1,643 research outputs found
Controlling for Lexical Closeness in Survey Research: A Demonstration on the Technology Acceptance Model
Word co-occurrences in text carry lexical information that can be harvested by data-mining tools such as latent semantic analysis (LSA). In this research perspective paper, we demonstrate the potency of using such embedded information by demonstrating that the technology acceptance model (TAM) can be reconstructed significantly by analyzing unrelated newspaper articles. We suggest that part of the reason for the phenomenal statistical validity of TAM across contexts may be related to the lexical closeness among the keywords in its measurement items. We do so not to critique TAM but to praise the quality of its methodology. Next, putting that LSA reconstruction of TAM into perspective, we show that empirical data can provide a significantly better fitting model than LSA data can. Combined, the results raise the possibility that a significant portion of variance in survey based research results from word cooccurrences in the language itself regardless of the theory or context of the study. Addressing this possibility, we suggest a method to statistically control for lexical closeness
Dimer coverings on the Sierpinski gasket with possible vacancies on the outmost vertices
We present the number of dimers on the Sierpinski gasket
at stage with dimension equal to two, three, four or five, where one of
the outmost vertices is not covered when the number of vertices is an
odd number. The entropy of absorption of diatomic molecules per site, defined
as , is calculated to be
exactly for . The numbers of dimers on the generalized
Sierpinski gasket with and are also obtained
exactly. Their entropies are equal to , , ,
respectively. The upper and lower bounds for the entropy are derived in terms
of the results at a certain stage for with . As the
difference between these bounds converges quickly to zero as the calculated
stage increases, the numerical value of with can be
evaluated with more than a hundred significant figures accurate.Comment: 35 pages, 20 figures and 1 tabl
Critical Behavior of the Ferromagnetic Ising Model on a Sierpinski Carpet: Monte Carlo Renormalization Group Study
We perform a Monte Carlo Renormalization Group analysis of the critical
behavior of the ferromagnetic Ising model on a Sierpi\'nski fractal with
Hausdorff dimension . This method is shown to be relevant to
the calculation of the critical temperature and the magnetic
eigen-exponent on such structures. On the other hand, scaling corrections
hinder the calculation of the temperature eigen-exponent . At last, the
results are shown to be consistent with a finite size scaling analysis.Comment: 16 pages, 7 figure
Transmission phase lapses in quantum dots: the role of dot-lead coupling asymmetry
Lapses of transmission phase in transport through quantum dots are ubiquitous
already in the absence of interaction, in which case their precise location is
determined by the signs and magnitudes of the tunnelling matrix elements.
However, actual measurements for a quantum dot embedded in an Aharonov-Bohm
interferometer show systematic sequences of phase lapses separated by Coulomb
peaks -- an issue that attracted much attention and generated controversy.
Using a two-level quantum dot as an example we show that this phenomenon can be
accounted for by the combined effect of asymmetric dot-lead couplings (left
lead/right lead asymmetry as well as different level broadening for different
levels) and interaction-induced "population switching" of the levels, rendering
this behaviour generic. We construct and analyse a mean field scheme for an
interacting quantum dot, and investigate the properties of the mean field
solution, paying special attention to the character of its dependence
(continuous vs. discontinuous) on the chemical potential or gate voltage.Comment: 34 LaTeX pages in IOP format, 9 figures; misprints correcte
Spontaneous magnetization of the Ising model on the Sierpinski carpet fractal, a rigorous result
We give a rigorous proof of the existence of spontaneous magnetization at
finite temperature for the Ising spin model defined on the Sierpinski carpet
fractal. The theorem is inspired by the classical Peierls argument for the two
dimensional lattice. Therefore, this exact result proves the existence of
spontaneous magnetization for the Ising model in low dimensional structures,
i.e. structures with dimension smaller than 2.Comment: 14 pages, 8 figure
Geometric nature of the environment-induced Berry phase and geometric dephasing
We investigate the geometric phase or Berry phase (BP) acquired by a
spin-half which is both subject to a slowly varying magnetic field and
weakly-coupled to a dissipative environment (either quantum or classical). We
study how this phase is modified by the environment and find that the
modification is of a geometric nature. While the original BP (for an isolated
system) is the flux of a monopole-field through the loop traversed by the
magnetic field, the environment-induced modification of the BP is the flux of a
quadrupole-like field. We find that the environment-induced phase is complex,
and its imaginary part is a geometric contribution to dephasing. Its sign
depends on the direction of the loop. Unlike the BP, this geometric dephasing
is gauge invariant for open paths of the magnetic field.Comment: new version : more discussion and less technicalities (4pages 2fig
Dephasing due to Which Path Detector
We study dephasing of electrons induced by a which path detector and thus
verify Bohr's complementarity principle for fermions. We utilize a double path
interferometer with two slits, with one slit being replaced by a coherent
quantum dot (QD). A short one dimensional channel, in the form of a quantum
point contact (QPC), in close proximity to the QD, serves as a which path
detector. We find that by varying the properties of the QPC detector we affect
the visibility of the interference, inducing thus dephasing. We develop a
simple model to explain the dephasing due to the nearby detector and find good
agreement with the experiment.Comment: 8 pages, 3 figure
Hanbury-Brown and Twiss interference of anyons
We present a study of an Hanbury Brown and Twiss (HBT) interferometer
realized with anyons. Such a device can directly probe entanglement and
fractional statistics of initially uncorrelated particles. We calculate HBT
cross-correlations of Abelian Laughlin anyons. The correlations we calculate
exhibit partial bunching similar to bosons, indicating a substantial
statistical transmuta- tion from the underlying electronic degrees of freedom.
We also find qualitative differences between the anyonic signal and the
corresponding bosonic or fermionic signals, indicating that anyons cannot be
simply thought as intermediate between bosons and fermions.Comment: Refs adde
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