In order to expand the astrophysical reach of gravitational wave (GW) detectors, several
interferometer topologies have been proposed, in the past, to evade the thermodynamic
and quantum mechanical limits in future detectors. In this work, we make a systematic
comparison among these topologies by considering their sensitivities and complexities.
We numerically optimize their sensitivities by introducing a cost function that tries
to maximize the broadband improvement over the sensitivity of current detectors. We
find that frequency-dependent squeezed-light injection with a 100 m scale filter cavity
yields a good broadband sensitivity, with low complexity, and good robustness against
optical loss. This study gives us a guideline for the near-term experimental research
programs in enhancing the performance of future GW detectors. (paper)$$$$
Some mathematical problems connected with the numerical solving of equations of motion
for charged particles in inhomogeneous magnetic fields are considered. The three-dimensional
spline approximation of the magnetic field is proposed. This allows one to use high-accuracy
numerical methods to evaluate the trajectory of the moving charged particle in inhomogeneous
magnetic field. On the base of multidimensional approximation the fast algorithms
for the description of equations of motion solution and its derivatives with respect
to initial data are proposed. The application of the considered methods for ALICE
experiment are demonstrated. (author)$$$$
This paper investigates the use of two different methods, the optical and the computer-aided
diffraction-grating spectrometer, to measure the wavelength of visible lines of Balmer
series from the hydrogen atomic spectrum and estimate the value of Rydberg's constant.
Analysis and interpretation of data showed that both methods, despite their difference
in terms of the type of equipment used, displayed good performance in terms of precision
of measurements of wavelengths of spectral lines. A comparison was carried out between
the experimental value of Rydberg's constant obtained with both methods and the accepted
value. The results of Rydberg's constant obtained with both the optical and computer-aided
spectrometers were 1.099 28 × 10^{−7} m^{−1} and 1.095 13 × 10^{−7} m^{−1} with
an error difference of 0.17% and 0.20% compared to the accepted value 1.097 373 × 10^{−7} m^{−1},
respectively. (paper)$$$$
We establish a correspondence between classical A_{n}^{(1)} affine
Toda field theories and A_{n} Bethe ansatz systems. We show that the connection
coefficients relating specific solutions of the associated classical linear problem
satisfy functional relations of the type that appear in the context of the massive
quantum integrable model. (paper)$$$$
We experimentally demonstrate a novel nanoscale temperature sensing technique that
is based on single atomic defects in diamonds, namely nitrogen vacancy color centers.
Sample sizes range from millimeter down to a few tens of nanometers. In particular
nanodiamonds were used as dispersed probes to acquire spatially resolved temperature
profiles utilizing the sensitivity of the optically accessible electron spin level
structure we achieve a temperature noise floor of 5mK/Mhz for bulk diamond and 130mK/Mhz
for nanodiamonds and accuracies of 1mK. To this end we have developed a new decoupling
technique in order to suppress to otherwise limiting effect of magnetic field fluctuations.
In addition, high purity isotopically enriched 12C artificial diamonds is used. The
high sensitivity to temperature changes adds to the well studied sensitivities to
magnetic and electric fields and makes NV diamond a multipurpose nanoprobe. (author)$$$$
Recent developments in the theory of plasma-based collisionally excited x-ray lasers
(XRL) have shown an optimization potential based on the dependence of the absorption
region of the pumping laser on its angle of incidence on the plasma. For the experimental
proof of this idea, a number of diagnostic schemes were developed, tested, qualified
and applied. A high-resolution imaging system, yielding the keV emission profile perpendicular
to the target surface, provided positions of the hottest plasma regions, interesting
for the benchmarking of plasma simulation codes. The implementation of a highly efficient
spectrometer for the plasma emission made it possible to gain information about the
abundance of the ionization states necessary for the laser action in the plasma. The
intensity distribution and deflection angle of the pump laser beam could be imaged
for single XRL shots, giving access to its refraction process within the plasma. During
a European collaboration campaign at the Lund Laser Center, Sweden, the optimization
of the pumping laser incidence angle resulted in a reduction of the required pumping
energy for a Ni-like Mo XRL, which enabled the operation at a repetition rate of 10
Hz. Using the experiences gained there, the XRL performance at the PHELIX facility,
GSI Darmstadt with respect to achievable repetition rate and at wavelengths below
20 nm was significantly improved, and also important information for the development
towards multi-100 eV plasma XRLs was acquired. Due to the setup improvements achieved
during the work for this thesis, the PHELIX XRL system now has reached a degree of
reproducibility and versatility which is sufficient for demanding applications like
the XRL spectroscopy of heavy ions. In addition, a European research campaign, aiming
towards plasma XRLs approaching the water-window (wavelengths below 5 nm) was initiated.
(orig.)$$$$
The present doctoral thesis describes experimentally measured properties of the resonance
spectra of flat microwave billiards with partially broken timereversal invariance
induced by an embedded magnetized ferrite. A vector network analyzer determines the
complex scattering matrix elements. The data is interpreted in terms of the scattering
formalism developed in nuclear physics. At low excitation frequencies the scattering
matrix displays isolated resonances. At these the effect of the ferrite on isolated
resonances (singlets) and pairs of nearly degenerate resonances (doublets) is investigated.
The hallmark of time-reversal symmetry breaking is the violation of reciprocity, i.e.
of the symmetry of the scattering matrix. One finds that reciprocity holds in singlets;
it is violated in doublets. This is modeled by an effective Hamiltonian of the resonator.
A comparison of the model to the data yields time-reversal symmetry breaking matrix
elements in the order of the level spacing. Their dependence on the magnetization
of the ferrite is understood in terms of its magnetic properties. At higher excitation
frequencies the resonances overlap and the scattering matrix elements fluctuate irregularly
(Ericson fluctuations). They are analyzed in terms of correlation functions. The data
are compared to three models based on random matrix theory. The model by Verbaarschot,
Weidenmueller and Zirnbauer describes time-reversal invariant scattering processes.
The one by Fyodorov, Savin and Sommers achieves the same for systems with complete
time-reversal symmetry breaking. An extended model has been developed that accounts
for partial breaking of time-reversal invariance. This extended model is in general
agreement with the data, while the applicability of the other two models is limited.
The cross-correlation function between forward and backward reactions determines the
time-reversal symmetry breaking matrix elements of the Hamiltonian to up to 0.3 mean
level spacings. Finally the sensitivity of the elastic enhancement factor to time-reversal
symmetry breaking is studied. Based on the data elastic enhancement factors below
2 are found which is consistent with breaking of time-reversal invariance in the regime
of overlapping resonances. The present work provides the framework to probe for broken
time-reversal invariance in any scattering data by a multitude of methods in the whole
range between isolated and overlapping resonances. (orig.)$$$$
Molecular dynamics for fermions by Feldmeier, H. (Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany)); Schnack,
J. (Osnabrueck Univ. (Germany). Fachbereich Physik); Gesellschaft fuer Schwerionenforschung mbH, Darmstadt (Germany) Read MoreCollapse
[en]
The time-dependent variational principle for many-body trial states is used to discuss
the relation between the approaches of different molecular dynamics models to describe
indistinguishable fermions. Early attempts to include effects of the Pauli principle
by means of nonlocal potentials as well as more recent models which work with antisymmetrized
many-body states are reviewed under these premises. (orig.)$$$$
The time evolution of plasma potential has been measured with a retarding field analyzer
in pulsed operation mode with electron cyclotron resonance ion sources at JYFL and
RIKEN. Three different ion sources with microwave frequencies ranging from 6.4 to
18 GHz were employed for the experiments. The plasma potential was observed to increase
10-75 % during the Pre-glow and 10-30 % during the afterglow compared to steady state.
The paper is followed by the slides of the presentation. (authors)$$$$
A quantum system is quasi-exactly solvable (QES) when a subset of its eigenvalues
can be obtained in closed form, or they are the roots of closed form expressions.
In one dimension, QES states assume the form Ψ(x)=P(x)R(x), involving a known positive
reference function R(x) and a polynomial P(x), so that the Taylor expansion of Ψ(x)/R(x)
truncates at a finite order. For non-QES states this truncation procedure, for suitable
reference functions, can provide approximate values for the eigenvalues. It corresponds
to the Hill determinant method, which is known to be unstable when R assumes the controlling
asymptotic form of the physical state. For this reason, it cannot be used to simultaneously
generate exact QES states while approximating non-QES states. To address these limitations,
the orthogonal polynomial projection quantization (OPPQ) method was developed (Handy
and Vrinceanu 2013 J. Phys. A: Math. Theor. 46 135202; 2013 J. Phys. B: Atom. Mol.
Opt. Phys. 46 115002). It is demonstrated in this paper that OPPQ can directly and
transparently provide, at the same time, both algebraic solutions for QES states and
convergent, numerically stable, approximations for non-QES states. Within the OPPQ
analysis for the wavefunction representation Φ(x)=R(x)Φ(x), the Bender–Dunne energy
orthogonal polynomials correspond, exactly (up to a numerical factor), to the energy
dependent power moments ν(p) = ∫dx x^{p}Φ(x). Within this perspective, the
existence of QES states is associated with an anomalous kink behavior in the order
of the finite difference moment equation corresponding to the ν's, suggesting a change
in the number of degrees of freedom. This was first noted through the implementation
of the eigenvalue moment method, the first application of semidefinite programming
analysis to quantum operators (Handy and Bessis 1985 Phys. Rev. Lett. 55 931). This
moments' perspective also reveals additional properties for the non-QES states of
the same symmetry as the QES states: their lower order ν-moments must be zero. We
demonstrate our results in the context of the two sextic potentials: V_{sa}(x)
= x^{6} + mx^{2} + bx^{4} and V_{ss}(x) = x^{6}
+ mx^{2} + b/x^{2}. (paper)$$$$