16,466 research outputs found
Superconducting cosmic strings as sources of cosmological fast radio bursts
In this paper we calculate the radio burst signals from three kinds of
structures of superconducting cosmic strings. By taking into account the
observational factors including scattering and relativistic effects, we derive
the event rate of radio bursts as a function of redshift with the theoretical
parameters and of superconducting strings. Our analyses
show that cusps and kinks may have noticeable contributions to the event rate
and in most cases cusps would dominate the contribution, while the kink-kink
collisions tend to have secondary effects. By fitting theoretical predictions
with the normalized data of fast radio bursts, we for the first time constrain
the parameter space of superconducting strings and report that the parameter
space of and fit the observation well although the statistic
significance is low due to the lack of observational data. Moreover, we derive
two types of best fittings, with one being dominated by cusps with a redshift
, and the other dominated by kinks at the range of the maximal event
rate.Comment: 13 pages, 2 figures, 1 table; references update
Weak Decays of Stable Open-bottom Tetraquark by SU(3) Symmetry Analysis
The exotic state which was observed by D0 Collaboration is very
likely to be a tetraquark state with four different valence quark flavors,
though the existence was not confirmed by other collaborations. The possibility
of such state still generate lots of interests in theory. In the paper, we will
study the properties of the state under the SU(3) flavor symmetry. This four
quark state with a heavy bottom quark and three light quarks(anti-quark) can
form a or representation. The weak decays can be dominant
and should be discussed carefully while such state is stable against the strong
interaction. Therefor we will study the multi-body semileptonic and nonleptonic
weak decays systematically. With the help of SU(3) flavor symmetry, we can give
the Hamiltonian in the hadronic level, then obtain the parameterized
irreducible amplitudes and the relations of different channels. At the end of
the article, we collect some Cabibbo allowed two-body and three-body weak decay
channels which can be used to reconstruct states at the branching
fraction up to be .Comment: 53 pages, 2 figure
A New Class of Attacks on Time Series Data Mining
Traditional research on preserving privacy in data mining focuses on time-invariant privacy issues. With the emergence of time series data mining, traditional snapshot-based privacy issues need to be extended to be multi-dimensional with the addition of time dimension. We find current techniques to preserve privacy in data mining are not effective in preserving time-domain privacy. We present the data flow separation attack on privacy in time series data mining, which is based on blind source separation techniques from statistical signal processing. Our experiments with real data show that this attack is effective. By combining the data flow separation method and the frequency matching method, an attacker can identify data sources and compromise time-domain privacy. We propose possible countermeasures to the data flow separation attack in the paper
A New Class of Attacks on Time Series Data Mining
Traditional research on preserving privacy in data mining focuses on time-invariant privacy issues. With the emergence of time series data mining, traditional snapshot-based privacy issues need to be extended to be multi-dimensional with the addition of time dimension. We find current techniques to preserve privacy in data mining are not effective in preserving time-domain privacy. We present the data flow separation attack on privacy in time series data mining, which is based on blind source separation techniques from statistical signal processing. Our experiments with real data show that this attack is effective. By combining the data flow separation method and the frequency matching method, an attacker can identify data sources and compromise time-domain privacy. We propose possible countermeasures to the data flow separation attack in the paper
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