10,590 research outputs found
Determining the luminosity function of Swift long gamma-ray bursts with pseudo-redshifts
The determination of luminosity function (LF) of gamma-ray bursts (GRBs) is
of an important role for the cosmological applications of the GRBs, which is
however hindered seriously by some selection effects due to redshift
measurements. In order to avoid these selection effects, we suggest to
calculate pseudo-redshifts for Swift GRBs according to the empirical L-E_p
relationship. Here, such a relationship is determined by reconciling
the distributions of pseudo- and real redshifts of redshift-known GRBs. The
values of E_p taken from Butler's GRB catalog are estimated with Bayesian
statistics rather than observed. Using the GRB sample with pseudo-redshifts of
a relatively large number, we fit the redshift-resolved luminosity
distributions of the GRBs with a broken-power-law LF. The fitting results
suggest that the LF could evolve with redshift by a redshift-dependent break
luminosity, e.g., L_b=1.2\times10^{51}(1+z)^2\rm erg s^{-1}. The low- and
high-luminosity indices are constrained to 0.8 and 2.0, respectively. It is
found that the proportional coefficient between GRB event rate and star
formation rate should correspondingly decrease with increasing redshifts.Comment: 5 pages, 5 figures, accepted for publication in ApJ
A novel hybrid protocol for semiquantum key distribution and semiquantum secret sharing
In this paper, a novel hybrid protocol for semiquantum key distribution
(SQKD) and semiquantum secret sharing (SQSS) was constructed by using GHZ-like
states. This protocol is capable of establishing two different private keys
between one quantum party and two semiquantum parties respectively, and making
two semiquantum parties share another private key of the quantum party in the
meanwhile. The usages of delay lines, Pauli operations, Hadamard gates and
quantum entanglement swapping are not required. Moreover, the semiquantum
parties are not necessary to be equipped with any quantum memory. We validate
in detail that this protocol resists various attacks from Eve, including the
Trojan horse attacks, the entangle-measure attack, the double controlled-not
(CNOT) attacks, the measure-resend attack and the intercept-resend attack. To
our best knowledge, this protocol is the only protocol which possesses the
functions of both SQKD and SQSS simultaneously until now.Comment: 16 pages,1 figure, 3 table
Continuous-time control synthesis under nested signal temporal logic specifications
Signal temporal logic (STL) has gained popularity in robotics for expressing
complex specifications that may involve timing requirements or deadlines. While
the control synthesis for STL specifications without nested temporal operators
has been studied in the literature, the case of nested temporal operators is
substantially more challenging and requires new theoretical advancements. In
this work, we propose an efficient continuous-time control synthesis framework
for nonlinear systems under nested STL specifications. The framework is based
on the notions of signal temporal logic tree (sTLT) and control barrier
function (CBF). In particular, we detail the construction of an sTLT from a
given STL formula and a continuous-time dynamical system, the sTLT semantics
(i.e., satisfaction condition), and the equivalence or under-approximation
relation between sTLT and STL. Leveraging the fact that the satisfaction
condition of an sTLT is essentially keeping the state within certain sets
during certain time intervals, it provides explicit guidelines for the CBF
design. The resulting controller is obtained through the utilization of an
online CBF-based program coupled with an event-triggered scheme for online
updating the activation time interval of each CBF, with which the correctness
of the system behavior can be established by construction. We demonstrate the
efficacy of the proposed method for single-integrator and unicycle models under
nested STL formulas.Comment: Link to accompanying code: https://github.com/xiaotanKTH/sTL
Choroid thickness in central serous chorioretinopathy using enhanced depth imaging optical coherence tomography
AIM: To observe the choroidal thickness in the macular area in affected and unaffected fellow eyes with central serous chorio retinopathy(CSC)and in healthy controls. METHODS: Twenty-six cases with unilateral CSC and controls were recruited in this study. All eyes were divided into three groups: 26 eyes in Group A(affected eyes with CSC), 26 eyes in group B(unaffected fellow eyes)and 26 eyes in group C(right eyes of age and sex matched control). Enhanced depth imaging was obtained by using spectral-domain optical coherence tomography. Subfoveal choroidal thickness and choroidal thickness at 1mm/3mm nasal, temporal, superior and inferior to the fovea were measured. RESULTS: Choroidal thickness was significantly increased in affected eyes with CSC than unaffected fellow eyes(t=5.57, P<0.01).The mean subfoveal choroidal thickness(SFCT)was 528.31±91.24μm in group A, 413.71±79.35μm in group B, and 301.31±52.46 in group C. The subfoveal choroid was significantly thicker in group A than Group C(P<0.01). SFCT in unaffected fellow eyes were thicker than the controls(P<0.01). CONCLUSION:Choroidal thickness is thicker in affected eyes with CSC and also in fellow unaffected eyes, indicating that the choroid blood vessels are high and perfusion state, may be one of the factors of the disease CSC
Gravito-Electromagnetic coupled perturbations and quasinormal modes of a charged black hole with scalar hair
From the quantum point of view, singularity should not exist. Recently, Bah
and Heidmann constructed a five-dimensional singularity free topology
star/black hole [Phys. Rev. Lett. 126, 151101 (2021)]. By integrating the extra
dimension, a four-dimensional static spherical black hole with a magnetic
charge and scalar hair can be obtained. In this paper, we study the quasinormal
modes (QNMs) of the magnetic field and gravitational field on the background of
this four-dimensional charged black hole with scalar hair. The odd parity of
the gravitational perturbations couples with the even parity of the magnetic
field perturbations. Two coupled second-order derivative equations are
obtained. Using the matrix-valued direct integration method, we obtain the
fundamental QNM frequencies numerically. The effect of the magnetic charge on
the QNMs is studied. The differences of the frequencies of the fundamental QNMs
between the charged black hole with scalar hair and the Reissner-Norstr\"{o}m
black hole are very small for the angular number . However, some new
interesting results are found for higher angular number.Comment: 10 pages, 3 figures, 2 tables, some mistakes have been correcte
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