12,635 research outputs found
A low-temperature dynamic mode scanning force microscope operating in high magnetic fields
A scanning force microscope was implemented operating at temperatures below
4.2K and in magnetic fields up to 8T. Piezoelectric quartz tuning forks were
employed for non optical tip-sample distance control in the dynamic operation
mode. Fast response was achieved by using a phase-locked loop for driving the
mechanical oscillator. Possible applications of this setup for various scanning
probe techniques are discussed.Comment: 5 pages, 5 figures, submitted to "Review of Scientific Instruments
One-loop corrections to gaugino (co-)annihilation into quarks in the MSSM
We present the full supersymmetric QCD corrections
for gaugino annihilation and co-annihilation into light and heavy quarks in the
Minimal Supersymmetric Standard Model (MSSM). We demonstrate that these
channels are phenomenologically relevant within the so-called phenomenological
MSSM. We discuss selected technical details such as the dipole subtraction
method in the case of light quarks and the treatment of the bottom quark mass
and Yukawa coupling. Numerical results for the (co-)annihilation cross sections
and the predicted neutralino relic density are presented. We show that the
impact of including the radiative corrections on the cosmologically preferred
region of the parameter space is larger than the current experimental
uncertainty from Planck data.Comment: 19 pages, 9 figures. Matches version published in Phys.Rev.
Discrete Fracture Model with Anisotropic Load Sharing
A two-dimensional fracture model where the interaction among elements is
modeled by an anisotropic stress-transfer function is presented. The influence
of anisotropy on the macroscopic properties of the samples is clarified, by
interpolating between several limiting cases of load sharing. Furthermore, the
critical stress and the distribution of failure avalanches are obtained
numerically for different values of the anisotropy parameter and as a
function of the interaction exponent . From numerical results, one can
certainly conclude that the anisotropy does not change the crossover point
in 2D. Hence, in the limit of infinite system size, the crossover
value between local and global load sharing is the same as the one
obtained in the isotropic case. In the case of finite systems, however, for
, the global load sharing behavior is approached very slowly
Precision predictions for supersymmetric dark matter
The dark matter relic density has been measured by Planck and its
predecessors with an accuracy of about 2%. We present theoretical calculations
with the numerical program DM@NLO in next-to-leading order SUSY QCD and beyond,
which allow to reach this precision for gaugino and squark (co-)annihilations,
and use them to scan the phenomenological MSSM for viable regions, applying
also low-energy, electroweak and hadron collider constraints.Comment: 6 pages, 1 table, 8 figures, proceedings of ICHEP 201
Infrared spectroscopy of diatomic molecules - a fractional calculus approach
The eigenvalue spectrum of the fractional quantum harmonic oscillator is
calculated numerically solving the fractional Schr\"odinger equation based on
the Riemann and Caputo definition of a fractional derivative. The fractional
approach allows a smooth transition between vibrational and rotational type
spectra, which is shown to be an appropriate tool to analyze IR spectra of
diatomic molecules.Comment: revised + extended version, 9 pages, 6 figure
Operation characteristics of piezoelectric quartz tuning forks in high magnetic fields at liquid helium temperatures
Piezoelectric quartz tuning forks are investigated in view of their use as
force sensors in dynamic mode scanning probe microscopy at temperatures down to
1.5 K and in magnetic fields up to 8 T. The mechanical properties of the forks
are extracted from the frequency dependent admittance and simultaneous
interferometric measurements. The performance of the forks in a cryogenic
environment is investigated. Force-distance studies performed with these
sensors at low temperatures are presented
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