1,208 research outputs found
Direction Judgement Errors in Perspective Displays
Spatial information transfer characteristics of perspective situation displays were investigated by having eight subjects judge the directions of displayed targets relative to a fixed position in the center of computer generated perspective scenes. Their errors in judging azimuth angles varied sinusoidally with the azimuth of the targets. Errors alternated between clockwise and counterclock wise from one direction quadrant to the next. As the perspective geometry was varied between telephoto lens and wide angle lens views, the direction of error gradually reversed in all quadrants. The results can be explained by systematic differences between the three-dimensional stimulus angles and the perspective projections of those angles onto the display screen
The Large N Harmonic Oscillator as a String Theory
We propose a duality between the large-N gauged harmonic oscillator and a
novel string theory in two dimensions.Comment: 31 pages, 2 figures; v2: fixed typo
A quantum electron star
We construct and probe a holographic description of state of matter which
results from coupling a Fermi liquid to a relativistic conformal field theory
(CFT). The bulk solution is described by a quantum gas of fermions supported
from collapse into the gravitational well of AdS by their own electrostatic
repulsion. In the probe limit studied here, the Landau quasiparticles survive
this coupling to a CFT.Comment: 8 pages, 7 figure
Virtual space and 2-dimensional effects in perspective displays
When interpreting three dimensional spatial relationships presented on a two dimensional display surface, the viewer is required to mentally reconstruct the original information. This reconstruction is influenced by both the perspective geometry of the displayed image and the viewer's eye position relative to the display. In a study which manipulated these variables, subjects judged the azimuth direction of a target object relative to a reference object fixed in the center of a perspective display. The results support a previously developed model which predicted that the azimuth judgement error would be a sinusoidal function of stimulus azimuth. The amplitude of this function was correctly predicted to be systematically modulated by both the perspective geometry of the image and the viewer's eye position relative to the screen. Interaction of the two components of the model, the virtual space effect and the 3D-to-2D projection effect, predicted the relative amplitudes of the sinusoidal azimuth error functions for the various conditions of the experiment. Mean azimuth judgements in some directions differed by as much as 25 degrees as a result of different combinations of eye position and image geometry. The results illustrate the need to consider the effects of perspective geometry when designing spatial information instruments, and show the model to be a reliable predictor of average performance
Non-Abelian statistics versus the Witten anomaly
This paper is motivated by prospects for non-Abelian statistics of deconfined
particle-like objects in 3+1 dimensions, realized as solitons with localized
Majorana zeromodes. To this end, we study the fermionic collective coordinates
of magnetic monopoles in 3+1 dimensional spontaneously-broken SU(2) gauge
theories with various spectra of fermions. We argue that a single Majorana
zeromode of the monopole is not compatible with cancellation of the Witten
SU(2) anomaly. We also compare this approach with other attempts to realize
deconfined non-Abelian objects in 3+1 dimensions.Comment: 11 pages, 3 figures; v2: added refs, minor corrections, published
versio
Gravity duals for non-relativistic CFTs
We attempt to generalize the AdS/CFT correspondence to non-relativistic
conformal field theories which are invariant under Galilean transformations.
Such systems govern ultracold atoms at unitarity, nucleon scattering in some
channels, and more generally, a family of universality classes of quantum
critical behavior. We construct a family of metrics which realize these
symmetries as isometries. They are solutions of gravity with negative
cosmological constant coupled to pressureless dust. We discuss realizations of
the dust, which include a bulk superconductor. We develop the holographic
dictionary and compute some two-point correlators. A strange aspect of the
correspondence is that the bulk geometry has two extra noncompact dimensions.Comment: 12 pages; v2, v3, v4: added references, minor corrections; v3:
cleaned up and generalized dust; v4: closer to published versio
Correlated metallic state in honeycomb lattice: Orthogonal Dirac semimetal
A novel gapped metallic state coined orthogonal Dirac semimetal is proposed
in the honeycomb lattice in terms of slave-spin representation of
Hubbard model. This state corresponds to the disordered phase of slave-spin and
has the same thermaldynamical and transport properties as usual Dirac semimetal
but its singe-particle excitation is gapped and has nontrivial topological
order due to the gauge structure. The quantum phase transition from
this orthogonal Dirac semimetal to usual Dirac semimetal is described by a
mean-field decoupling with complementary fluctuation analysis and its
criticality falls into the universality class of 2+1D Ising model while a large
anomalous dimension for the physical electron is found at quantum critical
point (QCP), which could be considered as a fingerprint of our fractionalized
theory when compared to other non-fractionalized approaches. As byproducts, a
path integral formalism for the slave-spin representation of Hubbard
model is constructed and possible relations to other approaches and the
sublattice pairing states, which has been argued to be a promising candidate
for gapped spin liquid state found in the numerical simulation, are briefly
discussed. Additionally, when spin-orbit coupling is considered, the
instability of orthogonal Dirac semimetal to the fractionalized quantum spin
Hall insulator (fractionalized topological insulator) is also expected. We hope
the present work may be helpful for future studies in slave-spin theory
and related non-Fermi liquid phases in honeycomb lattice.Comment: 12 pages,no figures, more discussions added. arXiv admin note: text
overlap with arXiv:1203.063
Alternative Kondo breakdown mechanism: Orbital-selective orthogonal metal transition
In a recent paper of Nandkishore and Senthil [arxiv:1201.5998 (2012)], a
concept of orthogonal metal has been introduced to reinterpret the disordered
state of slave-spin representation in the Hubbard model as an exotic gapped
metallic state. We extend this concept to study the corresponding quantum phase
transition in the extended Anderson lattice model. It is found that the
disordered state of slave spins in this model is an orbital-selective
orthogonal metal, a generalization of the concept of the orthogonal metal in
the Hubbard model. Near the quantum critical point the essential behaviors are
dominated by a z = 3 critical mode, which is in contrast to the naive
expectation in the Hubbard model. The result provides alternative Kondo
breakdown mechanism for heavy fermion compounds underlying the physics of the
orbital-selective orthogonal metal in the disordered state, which is different
from the conventional Kondo breakdown mechanism with the fractionalized Fermi
liquid picture. This work is expected to be useful in understanding the quantum
criticality happening in some heavy fermion materials and other related
strongly correlated systems.Comment: 11 pages, no figures, significantly revised and reference added.
Comparison with conventional Kondo breakdown mechanism is discussed in a new
sectio
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