4,098 research outputs found
D-instanton and polyinstanton effects from type I' D0-brane loops
We study non-perturbative D(-1)-instanton corrections to quartic gauge and
curvature couplings in 8d type IIB orientifolds, in terms of a one-loop
computation of BPS D0-branes in T-dual type I' models. The complete
perturbative and non-perturbative results are determined by the BPS
multiplicities of perturbative open strings and D0-brane bound states in the 9d
type I' theory. Its modular properties admit a geometric interpretation by
lifting to Horava-Witten theory. We use the type I' viewpoint to motivate a
proper interpretation of 8d and 4d polyinstanton effects, consistent with
heterotic - type II orientifold duality.Comment: 37 pages, 2 figures, clarifications and references adde
Field Tuning the G-Factor in InAs Nanowire Double Quantum Dots
We study the effects of magnetic and electric fields on the g-factors of
spins confined in a two-electron InAs nanowire double quantum dot. Spin
sensitive measurements are performed by monitoring the leakage current in the
Pauli blockade regime. Rotations of single spins are driven using
electric-dipole spin resonance. The g-factors are extracted from the spin
resonance condition as a function of the magnetic field direction, allowing
determination of the full g-tensor. Electric and magnetic field tuning can be
used to maximize the g-factor difference and in some cases altogether quench
the EDSR response, allowing selective single spin control.Comment: Related papers at http://pettagroup.princeton.ed
Higgs diphoton rate enhancement from supersymmetric physics beyond the MSSM
We show that supersymmetric "new physics" beyond the MSSM can naturally
accommodate a Higgs mass near 126 GeV and enhance the signal rate in the Higgs
to diphoton channel, while the signal rates in all the other Higgs decay
channels coincide with Standard Model expectations, except possibly the Higgs
to Z-photon channel. The "new physics" that corrects the relevant Higgs
couplings can be captured by two supersymmetric effective operators. We provide
a simple example of an underlying model in which these operators are
simultaneously generated. The scale of "new physics" that generates these
operators can be around 5 TeV or larger, and outside the reach of the LHC.Comment: 24 pages, 4 figure
Radio frequency charge sensing in InAs nanowire double quantum dots
We demonstrate charge sensing of an InAs nanowire double quantum dot (DQD)
coupled to a radio frequency (rf) circuit. We measure the rf signal reflected
by the resonator using homodyne detection. Clear single dot and DQD behavior
are observed in the resonator response. rf-reflectometry allows measurements of
the DQD charge stability diagram in the few-electron regime even when the dc
current through the device is too small to be measured. For a signal-to-noise
ratio of one, we estimate a minimum charge detection time of 350 microseconds
at interdot charge transitions and 9 microseconds for charge transitions with
the leads.Comment: Related papers at http://pettagroup.princeton.ed
Two-color QCD with staggered fermions at finite temperature under the influence of a magnetic field
In this paper we investigate the influence of a constant external magnetic
field on the finite-temperature phase structure and the chiral properties of a
simplified lattice model for QCD. We assume an SU(2) gauge symmetry and employ
dynamical staggered fermions of identical mass without rooting, corresponding
to Nf=4 flavors of identical electric charge. For fixed mass (given in lattice
units) the critical temperature is seen to rise with the magnetic field
strength. For three fixed beta-values, selected such that we stay (i) within
the chirally broken phase, (ii) within the transition region or (iii) within
the chirally restored phase, we study the approach to the chiral limit for
various values of the magnetic field. Within the chirally broken (confinement)
phase the chiral condensate is found to increase monotonically with a growing
magnetic field strength. In the chiral limit the increase starts linear in
agreement with a chiral model studied by Shushpanov and Smilga. Within the
chirally restored (deconfinement) phase the chiral condensate tends to zero in
the chiral limit, irrespective of the strength of the magnetic field.Comment: 15 pages, 12 figures; version accepted by Physical Review
Literacy: A cultural influence on functional left-right differences in the inferior parietal cortex
The current understanding of hemispheric interaction is limited. Functional hemispheric specialization is likely to depend on both genetic and environmental factors. In the present study we investigated the importance of one factor, literacy, for the functional lateralization in the inferior parietal cortex in two independent samples of literate and illiterate subjects. The results show that the illiterate group are consistently more right-lateralized than their literate controls. In contrast, the two groups showed a similar degree of left-right differences in early speech-related regions of the superior temporal cortex. These results provide evidence suggesting that a cultural factor, literacy, influences the functional hemispheric balance in reading and verbal working memory-related regions. In a third sample, we investigated grey and white matter with voxel-based morphometry. The results showed differences between literacy groups in white matter intensities related to the mid-body region of the corpus callosum and the inferior parietal and parietotemporal regions (literate > illiterate). There were no corresponding differences in the grey matter. This suggests that the influence of literacy on brain structure related to reading and verbal working memory is affecting large-scale brain connectivity more than grey matter per se
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