493 research outputs found
Efficient Basis Formulation for (1+1)-Dimensional SU(2) Lattice Gauge Theory: Spectral calculations with matrix product states
We propose an explicit formulation of the physical subspace for a
(1+1)-dimensional SU(2) lattice gauge theory, where the gauge degrees of
freedom are integrated out. Our formulation is completely general, and might be
potentially suited for the design of future quantum simulators. Additionally,
it allows for addressing the theory numerically with matrix product states. We
apply this technique to explore the spectral properties of the model and the
effect of truncating the gauge degrees of freedom to a small finite dimension.
In particular, we determine the scaling exponents for the vector mass.
Furthermore, we also compute the entanglement entropy in the ground state and
study its scaling towards the continuum limit.Comment: 19 pages, 16 figures, version 2: published versio
Thermal evolution of the Schwinger model with Matrix Product Operators
We demonstrate the suitability of tensor network techniques for describing
the thermal evolution of lattice gauge theories. As a benchmark case, we have
studied the temperature dependence of the chiral condensate in the Schwinger
model, using matrix product operators to approximate the thermal equilibrium
states for finite system sizes with non-zero lattice spacings. We show how
these techniques allow for reliable extrapolations in bond dimension, step
width, system size and lattice spacing, and for a systematic estimation and
control of all error sources involved in the calculation. The reached values of
the lattice spacing are small enough to capture the most challenging region of
high temperatures and the final results are consistent with the analytical
prediction by Sachs and Wipf over a broad temperature range.Comment: 6 pages, 11 figure
Density Induced Phase Transitions in the Schwinger Model: A Study with Matrix Product States
We numerically study the zero temperature phase structure of the multiflavor
Schwinger model at nonzero chemical potential. Using matrix product states, we
reproduce analytical results for the phase structure for two flavors in the
massless case and extend the computation to the massive case, where no
analytical predictions are available. Our calculations allow us to locate phase
transitions in the mass-chemical potential plane with great precision and
provide a concrete example of tensor networks overcoming the sign problem in a
lattice gauge theory calculation.Comment: 5+5 pages, 4+4 figures, version 2: different title, published versio
Venus and Leadership: Women Hospitality Leaders
The authors report on a survey of 234 women executives in the hospitality industry using factor analysis to discover the seven underlying dimensions of women leaders: perseverance, trust, inner values, responsibility, stewardship, communication, and vision
The spatiotemporal neural dynamics of object recognition for natural images and line drawings
Drawings offer a simple and efficient way to communicate meaning. While line drawings capture only coarsely how objects look in reality, we still perceive them as resembling real-world objects. Previous work has shown that this perceived similarity is mirrored by shared neural representations for drawings and natural images, which suggests that similar mechanisms underlie the recognition of both. However, other work has proposed that representations of drawings and natural images become similar only after substantial processing has taken place, suggesting distinct mechanisms. To arbitrate between those alternatives, we measured brain responses resolved in space and time using fMRI and MEG, respectively, while human participants (female and male) viewed images of objects depicted as photographs, line drawings, or sketch-like drawings. Using multivariate decoding, we demonstrate that object category information emerged similarly fast and across overlapping regions in occipital, ventral-temporal and posterior parietal cortex for all types of depiction, yet with smaller effects at higher levels of visual abstraction. In addition, cross-decoding between depiction types revealed strong generalization of object category information from early processing stages on. Finally, by combining fMRI and MEG data using representational similarity analysis, we found that visual information traversed similar processing stages for all types of depiction, yet with an overall stronger representation for photographs. Together our results demonstrate broad commonalities in the neural dynamics of object recognition across types of depiction, thus providing clear evidence for shared neural mechanisms underlying recognition of natural object images and abstract drawings
The spatiotemporal neural dynamics of object recognition for natural images and line drawings
Drawings offer a simple and efficient way to communicate meaning. While line drawings capture only coarsely how objects look in reality, we still perceive them as resembling real-world objects. Previous work has shown that this perceived similarity is mirrored by shared neural representations for drawings and natural images, which suggests that similar mechanisms underlie the recognition of both. However, other work has proposed that representations of drawings and natural images become similar only after substantial processing has taken place, suggesting distinct mechanisms. To arbitrate between those alternatives, we measured brain responses resolved in space and time using fMRI and MEG, respectively, while participants viewed images of objects depicted as photographs, line drawings, or sketch-like drawings. Using multivariate decoding, we demonstrate that object category information emerged similarly fast and across overlapping regions in occipital and ventral-temporal cortex for all types of depiction, yet with smaller effects at higher levels of visual abstraction. In addition, cross-decoding between depiction types revealed strong generalization of object category information from early processing stages on. Finally, by combining fMRI and MEG data using representational similarity analysis, we found that visual information traversed similar processing stages for all types of depiction, yet with an overall stronger representation for photographs. Together our results demonstrate broad commonalities in the neural dynamics of object recognition across types of depiction, thus providing clear evidence for shared neural mechanisms underlying recognition of natural object images and abstract drawings
The Five Essentials of Private Club Leadership
The authors examine underlying dimensions of private club leadership using principal components analysis. The data were collected between 1996 and 2003 from 702 club managers or club chief operating officers who are members of the Club Managers Association of America (CMAA). Five factors - innovation, vision, inner values, stewardship, and communication - were identified as essentials of private club leadership
Investigation of the 1+1 dimensional Thirring model using the method of matrix product states
We present preliminary results of a study on the non-thermal phase structure
of the (1+1) dimensional massive Thirring model, employing the method of matrix
product states. Through investigating the entanglement entropy, the fermion
correlators and the chiral condensate, it is found that this approach enables
us to observe numerical evidence of a Kosterlitz-Thouless phase transition in
the model.Comment: 7 pages, 4 figures; contribution to the proceedings of Lattice 2018
conferenc
The Spatiotemporal Neural Dynamics of Object Recognition for Natural Images and Line Drawings
Drawings offer a simple and efficient way to communicate meaning. While line drawings capture only coarsely how objects look in reality, we still perceive them as resembling real-world objects. Previous work has shown that this perceived similarity is mirrored by shared neural representations for drawings and natural images, which suggests that similar mechanisms underlie the recognition of both. However, other work has proposed that representations of drawings and natural images become similar only after substantial processing has taken place, suggesting distinct mechanisms. To arbitrate between those alternatives, we measured brain responses resolved in space and time using fMRI and MEG, respectively, while human participants (female and male) viewed images of objects depicted as photographs, line drawings, or sketch-like drawings. Using multivariate decoding, we demonstrate that object category information emerged similarly fast and across overlapping regions in occipital, ventral-temporal, and posterior parietal cortex for all types of depiction, yet with smaller effects at higher levels of visual abstraction. In addition, cross-decoding between depiction types revealed strong generalization of object category information from early processing stages on. Finally, by combining fMRI and MEG data using representational similarity analysis, we found that visual information traversed similar processing stages for all types of depiction, yet with an overall stronger representation for photographs. Together, our results demonstrate broad commonalities in the neural dynamics of object recognition across types of depiction, thus providing clear evidence for shared neural mechanisms underlying recognition of natural object images and abstract drawings
Magnetic Lifshitz transition and its consequences in multi-band iron-based superconductors
In this paper we address Lifshitz transition induced by applied external magnetic field in a case of iron-based superconductors, in which a difference between the Fermi level and the edges of the bands is relatively small. We introduce and investigate a two-band model with intra-band pairing in the relevant parameters regime to address a generic behaviour of a system with hole-like and electron-like bands in external magnetic field. Our results show that two Lifshitz transitions can develop in analysed systems and the first one occurs in the superconducting phase and takes place at approximately constant magnetic field. The chosen sets of the model parameters can describe characteristic band structure of iron-based superconductors and thus the obtained results can explain the experimental observations in FeSe and Co-doped BaFe2As2 compounds
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