11,712 research outputs found
Herzberg Circuit and Berry's Phase in Chirality-based Coded Qubit in a Triangular Triple Quantum Dot
We present a theoretical proposal for the Herzberg circuit and controlled
accumulation of Berry's phase in a chirality-based coded qubit in a triangular
triple quantum dot molecule with one electron spin each. The qubit is encoded
in the two degenerate states of a three spin complex with total spin .
Using a Hubbard and Heisenberg model the Herzberg circuit encircling the
degeneracy point is realized by adiabatically tuning the successive on-site
energies of quantum dots and tunnel couplings across a pair of neighbouring
dots. It is explicitly shown that encircling the degeneracy point leads to the
accumulation of the geometrical Berrys phase. We show that only triangular but
not linear quantum dot molecule allows for the generation of Berry's phase and
we discuss a protocol to detect this geometrical phase
Integrated Light 2MASS IR Photometry of Galactic Globular Clusters
We have mosaiced 2MASS images to derive surface brightness profiles in JHK
for 104 Galactic globular clusters. We fit these with King profiles, and show
that the core radii are identical to within the errors for each of these IR
colors, and are identical to the core radii at V in essentially all cases. We
derive integrated light colors V-J, V-H, V-K_s, J-H and J-K_s for these
globular clusters. Each color shows a reasonably tight relation between the
dereddened colors and metallicity. Fits to these are given for each color. The
IR--IR colors have very small errors due largely to the all-sky photometric
calibration of the 2MASS survey, while the V-IR colors have substantially
larger uncertainties. We find fairly good agreement with measurements of
integrated light colors for a smaller sample of Galactic globular clusters by
Aaronson, Malkan & Kleinmann from 1977. Our results provide a calibration for
the integrated light of distant single burst old stellar populations from very
low to Solar metallicities. A comparison of our dereddened measured colors with
predictions from several models of the integrated light of single burst old
populations shows good agreement in the low metallicity domain for V-K_s
colors, but an offset at a fixed [Fe/H] of ~0.1 mag in J-K_s, which we ascribe
to photometric system transformation issues. Some of the models fail to
reproduce the behavior of the integrated light colors of the Galactic globular
clusters near Solar metallicity.Comment: Accepted for publication in the A
Differential contributions of A- and C-nociceptors to primary and secondary inflammatory hypersensitivity in the rat
Primary hyperalgesia is characterized by increased responsiveness to both heat and mechanical stimulation in the area of injury. By contrast, secondary hyperalgesia is generally associated with increased responses to mechanical but not heat stimuli. We tested the hypothesis that sensitization in secondary hyperalgesia is dependent on the class of peripheral nociceptor (C- or A-nociceptor) rather than the modality of stimulation (mechanical vs heat). A- and C-nociceptors were selectively activated using contact heat ramps applied to the hind paw dorsum in animals with hind paw inflammation (primary hyperalgesia) and knee inflammatory arthritis (secondary hyperalgesia). Sensitization to A- and C-nociceptor activation in primary and secondary hyperalgesia was assessed by reflex withdrawal thresholds and by Fos immunocytochemistry in the dorsal horn of the spinal cord, as an index of neuronal activation. In primary hyperalgesia, only C-nociceptor-evoked withdrawal reflexes were sensitized. This was associated with increased spinal lamina I neuronal activation to both A- and C-nociceptor activation. Fos-like immunoreactivity (FLI) was unchanged in other dorsal horn laminae. In secondary hyperalgesia, only A-nociceptor-evoked withdrawal reflexes were sensitized, and FLI was increased in both superficial and deep dorsal laminae. Neurons in the superficial dorsal horn receive and process nociceptor inputs from the area of primary hyperalgesia, resulting in functional sensitization to C-nociceptive inputs. In inflammatory arthritis, secondary hyperalgesia is evoked by A-nociceptor thermal stimulation, suggesting that secondary hyperalgesia is A-nociceptor, rather than stimulus modality (mechanical vs thermal), dependent. Fos-like immunoreactivity evoked by A-nociceptor stimulation in secondary hyperalgesia suggests that the sensitization is underpinned by spinal neuronal sensitization in laminae I and IV/V
Fermi surface topology and low-lying quasiparticle structure of magnetically ordered Fe1+xTe
We report the first photoemission study of Fe1+xTe - the host compound of the
newly discovered iron-chalcogenide superconductors. Our results reveal a pair
of nearly electron- hole compensated Fermi pockets, strong Fermi velocity
renormalization and an absence of a spin-density-wave gap. A shadow hole pocket
is observed at the "X"-point of the Brillouin zone which is consistent with a
long-range ordered magneto-structural groundstate. No signature of Fermi
surface nesting instability associated with Q= pi(1/2, 1/2) is observed. Our
results collectively reveal that the Fe1+xTe series is dramatically different
from the undoped phases of the high Tc pnictides and likely harbor unusual
mechanism for superconductivity and quantum magnetic order.Comment: 5 pages, 4 Figures; Submitted to Phys. Rev. Lett. (2009
Quantum properties of the Dirac field on BTZ black hole backgrounds
We consider a Dirac field on a -dimensional uncharged BTZ black hole
background. We first find out the Dirac Hamiltonian, and study its
self-adjointness properties. We find that, in analogy to the Kerr-Newman-AdS
Dirac Hamiltonian in dimensions, essential self-adjointness on
of the reduced (radial) Hamiltonian is implemented
only if a suitable relation between the mass of the Dirac field and the
cosmological radius holds true. The very presence of a boundary-like
behaviour of is at the root of this problem. Also, we determine in a
complete way qualitative spectral properties for the non-extremal case, for
which we can infer the absence of quantum bound states for the Dirac field.
Next, we investigate the possibility of a quantum loss of angular momentum for
the -dimensional uncharged BTZ black hole. Unlike the corresponding
stationary four-dimensional solutions, the formal treatment of the level
crossing mechanism is much simpler. We find that, even in the extremal case, no
level crossing takes place. Therefore, no quantum loss of angular momentum via
particle pair production is allowed.Comment: 19 pages; IOP styl
Volume Fractions of the Kinematic "Near-Critical" Sets of the Quantum Ensemble Control Landscape
An estimate is derived for the volume fraction of a subset in the neighborhood
of the critical set
of the kinematic quantum ensemble control landscape J(U) = Tr(U\rho U' O),
where represents the unitary time evolution operator, {\rho} is the initial
density matrix of the ensemble, and O is an observable operator. This estimate
is based on the Hilbert-Schmidt geometry for the unitary group and a
first-order approximation of . An upper bound on these
near-critical volumes is conjectured and supported by numerical simulation,
leading to an asymptotic analysis as the dimension of the quantum system
rises in which the volume fractions of these "near-critical" sets decrease to
zero as increases. This result helps explain the apparent lack of influence
exerted by the many saddles of over the gradient flow.Comment: 27 pages, 1 figur
A topological insulator surface under strong Coulomb, magnetic and disorder perturbations
Three dimensional topological insulators embody a newly discovered state of
matter characterized by conducting spin-momentum locked surface states that
span the bulk band gap as demonstrated via spin-resolved ARPES measurements .
This highly unusual surface environment provides a rich ground for the
discovery of novel physical phenomena. Here we present the first controlled
study of the topological insulator surfaces under strong Coulomb, magnetic and
disorder perturbations. We have used interaction of iron, with a large Coulomb
state and significant magnetic moment as a probe to \textit{systematically test
the robustness} of the topological surface states of the model topological
insulator BiSe. We observe that strong perturbation leads to the
creation of odd multiples of Dirac fermions and that magnetic interactions
break time reversal symmetry in the presence of band hybridization. We also
present a theoretical model to account for the altered surface of BiSe.
Taken collectively, these results are a critical guide in manipulating
topological surfaces for probing fundamental physics or developing device
applications.Comment: 14 pages, 4 Figures. arXiv admin note: substantial text overlap with
arXiv:1009.621
Unsteady flow in a supercritical supersonic diffuser
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77051/1/AIAA-10045-786.pd
- …