4,298 research outputs found
Results from the CDMS II Experiment
I report recent results and the status of the Cryogenic Dark Matter Search
(CDMS II) experiment at the Soudan Underground Laboratory in Minnesota, USA. A
blind analysis of data taken by 30 detectors between October 2006 and July 2007
found zero events consistent with WIMPs elastically scattering in our Ge
detectors. This resulted in an upper limit on the spin-independent,
WIMP-nucleon cross section of 6.6 x 10^-44 cm^2 (4.6 x 10^-44 cm^2 when
combined with our previous results) at the 90% C.L. for a WIMP of mass 60
GeV/c^2. In March 2009 data taking with CDMS II stopped in order to install the
first of 5 SuperTowers of detectors for the SuperCDMS Soudan project. Analysis
of data taken between August 2007 and March 2009 is ongoing.Comment: 5 pages, 4 figures, to appear in the proceedings of the TAUP09
conference (Rome, July 1st-5th 2009
Dark Matter as the signal of Grand Unification
We argue that the existence of Dark Matter (DM) is a possible consequence of
GUT symmetry breaking. In GUTs like SO(10), discrete Z_2 matter parity
(-1)^{3(B-L)} survives despite of broken B-L, and group theory uniquely
determines that the only possible Z_2-odd matter multiplets belong to
representation 16. We construct the minimal non-SUSY SO(10) model containing
one scalar 16 for DM and study its predictions below M_{G}. We find that EWSB
occurs radiatively due to DM couplings to the SM Higgs boson. For thermal relic
DM the mass range M_{DM}\sim (0.1-1) TeV is predicted by model perturbativity
up to M_{G}. For M_{DM}\sim (1) TeV to explain the observed cosmic ray
anomalies with DM decays, there exists a lower bound on the spin-independent
direct detection cross section within the reach of planned experiments.Comment: DM direct detection cross section is corrected by adding s-quark
contribution which turned out to be the dominant one. The prediction is just
below the present CDMS and XENON10 bound. Extended version, RGE-s included,
new references adde
Linkage study of the low-density lipoprotein-receptor gene and cholesterol levels in an Afrikaner family : quantitative genetics and identification of a minor founder effect
CITATION: Brink, P. A. et al. 1990. Linkage study of the low-density lipoprotein-receptor gene and cholesterol levels in an Afrikaner family : quantitative genetics and identification of a minor founder effect. South African Medical Journal, 77:292-296.The original publication is available at http://www.samj.org.zaOverlap of clinical and biochemical characteristics between hypercholesterolaemia in members of the general population and familial hypercholesterolaemic (FH) individuals may lead to misdiagnosis. Quantitative analyisis of family data may circumvent this problem. A way of looking for an association between plasma cholesterol levels and restriction fragment length polymorphism markers (RFLP) on the low-density lipoprotein (LDL) receptor gene by using reference cholesterol distributions was explored. Linkage, with a logarithm of the odds (LOD) score of 6,8 at θ 0, was detected between cholesterol levels and the LDL receptor in an extended Afrikaner family. Two RFLP-haplotypes, one previously found in a majority of Afrikaner FH homozygotes, and a second, Stu I -, BstE II +, Pvu II +, Nco I +, were associated with high cholesterol levels in this pedigree.Publisher’s versio
Ab initio determination of excitation energies and magnetic couplings in correlated, quasi two-dimensional iridates
To determine the strength of essential electronic and magnetic interactions
in the iridates SrIrO and BaIrO - potential platforms for
high-temperature superconductivity - we use many-body techniques from
wavefunction-based electronic-structure theory. Multiplet physics, spin-orbit
interactions, and Ir-O hybridization are all treated on equal footing, fully
{\it ab initio}. Our calculations put the lowest d-d excitations of
SrIrO/BaIrO at 0.69/0.64 eV, substantially lower than in
isostructural cuprates. Charge-transfer excitations start at 3.0/1.9 eV and the
magnetic nearest-neighbor exchange coupling is 51/58 meV. Available
experimental results are fully consistent with these values, which strongly
constrains the parametrization of effective iridate Hamiltonians
Ab initio computation of d-d excitation energies in low-dimensional Ti and V oxychlorides
Using a quantum chemical cluster-in-solid computational scheme, we calculate
the local d-d excitation energies for two strongly correlated Mott insulators,
the oxychlorides TiOCl and VOCl. TiOCl harbors quasi-one-dimensional spin
chains made out of S = 1/2 Ti3+ ions while the electronic structure of VOCl
displays a more two-dimensional character. We find in both cases that the
lowest-energy d-d excitations are within the t2g subshell, starting at 0.34 eV
and indicating that orbital degeneracies are significantly lifted. In the
vanadium oxychloride, spin triplet to singlet excitations are calculated to be
1 eV higher in energy. For TiOCl, the computed d-level electronic structure and
the symmetries of the wavefunctions are in very good agreement with resonant
inelastic x-ray scattering results and optical absorption data. For VOCl,
future resonant inelastic x-ray scattering experiments will constitute a direct
test of the symmetry and energy of about a dozen of different d-d excitations
that we predict here
Approach to the extremal limit of the Schwarzschild-de Sitter black hole
The quasinormal-mode spectrum of the Schwarzschild-de Sitter black hole is
studied in the limit of near-equal black-hole and cosmological radii. It is
found that the mode_frequencies_ agree with the P"oschl-Teller approximation to
one more order than previously realized, even though the effective_potential_
does not. Whether the spectrum approaches the limiting one uniformly in the
mode index is seen to depend on the chosen units (to the order investigated). A
perturbation framework is set up, in which these issues can be studied to
higher order in future.Comment: REVTeX4, 4pp., no figures. N.B. "Alec" is my first, and "Maassen van
den Brink" my family name. v2: added numerical verificatio
Research Methods for Psychology
This is a textbook for a research methods class in the social sciences. This book is OER and creative commons
Hate Talk, Straight Thought, and Wisdom: a guide to critical thinking, argumentation and decision making
This is an OER, creative commons textbook for a course on critical thinking, logic, reasoning, and argumentation
Poisson-Lie T-duality and N=2 superconformal WZNW models on compact groups
The supersymmetric generalization of Pisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups is considered. It is shown
that the role of Drinfeld's doubles play the complexifications of the
corresponding compact groups. These complex doubles are used to define the
natural actions of the isotropic subgroups forming the doubles on the group
manifolds of the N=2 superconformal WZNW models. The Poisson- Lie T-duality in
N=2 superconformal U(2)-WZNW model considered in details. It is shown that this
model admits Poisson-Lie symmetries with respect to the isotropic subgroups
forming Drinfeld's double Gl(2,C). Poisson-Lie T-duality transformation maps
this model into itself but acts nontrivialy on the space of classical
solutions. Supersymmetric generalization of Poisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups of higher dimensions is
proposed.Comment: 12 pages, latex, misprints correcte
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