Criticality of natural absorbing states

We study a recently introduced ladder model which undergoes a transition between an active and an infinitely degenerate absorbing phase. In some cases the critical behaviour of the model is the same as that of the branching annihilating random walk with $N\geq 2$ species both with and without hard-core interaction. We show that certain static characteristics of the so-called natural absorbing states develop power law singularities which signal the approach of the critical point. These results are also explained using random walk arguments. In addition to that we show that when dynamics of our model is considered as a minimum finding procedure, it has the best efficiency very close to the critical point.Comment: 6 page

Flow field and performance of high frequency micromachined synthetic jets

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77283/1/AIAA-2002-974-315.pd

Numerical simulation of micromachined acoustic resonators

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/76479/1/AIAA-2000-546-400.pd

Spectroscopy of the circumplanetary disk around the young planet-mass companion CT Cha b

Several planet-mass companions (PMCs) on wide-orbits have been imaged around young stars (1-10 Myr). Their estimated mass is just around the brown dwarf to giant planet transition (~13 Jupiter masses), which makes them especially interesting for both star and planet formation theories. Several formation scenarios exist, but none of them can explain all properties of the currently known PMCs. There are strong theoretical reasons to expect disks around PMCs, and indirect evidence for disks around PMCs from optical and near-infrared emission exists. However, attempts to detect the dust and gas emission of the disk directly have been unsuccessful. The high sensitivity of JWST MIRI will allow detecting disks with sizes smaller than one au, masses as low 1/10000 of a Jupiter mass and will provide first constraints on the solid and gas composition of disks around PMCs. We propose to observe the PMC CT Cha b with the MIRI spectrograph to detect the dust and gas emission (water lines) of its disk. Those results allow for a comparison to the composition of the primary disk of CT Cha, which is observed simultaneously, and to observations of protoplanetary disks, providing new constraints for possible differences in disk evolution. Those observations, together with forthcoming complementary ALMA observations, will put stringent limits on the mass and size of the companion's disk; quantities most relevant for PMC formation theories and spin-evolution studies. The proposed program will be a big step forward for our understanding of the mysterious nature of wide-orbit planet-mass companions and will serve as a pioneering study for future JWST surveys of PMCs

Dual-probe decoherence microscopy: Probing pockets of coherence in a decohering environment

We study the use of a pair of qubits as a decoherence probe of a non-trivial environment. This dual-probe configuration is modelled by three two-level-systems which are coupled in a chain in which the middle system represents an environmental two-level-system (TLS). This TLS resides within the environment of the qubits and therefore its coupling to perturbing fluctuations (i.e. its decoherence) is assumed much stronger than the decoherence acting on the probe qubits. We study the evolution of such a tripartite system including the appearance of a decoherence-free state (dark state) and non-Markovian behaviour. We find that all parameters of this TLS can be obtained from measurements of one of the probe qubits. Furthermore we show the advantages of two qubits in probing environments and the new dynamics imposed by a TLS which couples to two qubits at once.Comment: 29 pages, 10 figure

Flow structure and performance of axisymmetric synthetic jets

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/77189/1/AIAA-2001-1008-312.pd

Bundles over Nearly-Kahler Homogeneous Spaces in Heterotic String Theory

We construct heterotic vacua based on six-dimensional nearly-Kahler homogeneous manifolds and non-trivial vector bundles thereon. Our examples are based on three specific group coset spaces. It is shown how to construct line bundles over these spaces, compute their properties and build up vector bundles consistent with supersymmetry and anomaly cancelation. It turns out that the most interesting coset is $SU(3)/U(1)^2$. This space supports a large number of vector bundles which lead to consistent heterotic vacua, some of them with three chiral families.Comment: 32 pages, reference adde