Is blindsight possible under signal detection theory? Comment on Phillips (2021).

Phillips argues that blindsight is due to response criterion artifacts under degraded conscious vision. His view provides alternative explanations for some studies, but may not work well when one considers several key findings in conjunction. Empirically, not all criterion effects are decidedly nonperceptual. Awareness is not completely abolished for some stimuli, in some patients. But in other cases, it is clearly impaired relative to the corresponding visual sensitivity. This relative dissociation is what makes blindsight so important and interesting. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Transport in anisotropic model systems analyzed by a correlated projection superoperator technique.

By using a correlated projection operator, the time-convolutionless (TCL) method to derive a quantum master equation can be utilized to investigate the transport behavior of quantum systems as well. Here, we analyze a three-dimensional anisotropic quantum model system according to this technique. The system consists of Heisenberg coupled two-level systems in one direction and weak random interactions in all other ones. Depending on the partition chosen, we obtain ballistic behavior along the chains and normal transport in the perpendicular direction. These results are perfectly confirmed by the numerical solution of the full time-dependent Schrödinger equation.

Modeling heat transport through completely positive maps.

We investigate heat transport in a spin-1/2 Heisenberg chain, coupled locally to independent thermal baths of different temperature. The analysis is carried out within the framework of the theory of open systems by means of appropriate quantum master equations. The standard microscopic derivation of the weak-coupling Lindblad equation in the secular approximation is considered, and shown to be inadequate for the description of stationary nonequilibrium properties like a nonvanishing energy current. Furthermore, we derive an alternative master equation that is capable of describing a stationary energy current and, at the same time, leads to a completely positive dynamical map. This paves the way for efficient numerical investigations of heat transport in larger systems based on Monte Carlo wave function techniques.

Driven spin systems as quantum thermodynamic machines: fundamental limits.

We show that coupled two-level systems like qubits studied in quantum-information processing can be used as a thermodynamic machine. At least three qubits or spins are necessary and they must be arranged in a chain. The system is interfaced between two split baths and the working spin in the middle is externally driven. The machine performs Carnot-type cycles and is able to work as a heat pump or engine depending on the temperature difference of the baths, DeltaT , and the energy difference in the spin system, DeltaE . It can be shown that the efficiency is a function of DeltaT and DeltaE .

Application of the Hilbert space average method on heat conduction models.

We analyze closed one-dimensional chains of weakly coupled many level systems, by means of the so-called Hilbert space average method (HAM). Subject to some concrete conditions on the Hamiltonian of the system, our theory predicts energy diffusion with respect to a coarse-grained description for almost all initial states. Close to the respective equilibrium, we investigate this behavior in terms of heat transport and derive the heat conduction coefficient. Thus, we are able to show that both heat (energy) diffusive behavior as well as Fourier's law follows from and is compatible with a reversible Schrödinger dynamics on the complete level of description.

Non-Markovian quantum dynamics: correlated projection superoperators and Hilbert space averaging.

The time-convolutionless (TCL) projection operator technique allows a systematic analysis of the non-Markovian quantum dynamics of open systems. We present a class of projection superoperators that project the states of the total system onto certain correlated system-environment states. It is shown that the application of the TCL technique to this class of correlated superoperators enables the nonperturbative treatment of the dynamics of system-environment models for which the standard approach fails in any finite order of the coupling strength. We demonstrate further that the correlated superoperators correspond to the idea of a best guess of conditional quantum expectations, which is determined by a suitable Hilbert-space average. The general approach is illustrated by means of the model of a spin that interacts through randomly distributed couplings with a finite reservoir consisting of two energy bands. Extensive numerical simulations of the full Schrödinger equation of the model reveal the power and efficiency of the method.

Fourier's law from Schrödinger dynamics.

We consider a class of one-dimensional chains of weakly coupled many level systems. We present a theory which predicts energy diffusion within these chains for almost all initial states, if some concrete conditions on their Hamiltonians are met. By numerically solving the time dependent Schrödinger equation, we verify this prediction. Close to equilibrium we analyze this behavior in terms of heat conduction and compute the respective coefficient directly from the theory.

Global and local relaxation of a spin chain under exact Schrödinger and master-equation dynamics.

We solve the Schrödinger equation for an interacting spin chain locally coupled to a quantum environment with a specific degeneracy structure. The reduced dynamics of the whole spin chain as well as of single spins is analyzed. We show that the total spin chain relaxes to a thermal equilibrium state independently of the internal interaction strength. In contrast, the asymptotic states of each individual spin are thermal for weak but nonthermal for stronger spin-spin coupling. The transition between both scenarios is found for couplings of the order of 0.1 x deltaE , with deltaE denoting the Zeeman splitting. We compare these results with a master-equation treatment; when time averaged, both approaches lead to the same asymptotic state and finally with analytical results.

Temporary disturbances of the QT interval precede the onset of ventricular tachyarrhythmias in patients with structural heart diseases.

An increase in sinus rate prior to ventricular tachyarrhythmias has been demonstrated in previous studies. There is no clear data available concerning changes in ventricular de- and repolarization prior to ventricular tachyarrhythmias, especially in patients with structural heart disease. Therefore, the aim of this study was to analyze the QT and QTc interval (Bazett's formula immediately before the onset of ventricular tachyarrhythmias in stored electrograms of patients with ICDs. The study analyzed 228 spontaneous ventricular tachyarrhythmia episodes in 52 patients (mean age 64 +/- 10 years, 49 men, 3 women) and compared them with 146 electrograms of baseline rhythm recorded during regular ICD follow-up. Mean ventricular cycle length (CL), QT interval, and QTc were measured before the onset of ventricular tachyarrhythmia and during baseline rhythm. Prior to ventricular tachyarrhythmias onset, CL was significantly shorter than during baseline rhythm (714 +/- 139 vs 828 +/- 149 ms, P < 0.0001). By contrast, the QT interval (430 +/- 67 ms) and QTc interval (518 +/- 67 ms) were significantly prolonged before the onset of ventricular tachyarrhythmias as compared to baseline rhythm (QT 406 +/- 67 ms, QTc 450 +/- 61 ms; P < 0.0001). CL, QT, and QTc changes were independent of concomitant treatment with antiarrhythmic drugs. Ventricular tachyarrhythmias are preceded by a significant prolongation of the QT and QTc intervals. This phenomenon may represent a greater than normal disparity of repolarization recovery times possibly facilitating the development of ventricular tachyarrhythmias.