5,342 research outputs found
Semidirect product gauge group and quantization of hypercharge
In the Standard Model the hypercharges of quarks and leptons are not
determined by the gauge group alone. We show that, if we choose the semidirect product group
as its gauge group,
the hyperchages are settled to be . In
addition, the conditions for gauge-anomaly cancellation give strong
constraints. As a result, the ratios of the hypercharges are uniquely
determined and the gravitational anomaly is automatically canceled. The
standard charge assignment to quarks and leptons can be properly reproduced.
For exotic matter fields their hypercharges are also discussed.Comment: 17 pages, 2 tables; LaTeX; typos corrected, references added or
replaced, argument in Secs. 2 and 3 revised, results unchanged; to be
published in Phys. Rew.
SDW and FISDW transition of (TMTSF)ClO at high magnetic fields
The magnetic field dependence of the SDW transition in (TMTSF)ClO for
various anion cooling rates has been measured, with the field up to 27T
parallel to the lowest conductivity direction . For quenched
(TMTSF)ClO, the SDW transition temperature increases
from 4.5K in zero field up to 8.4K at 27T. A quadratic behavior is observed
below 18T, followed by a saturation behavior. These results are consistent with
the prediction of the mean-field theory. From these behaviors,
is estimated as =13.5K for the perfect nesting case. This
indicates that the SDW phase in quenched (TMTSF)ClO, where is less than 6K, is strongly suppressed by the two-dimensionality of
the system. In the intermediate cooled state in which the SDW phase does not
appear in zero field, the transition temperature for the field-induced SDW
shows a quadratic behavior above 12T and there is no saturation behavior even
at 27T, in contrast to the FISDW phase in the relaxed state. This behavior can
probably be attributed to the difference of the dimerized gap due to anion
ordering.Comment: 4pages,5figures(EPS), accepted for publication in PR
Role of the dimerized gap due to anion ordering in spin-density wave phase of (TMTSF)ClO at high magnetic fields
Magnetoresistance measurements have been carried out along the highly
conducting a axis in the FISDW phase of hydrogened and deuterated
(TMTSF)ClO for various cooling rates through the anion ordering
temperature. With increasing the cooling rate, a) the high field phase boundary
, observed at 27 T in hydrogened samples for slowly cooled,
is shifted towards a lower field, b) the last semimetallic SDW phase below
is suppressed, and c) the FISDW insulating phase above
is enhanced in both salts. The cooling rate dependence of
the FISDW transition and of in both salts can be explained
by taking into account the peculiar SDW nesting vector stabilized by the
dimerized gap due to anion ordering.Comment: 6pages,6figures(EPS), accepted for publication in PR
Lossy data compression with random gates
We introduce a new protocol for a lossy data compression algorithm which is
based on constraint satisfaction gates. We show that the theoretical capacity
of algorithms built from standard parity-check gates converges exponentially
fast to the Shannon's bound when the number of variables seen by each gate
increases. We then generalize this approach by introducing random gates. They
have theoretical performances nearly as good as parity checks, but they offer
the great advantage that the encoding can be done in linear time using the
Survey Inspired Decimation algorithm, a powerful algorithm for constraint
satisfaction problems derived from statistical physics
Magnetic irreversibility and Verwey transition in nano-crystalline bacterial magnetite
The magnetic properties of biologically-produced magnetite nanocrystals
biomineralized by four different magnetotactic bacteria were compared to those
of synthetic magnetite nanocrystals and large, high quality single crystals.
The magnetic feature at the Verwey temperature, , was clearly seen in
all nanocrystals, although its sharpness depended on the shape of individual
nanoparticles and whether or not the particles were arranged in magnetosome
chains. The transition was broader in the individual superparamagnetic
nanoparticles for which , where is the superparamagnetic
blocking temperature. For the nanocrystals organized in chains, the effective
blocking temperature and the Verwey transition is sharply
defined. No correlation between the particle size and was found.
Furthermore, measurements of suggest that magnetosome chains
behave as long magnetic dipoles where the local magnetic field is directed
along the chain and this result confirms that time-logarithmic magnetic
relaxation is due to the collective (dipolar) nature of the barrier for
magnetic moment reorientation
The Distance to the Galactic Center Derived From Infrared Photometry of Bulge Red Clump Stars
On the basis of the near infrared observations of bulge red clump stars near
the Galactic center, we have determined the galactocentric distance to be R_0 =
7.52 +- 0.10 (stat) +- 0.35 (sys) kpc. We observed the red clump stars at |l| <
1.0 deg and 0.7 deg < |b| < 1.0 deg with the IRSF 1.4 m telescope and the
SIRIUS camera in the H and Ks bands. After extinction and population
corrections, we obtained (m - M)_0 = 14.38 +- 0.03 (stat) +- 0.10 (sys). The
statistical error is dominated by the uncertainty of the intrinsic local red
clump stars' luminosity. The systematic error is estimated to be +- 0.10
including uncertainties in extinction and population correction, zero-point of
photometry, and the fitting of the luminosity function of the red clump stars.
Our result, R_0 = 7.52 kpc, is in excellent agreement with the distance
determined geometrically with the star orbiting the massive black hole in the
Galactic center. The recent result based on the spatial distribution of
globular clusters is also consistent with our result. In addition, our study
exhibits that the distance determination to the Galactic center with the red
clump stars, even if the error of the population correction is taken into
account, can achieve an uncertainty of about 5%, which is almost the same level
as that in recent geometrical determinations.Comment: 14 pages, 4 figures, accepted by Ap
The Classification of Obsessive–Compulsive and Related Disorders in the ICD-11
Background To present the rationale for the new Obsessive–Compulsive and Related Disorders (OCRD) grouping in the Mental and Behavioural Disorders chapter of the Eleventh Revision of the World Health Organization’s International Classification of Diseases and Related Health Problems (ICD-11), including the conceptualization and essential features of disorders in this grouping. Methods Review of the recommendations of the ICD-11 Working Group on the Classification for OCRD. These sought to maximize clinical utility, global applicability, and scientific validity. Results The rationale for the grouping is based on common clinical features of included disorders including repetitive unwanted thoughts and associated behaviours, and is supported by emerging evidence from imaging, neurochemical, and genetic studies. The proposed grouping includes obsessive–compulsive disorder, body dysmorphic disorder, hypochondriasis, olfactory reference disorder, and hoarding disorder. Body-focused repetitive behaviour disorders, including trichotillomania and excoriation disorder are also included. Tourette disorder, a neurological disorder in ICD-11, and personality disorder with anankastic features, a personality disorder in ICD-11, are recommended for cross-referencing. Limitations Alternative nosological conceptualizations have been described in the literature and have some merit and empirical basis. Further work is needed to determine whether the proposed ICD-11 OCRD grouping and diagnostic guidelines are mostly likely to achieve the goals of maximizing clinical utility and global applicability. Conclusion It is anticipated that creation of an OCRD grouping will contribute to accurate identification and appropriate treatment of affected patients as well as research efforts aimed at improving our understanding of the prevalence, assessment, and management of its constituent disorders
- …