1,147,283 research outputs found
A Robust Image Hashing Algorithm Resistant Against Geometrical Attacks
This paper proposes a robust image hashing method which is robust against common image processing attacks and geometric distortion attacks. In order to resist against geometric attacks, the log-polar mapping (LPM) and contourlet transform are employed to obtain the low frequency sub-band image. Then the sub-band image is divided into some non-overlapping blocks, and low and middle frequency coefficients are selected from each block after discrete cosine transform. The singular value decomposition (SVD) is applied in each block to obtain the first digit of the maximum singular value. Finally, the features are scrambled and quantized as the safe hash bits. Experimental results show that the algorithm is not only resistant against common image processing attacks and geometric distortion attacks, but also discriminative to content changes
On significance of VLBI/Gaia position offsets
We have cross matched the Gaia Data Release 1 secondary dataset that contains
positions of 1.14 billion objects against the most complete to date catalogue
of VLBI positions of 11.4 thousand sources, almost exclusively active galactic
nuclei. We found 6,064 matches, i.e. 53% radio objects. The median uncertainty
of VLBI positions is a factor of 4 smaller than the median uncertainties of
their optical counterparts. Our analysis shows that the distribution of
normalized arc lengths significantly deviates from Rayleigh shape with an
excess of objects with small normalized arc lengths and with a number of
outliers. We found that 6% matches have radio optical offsets significant at
99% confidence level. Therefore, we conclude there exists a population of
objects with genuine offsets between centroids of radio and optical emission.Comment: 6 pages, 6 figures, 3 tables; accepted by MNRAS Letters; full
electronic versions of 2 tables are available from the preprint source; text
and tables are updated, a figure adde
Paradoxes of the Aharonov-Bohm and the Aharonov-Casher effects
For a believer in locality of Nature, the Aharonov-Bohm effect and the
Aharonov-Casher effect are paradoxes. I discuss these and other Aharonov's
paradoxes and propose a local explanation of these effects. If the solenoid in
the Aharonov-Bohm effect is treated quantum mechanically, the effect can be
explained via local interaction between the field of the electron and the
solenoid. I argue that the core of the Aharonov-Bohm and the Aharonov-Casher
effects is that of quantum entanglement: the quantum wave function describes
all systems together.Comment: To be published in Yakir Aharonov 80th birthday Festschrif
Lifetime Difference and Endpoint effect in the Inclusive Bottom Hadron Decays
The lifetime differences of bottom hadrons are known to be properly explained
within the framework of heavy quark effective field theory(HQEFT) of QCD via
the inverse expansion of the dressed heavy quark mass. In general, the spectrum
around the endpoint region is not well behaved due to the invalidity of
expansion near the endpoint. The curve fitting method is adopted to treat the
endpoint behavior. It turns out that the endpoint effects are truly small and
the explanation on the lifetime differences in the HQEFT of QCD is then well
justified. The inclusion of the endpoint effects makes the prediction on the
lifetime differences and the extraction on the CKM matrix element
more reliable.Comment: 11 pages, Revtex, 10 figures, 6 tables, published versio
Lepton flavor-changing Scalar Interactions and Muon
A systematic investigation on muon anomalous magnetic moment and related
lepton flavor-violating process such as \m\to e\g, \t\to e\g and \t\to
\m\g is made at two loop level in the models with flavor-changing scalar
interactions. The two loop diagrams with double scalar exchanges are studied
and their contributions are found to be compatible with the ones from Barr-Zee
diagram. By comparing with the latest data, the allowed ranges for the relevant
Yukawa couplings in lepton sector are obtained. The results show a
hierarchical structure of Y_{\m e, \t e} \ll Y_{\m \t} \simeq Y_{\m\m} in the
physical basis if is found to be . It
deviates from the widely used ansatz in which the off diagonal elements are
proportional to the square root of the products of related fermion masses. An
alternative Yukawa coupling matrix in the lepton sector is suggested to
understand the current data. With such a reasonable Yukawa coupling ansatz, the
decay rate of \t\to \m\g is found to be near the current experiment upper
bound.Comment: 15 pages, Revtex, 9 figures, published version in EPJ
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