Graph-theory induced gravity and strongly-degenerate fermions in a self-consistent Einstein universe

We study UV-finite theory of induced gravity. We use scalar fields, Dirac fields and vector fields as matter fields whose one-loop effects induce the gravitational action. To obtain the mass spectrum which satisfies the UV-finiteness condition, we use a graph-based construction of mass matrices. The existence of a self-consistent static solution for an Einstein universe is shown in the presence of degenerate fermion.Comment: 16pages, 1figur

Robust Unconditionally Secure Quantum Key Distribution with Two Nonorthogonal and Uninformative States

We introduce a novel form of decoy-state technique to make the single-photon Bennett 1992 protocol robust against losses and noise of a communication channel. Two uninformative states are prepared by the transmitter in order to prevent the unambiguous state discrimination attack and improve the phase-error rate estimation. The presented method does not require strong reference pulses, additional electronics or extra detectors for its implementation.Comment: 7 pages, 2 figure

I=2 Two-Pion Wave Function and Scattering Phase Shift

We calculate a two-pion wave function for the I=2 $S$-wave two-pion system with a finite scattering momentum and estimate the interaction range between two pions, which allows us to examine the validity of a necessary condition for the finite size formula presented by Rummukainen and Gottlieb. We work in the quenched approximation employing the plaquette gauge action for gluons and the improved Wilson action for quarks at $1/a=1.63 {\rm GeV}$ on $32^3\times 120$ lattice. The quark masses are chosen to give $m_\pi = 0.420$, 0.488 and $0.587 {\rm GeV}$. We find that the energy dependence of the interaction range is small and the necessary condition is satisfied for our range of the quark mass and the scattering momentum, $k \le 0.16 {\rm GeV}$. We also find that the scattering phase shift can be obtained with a smaller statistical error from the two-pion wave function than from the two-pion time correlator.Comment: 23 pages, 7 figures, added a reference (Phys.Rev.D73:054503,2006) in v

Unconditionally Secure Key Distribution Based on Two Nonorthogonal States

We prove the unconditional security of the Bennett 1992 protocol, by using a reduction to an entanglement distillation protocol initiated by a local filtering process. The bit errors and the phase errors are correlated after the filtering, and we can bound the amount of phase errors from the observed bit errors by an estimation method involving nonorthogonal measurements. The angle between the two states shows a trade-off between accuracy of the estimation and robustness to noises.Comment: 5 pages, 1 figur

Quantum circuit for security proof of quantum key distribution without encryption of error syndrome and noisy processing

One of the simplest security proofs of quantum key distribution is based on the so-called complementarity scenario, which involves the complementarity control of an actual protocol and a virtual protocol [M. Koashi, e-print arXiv:0704.3661 (2007)]. The existing virtual protocol has a limitation in classical postprocessing, i.e., the syndrome for the error-correction step has to be encrypted. In this paper, we remove this limitation by constructing a quantum circuit for the virtual protocol. Moreover, our circuit with a shield system gives an intuitive proof of why adding noise to the sifted key increases the bit error rate threshold in the general case in which one of the parties does not possess a qubit. Thus, our circuit bridges the simple proof and the use of wider classes of classical postprocessing.Comment: 8 pages, 2 figures. Typo correcte

Near term measurements with 21 cm intensity mapping: neutral hydrogen fraction and BAO at z<2

It is shown that 21 cm intensity mapping could be used in the near term to make cosmologically useful measurements. Large scale structure could be detected using existing radio telescopes, or using prototypes for dedicated redshift survey telescopes. This would provide a measure of the mean neutral hydrogen density, using redshift space distortions to break the degeneracy with the linear bias. We find that with only 200 hours of observing time on the Green Bank Telescope, the neutral hydrogen density could be measured to 25% precision at redshift 0.54<z<1.09. This compares favourably to current measurements, uses independent techniques, and would settle the controversy over an important parameter which impacts galaxy formation studies. In addition, a 4000 hour survey would allow for the detection of baryon acoustic oscillations, giving a cosmological distance measure at 3.5% precision. These observation time requirements could be greatly reduced with the construction of multiple pixel receivers. Similar results are possible using prototypes for dedicated cylindrical telescopes on month time scales, or SKA pathfinder aperture arrays on day time scales. Such measurements promise to improve our understanding of these quantities while beating a path for future generations of hydrogen surveys.Comment: 6 pages, 5 figures. Submitted to Phys. Rev. D. Addressed reviewer comments. Changed figure format, added more detailed technical discussion, and added forecasts for aperture arrays. Added references

Addendum to "Classical and Quantum Evolutions of the de Sitter and the anti-de Sitter Universes in 2+1 dimensions"

The previous discussion \cite{ezawa} on reducing the phase space of the first order Einstein gravity in 2+1 dimensions is reconsidered. We construct a \lq\lq correct" physical phase space in the case of positive cosmological constant, taking into account the geometrical feature of SO(3,1) connections. A parametrization which unifies the two sectors of the physical phase space is also given.Comment: Latex 8 pages (Crucial and essential changes have been made.

Properties of Umbral Dots from Stray Light Corrected Hinode Filtergrams

High resolution blue continuum filtergrams from Hinode are employed to study the umbral fine structure of a regular unipolar sunspot. The removal of scattered light from the images increases the rms contrast by a factor of 1.45 on average. Improvement in image contrast renders identification of short filamentary structures resembling penumbrae that are well separated from the umbra-penumbra boundary and comprise bright filaments/grains flanking dark filaments. Such fine structures were recently detected from ground based telescopes and have now been observed with Hinode. A multi-level tracking algorithm was used to identify umbral dots in both the uncorrected and corrected images and to track them in time. The distribution of the values describing the photometric and geometric properties of umbral dots are more easily affected by the presence of stray light while it is less severe in the case of kinematic properties. Statistically, umbral dots exhibit a peak intensity, effective diameter, lifetime, horizontal speed and a trajectory length of 0.29 I_QS, 272 km, 8.4 min, 0.45 km/s and 221 km respectively. The 2 hr 20 min time sequence depicts several locations where umbral dots tend to appear and disappear repeatedly with various time intervals. The correction for scattered light in the Hinode filtergrams facilitates photometry of umbral fine structure which can be related to results obtained from larger telescopes and numerical simulations.Comment: Accepted for publication in ApJ : 10 pages, 10 figures, 3 table