About quantum fluctuations and holographic principle in (4+n)-dimensional spacetime

In the article we present explicit expressions for quantum fluctuations of spacetime in the case of $(4+n)$-dimensional spacetimes, and consider their holographic properties and some implications for clocks, black holes and computation. We also consider quantum fluctuations and their holographic properties in ADD model and estimate the typical size and mass of the clock to be used in precise measurements of spacetime fluctuations. Numerical estimations of phase incoherence of light from extra-galactic sources in ADD model are also presented.Comment: 5 page

Phonon-Assisted Gain in a Semiconductor Double Quantum Dot Maser

We develop a microscopic model for the recently demonstrated double quantum dot (DQD) maser. In characterizing the gain of this device we find that, in addition to the direct stimulated emission of photons, there is a large contribution from the simultaneous emission of a photon and a phonon, i.e., the phonon sideband. We show that this phonon-assisted gain typically dominates the overall gain which leads to masing. Recent experimental data are well fit with our model.Comment: v1: 6 pgs, 2 figures; v2: 6 pgs, 3 figures, added Fig 2b and Fig. 3b, modified main text; v3: 6+ pgs, 3 figures, modified main tex

Injection Locking of a Semiconductor Double Quantum Dot Micromaser

Emission linewidth is an important figure of merit for masers and lasers. We recently demonstrated a semiconductor double quantum dot (DQD) micromaser where photons are generated through single electron tunneling events. Charge noise directly couples to the DQD energy levels, resulting in a maser linewidth that is more than 100 times larger than the Schawlow-Townes prediction. Here we demonstrate a linewidth narrowing of more than a factor 10 by locking the DQD emission to a coherent tone that is injected to the input port of the cavity. We measure the injection locking range as a function of cavity input power and show that it is in agreement with the Adler equation. The position and amplitude of distortion sidebands that appear outside of the injection locking range are quantitatively examined. Our results show that this unconventional maser, which is impacted by strong charge noise and electron-phonon coupling, is well described by standard laser models

The role of the scale and the frequency bandwidth of steering wheel vibration on road surface recognition

Automobile drivers are regularly exposed to vibrational stimuli in their vehicle. Of the automobile subsystems, the steering wheel is one of the most important due to its role in controlling the vehicle. In particular, the steering wheel plays an important role in transmitting information about the road and about the vehicle to the driver. This paper investigates the effect of steering system feedback gain and steering system feedback bandwidth on the human interpretation of the driving information transmitted by the steering wheel. Human recognition of road surface type was found to be highly dependent on the feedback gain and the feedback bandwidth of the steering wheel vibration. The results provide some basic guidelines for designing the control logic of steer by wire systems

On symmetric commutator subgroups, braids, links and homotopy groups

In this paper, we investigate some applications of commutator subgroups to homotopy groups and geometric groups. In particular, we show that the intersection subgroups of some canonical subgroups in certain link groups modulo their symmetric commutator subgroups are isomorphic to the (higher) homotopy groups. This gives a connection between links and homotopy groups. Similar results hold for braid and surface groups.Comment: 24 pages, 1 figur

High-order harmonic generation from diatomic molecules with large internuclear distance: The effect of two-center interference

In the present paper, we investigate the high-order harmonic generation (HHG) from diatomic molecules with large internuclear distance using a strong field approximation (SFA) model. We find that the hump and dip structure emerges in the plateau region of the harmonic spectrum, and the location of this striking structure is sensitive to the laser intensity. Our model analysis reveals that two-center interference as well as the interference between different recombination electron trajectories are responsible for the unusual enhanced or suppressed harmonic yield at a certain order, and these interference effects are greatly influenced by the laser parameters such as intensity.Comment: 5 pages,4 figure