1,381 research outputs found
Thermally-induced magnetic phases in an Ising spin Kondo lattice model on a kagome lattice at 1/3-filling
Numerical investigation on the thermodynamic properties of an Ising spin
Kondo lattice model on a kagome lattice is reported. By using Monte Carlo
simulation, we investigated the magnetic phases at 1/3-filling. We identified
two successive transitions from high-temperature paramagnetic state to a
Kosterlitz-Thouless-like phase in an intermediate temperature range and to a
partially disordered phase at a lower temperature. The partially disordered
state is characterized by coexistence of antiferromagnetic hexagons and
paramagnetic sites with period . We compare the results
with those for the triangular lattice case.Comment: 4 pages, 2 figure
Interplay of quantum and thermal fluctuations in a frustrated magnet
We demonstrate the presence of an extended critical phase in the transverse
field Ising magnet on the triangular lattice, in a regime where both thermal
and quantum fluctuations are important. We map out a complete phase diagram by
means of quantum Monte Carlo simulations, and find that the critical phase is
the result of thermal fluctuations destabilising an order established by the
quantum fluctuations. It is separated by two Kosterlitz-Thouless transitions
from the paramagnet on one hand and the quantum-fluctuation driven
three-sublattice ordered phase on the other. Our work provides further evidence
that the zero temperature quantum phase transition is in the 3d XY universality
class.Comment: 9 pages, revtex
Blowing up generalized Kahler 4-manifolds
We show that the blow-up of a generalized Kahler 4-manifold in a
nondegenerate complex point admits a generalized Kahler metric. As with the
blow-up of complex surfaces, this metric may be chosen to coincide with the
original outside a tubular neighbourhood of the exceptional divisor. To
accomplish this, we develop a blow-up operation for bi-Hermitian manifolds.Comment: 16 page
Bounded derived categories of very simple manifolds
An unrepresentable cohomological functor of finite type of the bounded
derived category of coherent sheaves of a compact complex manifold of dimension
greater than one with no proper closed subvariety is given explicitly in
categorical terms. This is a partial generalization of an impressive result due
to Bondal and Van den Bergh.Comment: 11 pages one important references is added, proof of lemma 2.1 (2)
and many typos are correcte
The photometric properties of a vast stellar substructure in the outskirts of M33
We have surveyed sq.degrees surrounding M33 with CFHT MegaCam in the
g and i filters, as part of the Pan-Andromeda Archaeological Survey. Our
observations are deep enough to resolve the top 4mags of the red giant branch
population in this galaxy. We have previously shown that the disk of M33 is
surrounded by a large, irregular, low-surface brightness substructure. Here, we
quantify the stellar populations and structure of this feature using the PAndAS
data. We show that the stellar populations of this feature are consistent with
an old population with dex and an interquartile range in
metallicity of dex. We construct a surface brightness map of M33 that
traces this feature to mags\,arcsec. At these low surface
brightness levels, the structure extends to projected radii of kpc from
the center of M33 in both the north-west and south-east quadrants of the
galaxy. Overall, the structure has an "S-shaped" appearance that broadly aligns
with the orientation of the HI disk warp. We calculate a lower limit to the
integrated luminosity of the structure of mags, comparable to a
bright dwarf galaxy such as Fornax or AndII and slightly less than $1\$ of the
total luminosity of M33. Further, we show that there is tentative evidence for
a distortion in the distribution of young stars near the edge of the HI disk
that occurs at similar azimuth to the warp in HI. The data also hint at a
low-level, extended stellar component at larger radius that may be a M33 halo
component. We revisit studies of M33 and its stellar populations in light of
these new results, and we discuss possible formation scenarios for the vast
stellar structure. Our favored model is that of the tidal disruption of M33 in
its orbit around M31.Comment: Accepted for publication in ApJ. 17 figures. ApJ preprint forma
Binaural interaction and the octave illusion
The auditory octave illusion arises when dichotically presented tones, one octave apart, alternate rapidly between the ears. Most subjects perceive an illusory sequence of monaural tones: A high tone in the right ear (RE) alternates with a low tone, incorrectly localized to the left ear (LE). Behavioral studies suggest that the perceived pitch follows the RE input, and the perceived location the higher-frequency sound. To explore the link between the perceived pitches and brain-level interactions of dichotic tones, magnetoencephalographic responses were recorded to 4 binaural combinations of 2-min long continuous 400- and 800-Hz tones and to 4 monaural tones. Responses to LE and RE inputs were distinguished by frequency-tagging the ear-specific stimuli at different modulation frequencies. During dichotic presentation, ipsilateral LE tones elicited weaker and ipsilateral RE tones stronger responses than when both ears received the same tone. During the most paradoxical stimulus—high tone to LE and low tone to RE perceived as a low tone in LE during the illusion—also the contralateral responses to LE tones were diminished. The results demonstrate modified binaural interaction of dichotic tones one octave apart, suggesting that this interaction contributes to pitch perception during the octave illusion.Peer reviewe
Willmore Surfaces of Constant Moebius Curvature
We study Willmore surfaces of constant Moebius curvature in . It is
proved that such a surface in must be part of a minimal surface in
or the Clifford torus. Another result in this paper is that an isotropic
surface (hence also Willmore) in of constant could only be part of a
complex curve in or the Veronese 2-sphere in . It is
conjectured that they are the only examples possible. The main ingredients of
the proofs are over-determined systems and isoparametric functions.Comment: 16 pages. Mistakes occured in the proof to the main theorem (Thm 3.6)
has been correcte
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