18,408 research outputs found
On the anomaly of nonlocal symmetry in the chiral QED
We show that the anomaly of nonlocal symmetry can be canceled by the
well-known Wess-Zumino acton which cancels the gauge anomaly in the
two-dimensional chiral electrodynamics.Comment: 4 pages, latex, no figure
Quantum Key Distribution with Blind Polarization Bases
We propose a new quantum key distribution scheme that uses the blind
polarization basis. In our scheme the sender and the receiver share key
information by exchanging qubits with arbitrary polarization angles without
basis reconciliation. As only random polarizations are transmitted, our
protocol is secure even when a key is embedded in a not-so-weak coherent-state
pulse. We show its security against the photon number splitting attack and the
impersonation attack.Comment: Security has been improved upon referee's comment. 4 pages and 2
figure
Simultaneous dual-frequency radio observations of S5 0716+714: A search for intraday variability with the Korean VLBI Network
This study aims to search for the existence of intraday variability (IDV) of
BL Lac object S5 0716+714 at high radio frequencies for which the interstellar
scintillation effect is not significant. Using the 21-meter radio telescope of
the Korean VLBI Network (KVN), we present results of multi-epoch simultaneous
dual-frequency radio observations. Single-dish observations of S5 0716+714 were
simultaneously conducted at 21.7 GHz (K-band) and 42.4 GHz (Q-band), with a
high cadence of 30-60 minute intervals.We observed four epochs between December
2009 and June 2010. Over the whole set of observation epochs, S5 0716+714
showed significant inter-month variations in flux density at both the K- and
Q-bands, with modulation indices of approximately 19% for the K-band and
approximately 36% for the Q-band. In all epochs, no clear intraday variability
was detected at either frequency. The source shows monotonic flux density
increase in epochs 1 and 3 and monotonic flux density decrease in epochs 2 and
4. In the flux density increasing phases, the flux densities at the Q-band
increase more rapidly. In the decreasing phase, no significant flux density
difference is seen at the two frequencies. The situation could be different
close to flux density peaks that we did not witness in our observations. We
find an inverted spectrum with mean spectral indices of -0.57+-0.13 in epoch 1
and -0.15+-0.11 in epoch 3. On the other hand, we find relatively steep indices
of +0.24+-0.14 and +0.17+-0.18 in epochs 2 and 4, respectively. We conclude
that the frequency dependence of the variability and the change of the spectral
index are caused by source-intrinsic effects rather than by any extrinsic
scintillation effect.Comment: 6 pages and 4 figures and 4 table
- …