The state space of short-range Ising spin glasses: the density of states

The state space of finite square and cubic Ising spin glass models is analysed in terms of the global and the local density of states. Systems with uniform and gaussian probability distribution of interactions are compared. Different measures for the local state density are presented and discussed. In particular the question whether the local density of states grows exponentially or not is considered. The direct comparison of global and local densities leads to consequences for the structure of the state space.Comment: 18 pages (including 6 figures); submitted to Z.f.Physik

A Review of the Biology, Ecology and Behavior of Velvety Tree Ants of North America

Ants belonging to the genus Liometopum are regionally distributed across North America, Europe and Asia. L. apiculatum Mayr, L. luctuosum Wheeler, and L. occidentale Emery are found in western North America and are referred to as velvety tree ants. Very little is known about the biology of these species, but they are similar. They are typically associated with trees and shrubs and are frequently found tending hemipterans. All three species are are easily disturbed and and resort to highly aggressive behaviors including the use of strong alarm odors. The following review is intended to summarize the literature regarding the biology and control of these species. Special emphasis has been given to factors that might be important in their control and gaps in our current knowledge

A Review of the Biology, Ecology and Behavior of Velvety Tree Ants of North America

Ants belonging to the genus Liometopum are regionally distributed across North America, Europe and Asia. L. apiculatum Mayr, L. luctuosum Wheeler, and L. occidentale Emery are found in western North America and are referred to as velvety tree ants. Very little is known about the biology of these species, but they are similar. They are typically associated with trees and shrubs and are frequently found tending hemipterans. All three species are are easily disturbed and and resort to highly aggressive behaviors including the use of strong alarm odors. The following review is intended to summarize the literature regarding the biology and control of these species. Special emphasis has been given to factors that might be important in their control and gaps in our current knowledge.</span

Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots

We report on the development and testing of a coplanar stripline antenna that is designed for integration in a magneto-photoluminescence experiment to allow coherent control of individual electron spins confined in single self-assembled semiconductor quantum dots. We discuss the design criteria for such a structure which is multi-functional in the sense that it serves not only as microwave delivery but also as electrical top gate and shadow mask for the single quantum dot spectroscopy. We present test measurements on hydrogenated amorphous silicon, demonstrating electrically detected magnetic resonance using the in-plane component of the oscillating magnetic field created by the coplanar stripline antenna necessary due to the particular geometry of the quantum dot spectroscopy. From reference measurements using a commercial electron spin resonance setup in combination with finite element calculations simulating the field distribution in the structure, we obtain an average magnetic field of ~0.2mT at the position where the quantum dots would be integrated into the device. The corresponding pi-pulse time of ~0.3us fully meets the requirements set by the high sensitivity optical spin read-out scheme developed for the quantum dot

Quasi-two-dimensional Fermi surfaces of the heavy-fermion superconductor Ce2_2PdIn8_8

We report low-temperature de Haas-van Alphen (dHvA) effect measurements in magnetic fields up to 35 T of the heavy-fermion superconductor Ce$_2$PdIn$_8$. The comparison of the experimental results with band-structure calculations implies that the 4$f$ electrons are itinerant rather than localized. The cyclotron masses estimated at high field are only moderately enhanced, 8 and 14 $m_0$, but are substantially larger than the corresponding band masses. The observed angular dependence of the dHvA frequencies suggests quasi-two-dimensional Fermi surfaces in agreement with band-structure calculations. However, the deviation from ideal two dimensionality is larger than in CeCoIn$_5$, with which Ce$_2$PdIn$_8$ bears a lot of similarities. This subtle distinction accounts for the different superconducting critical temperatures of the two compounds.Comment: accepted to Phys. Rev.

The historical vanishing of the Blazhko effect of RR Lyr from GEOS and Kepler surveys

RR Lyr is one of the most studied variable stars. Its light curve has been regularly monitored since the discovery of the periodic variability in 1899. Analysis of all observed maxima allows us to identify two primary pulsation states defined as pulsation over a long (P0 longer than 0.56684 d) and a short (P0 shorter than 0.56682 d) primary pulsation period. These states alternate with intervals of 13-16 yr, and are well defined after 1943. The 40.8 d periodical modulations of the amplitude and the period (i.e. Blazhko effect) were noticed in 1916. We provide homogeneous determinations of the Blazhko period in the different primary pulsation states. The Blazhko period does not follow the variations of P0 and suddenly diminished from 40.8 d to around 39.0 d in 1975. The monitoring of these periodicities deserved and deserves a continuous and intensive observational effort. For this purpose we have built dedicated, transportable and autonomous small instruments, Very Tiny Telescopes (VTTs), to observe the times of maximum brightness of RR Lyr. As immediate results the VTTs recorded the last change of P0 state in mid-2009 and extended the time coverage of the Kepler observations, thus recording a maximum O-C amplitude of the Blazhko effect at the end of 2008, followed by the historically smallest O-C amplitude in late 2013. This decrease is still ongoing and VTT instruments are ready to monitor the expected increase in the next few years.Comment: 10 pages, 6 figures. Accepted for publication in MNRAS. Contents of appendix B may be requested to first autho

A new method for analyzing ground-state landscapes: ballistic search

A ``ballistic-search'' algorithm is presented which allows the identification of clusters (or funnels) of ground states in Ising spin glasses even for moderate system sizes. The clusters are defined to be sets of states, which are connected in state-space by chains of zero-energy flips of spins. The technique can also be used to estimate the sizes of such clusters. The performance of the method is tested with respect to different system sizes and choices of parameters. As an application the ground-state funnel structure of two-dimensional +or- J spin glasses of systems up to size L=20 is analyzed by calculating a huge number of ground states per realization. A T=0 entropy per spin of s_0=0.086(4)k_B is obtained.Comment: 10 pages, 11 figures, 35 references, revte