21,441 research outputs found
Fixed subgroups are compressed in surface groups
For a compact surface (orientable or not, and with boundary or not)
we show that the fixed subgroup, , of any family of
endomorphisms of is compressed in i.e.,
for
any subgroup . On the way, we
give a partial positive solution to the inertia conjecture, both for free and
for surface groups. We also investigate direct products, , of finitely many
free and surface groups, and give a characterization of when satisfies that
for
every
No-cloning theorem in thermofield dynamics
We discuss the relation between the no-cloning theorem from quantum
information and the doubling procedure used in the formalism of thermofield
dynamics (TFD). We also discuss how to apply the no-cloning theorem in the
context of thermofield states defined in TFD. Consequences associated to mixed
states, von Neumann entropy and thermofield vacuum are also addressed.Comment: 16 pages, 3 figure
Minimizing boundary layer bleed for a mixed compression inlet
An experimental investigation of a full scale mixed compression inlet sized for the TF30-P-3 turbofan engine was conducted at Mach 2.5 and 2.0 operating conditions. The two cone axisymmetric inlet had minimum internal contraction consistent with high total pressure recovery and low cowl drag. At Mach 2.5, inlet recovery exceeded 0.90 with only 0.02 centerbody bleed mass-flow ratio and zero cowl bleed. A centerbody bleed of approximately 0.05 gave a maximum inlet unstart angle-of-attack of 6.85 deg. Inlet performance and angle-of-attack tolerance is presented for operation at Mach 2.5 and 2.0
Enhanced energy relaxation process of quantum memory coupled with a superconducting qubit
For quantum information processing, each physical system has different
advantage for the implementation and so hybrid systems to benefit from several
systems would be able to provide a promising approach. One of the common hybrid
approach is to combine a superconducting qubit as a controllable qubit and the
other quantum system with a long coherence time as a memory qubit. The
superconducting qubit allows us to have an excellent controllability of the
quantum states and the memory qubit is capable of storing the information for a
long time. By tuning the energy splitting between the superconducting qubit and
the memory qubit, it is believed that one can realize a selective coupling
between them. However, we have shown that this approach has a fundamental
drawback concerning energy leakage from the memory qubit. The detuned
superconducting qubit is usually affected by severe decoherence, and this
causes an incoherent energy relaxation from the memory qubit to the
superconducting qubit via the imperfect decoupling. We have also found that
this energy transport can be interpreted as an appearance of anti quantum Zeno
effect induced by the fluctuation in the superconducting qubit. We also discuss
a possible solution to avoid such energy relaxation process, which is feasible
with existing technology
Distortion in a full-scale bicone inlet with internal focused compression and 45 percent internal contraction
The distortion characteristics were investigated at the subsonic diffuser exit of a full-scale, Mach 2.5, axisymmetric, mixed compression inlet. Performance and steady-state distortion characteristics were obtained at zero and maximum angle of attack and during an inlet unstart-restart sequence. For the configuration with no cowl bleed, steady-state distortion P(max)P(min)P(bar) ranged from 0.10 for critical inlet operation at 0 deg angle-of-attack to 0.306 for supercritical inlet operation at 6.84 deg angle-of-attack. Vortex generators provided a 50 percent reduction in steady-state distortion for critical operation. Bleed has a smaller effect on steady-stated distortion
Performance of vortex generators in a Mach 2.5 low-bleed full scale 45-percent-internal-contraction axisymmetric inlet
Steady-state and dynamic flow characteristics associated with two sets of vortex generators having different mixing criteria were determined. The inlet performance with and without these vortex generators is presented. The vortex generators were successful in eliminating separation, increasing area-weighted total pressure recovery, and decreasing distortion. Transmission times obtained from cross-correlations of the wall static pressures and the diffuser exit total pressure showed no effect of the upstream flow characteristics on the diffuser exit pressures when generators were used. Without generators, separation occurred and the upstream pressure characteristics had immediate effects on the diffuser exit pressure characteristics
Boundary layer bleed system study for a full-scale, mixed-compression inlet with 45 percent internal contraction
The results of an experimental bleed development study for a full-scale, Mach 2.5, axisymmetric, mixed-compression inlet were presented. The inlet was designed to satisfy the airflow requirements of the TF30-P-3 turbofan engine. Capabilities for porous bleed on the cowl surface and ram-scoop/flush-slot bleed on the centerbody were provided. A configuration with no bleed on the cowl achieved a minimum stable, diffuser exit, total pressure recovery of 0.894 with a centerbody-bleed mass flow ratio of 0.02. Configurations with cowl bleed had minimum stable recoveries as high as 0.900 but suffered range decrement penalties from the increased bleed mass flow removal. Limited inlet stability and unstart angle-of-attack data are presented
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