) in HFF strains. Orange color signifies genes which are commonly up-regulated during both, irradiation induced and replicative senescence

Electron Transport Through Nanoscopic Structures

This doctoral dissertation is concerned with modeling electron transport through nanoscopic structures, such as quantum dots, metal particles, or molecules. In Chapter 2, we consider statistical correlations between the heights of conductance peaks corresponding to two different levels in a Coulomb-blockaded quantum dot. Correlations exist for two peaks at the same magnetic field if the field does not fully break time-reversal symmetry as well as for peaks at different values of a magnetic field that fully breaks time-reversal symmetry. In Chapter 3, we present a density-matrix rate-equation approach to sequential tunneling through a metal particle weakly coupled to ferromagnetic leads. Our formalism is valid for an arbitrary number of electrons on the dot, for an arbitrary angle between the polarization directions of the leads, and with or without spin-orbit scattering on the metal particle. Interestingly, we find that the density-matrix description may be necessary even for metal particles with unpolarized leads if three or more single-electron levels contribute to the transport current and electron-electron interactions in the metal particle are described by the `universal interaction Hamiltonian'. In Chapters 4 and 5, we consider transport through molecular devices with strong coupling to a single vibrational mode for the case that the vibration is damped by coupling to the environment. We focus on the weak tunneling limit, for which a rate-equation approach is valid. The role of the environment can be characterized by a frequency-dependent frictional damping term and corresponding resonance frequency shift. We calculate current-voltage curves in Chapter 4 and find qualitative agreement between our theory and recent experiments on C_{60} single-molecule devices. In Chapter 5, we see that, depending on how the characteristic length scales of the van der Waals and electrostatic interaction of the molecule with the environment compare to each other, orthogonality catastrophe may appear or disappear, resulting in a smooth or discontinuous current-voltage curve, respectively. Finally, in Chapter 6, we investigate the influence of electron-phonon coupling on the current through a metallic single-walled carbon nanotube. In particular, we consider the high-energy optical and zone-boundary phonons and calculate an effective high-bias electron scattering rate, which is close to the experimentally observed value.Support by the Cornell Center for Materials Research (CCMR) under NSF grant no. DMR 0079992

Radiative B-Meson Decays

The presence of a light ˜ b squark (m ˜ b ∼ 4 GeV) and gluino (m˜g ∼ 15 GeV) might explain the observed excess in b-quark production at the Tevatron. Though provocative, this model is not excluded by present data. The light supersymmetric particles can induce large flavor-changing effects in radiative decays of B mesons. We analyse the decays B → Xsγ and B → Xsg in this scenario and derive restrictive bounds on the flavor-changing quark-squark-gluino couplings.