QUANTIZING TORSION EFFECTS IN A DE SITTER UNIVERSE
IOANNIS IRAKLIS HARANAS 1, MICHAEL HARNEY 2
1 Department
of Physics and Astronomy,
314 A
E-mail:
ioannis@yorku.ca
2 841
North 700 West, Pleasant
E-mail:
michael.harney@signaldisplay.com
Abstract. We derive
quantization relations in the case when torsion effects
are added in a De Sitter spacetime metric
with or without a black hole at the Planck
mass and Planck length limit. To this end we use Zeldovich’s definition
of the
cosmological constant.
Key words: gravitation
– quantization
– torsion – spin – black holes.
WAVE PROPERTIES OF COLD PLASMA AROUND THE EVENT HORIZON OF A DE SITTER BLACK HOLE
MOHAMMAD KHAYRUL HASAN 1, MOHAMMAD HOSSAIN ALI 2
1 Department of Mathematics
Sylhet-3100,
E-mail:
khayrulmat@gmail.com
2 Department of Applied Mathematics
Rajshahi-6205,
E-mail:
m_hossain_ali_bd@yahoo.com
DETERMINATION OF THE HUBBLE CONSTANT USING CEPHEIDS
MOHAMED ABDEL-SABOUR
1, MOHAMED
EBRAHIM NOUH 1, ISSA
ALI ISSA 1,
MOHAMED SALEH EL-NAWAWY 2,3, AYMAN KORDI 3, ZAKI ALMOSTAFA 3,4,
AHMAD ESSAM EL-SAID 1, GAMAL BAKR ALi 1,
1 National Research Institute of Astronomy and Geophysics (NRIAG)
11421-Helwan,
Cairo, Egypt
E-mails:
msabour@nriag.sci.eg, sabour2000@hotmail.com,
abdo_nouh@hotmail.com,
essam60@yahoo.com,
gamalali@lycos.com
2 Astronomy
Department, Faculty of Science,
Cairo,
Egypt
E-mail:
msnawawy@yahoo.com
3 Physics
and Astronomy Department, Faculty of Science,
Riyadh,
Saudi Arabia
E-mail:
aymankurdi@yahoo.com
4 King
Abdelaziz City for Science Technology
Riyadh,
Saudi Arabia
E-mail:
zalmostafa@kacst.edu.sa
Abstract. This
paper introduces a statistical treatment to use Cepheid variable stars
as
distance indicators. The expansion rate
of the Universe is also studied here through
deriving the value of the Hubble constant H0.
A Gaussian function approximation is
proposed to fit the absolute magnitude and
period of Cepheid variables in our galaxy. The calculations are carried
out on
samples
of Cepheids observed in 23 galaxies to derive the distance modulus (DM)
of these galaxies based on the frequency distributions
of their periods and
intrinsic apparent magnitudes.
The
DM is the difference between the apparent magnitude for extragalactic
Cepheids
and the absolute magnitude of the galactic
Cepheids at maximum number. It is
calculated by using the comparison of the period distribution of
Cepheids in our
galaxy and in
other galaxies.
This
method is preferred due to its
simplicity to use and its efficiency
in providing reliable DM. A linear fit with correlation
coefficient of
99.68% has been found between the published distance modulus and
that
computed one in the present work. From
the present sample, a value of H0 in the
range of 66 to 80 ±
5 km s–1 Mpc–1 is determined.
The
present procedure of computation and its accuracy are confirmed by the
high
correlation found between our computed
DM and that published in the literature.
Key
words: variable stars – Cepheids – Hubble
constant.
NEUTRON STAR MODELS WITH DOUCHIN-HAENSEL-PICHON EQUATIONS OF STATE
Vasile
Ureche 1, Rodica Roman 2, ovidiu
furdui 2
1 “Babeş-Bolyai” University, Faculty of Mathematics and Computer Science
Str.
M.
Kogălniceanu 1, 400084 Cluj-Napoca, Romania
E-mail:
vureche@math.ubbcluj.ro
2 Astronomical
Institute of the
Astronomical
Observatory Cluj-Napoca
Str.
Cireşilor
19, 400487 Cluj-Napoca, Romania
E-mail:
rdcroman@yahoo.com,
ovidiu.furdui@gmail.com
Abstract. In a previous
paper (Ureche et al. 2007) we computed neutron star
models by using the equation of state (EOS) obtained
by Douchin and Haensel
(2001). Now we extend the results combining the quoted EOS (for core
and inner
crust) with the EOS given
by Haensel and Pichon (1994) (for outer crust). The
results are given in graphical form, in which the variations of mass
and radius
are
given as functions of central density and of dimensionless central
pressure. The last one is a measure of the compactness of the star,
that is,
a
measure of the strength of gravitational field. The numerical results
confirm
our previous results and are in good agreement with those
obtained by Douchin
and Haensel. The maximum mass, reached at the central density
2.098×1018
kg m–3 is 2.17 solar masses, and the
corresponding radius is 11.58
km. Combining the EOS of Douchin and Haensel with the EOS of Haensel
and Pichon
we succeed in
determining the minimum mass of neutron stars. This is 0.079
solar masses (reached at central density 2.31×1017 kg m–3),
whereas the
corresponding radius is 19.02 km. We also study the space-time
geometry inside the neutron star and in its neighborhood, and we
determine the
coefficients that give the proper time and the radial distance.
Key words: stellar structure – neutron stars – space-time geometry.
DATA MINING IN SATELLITE IMAGES USING THE PRDC TECHNIQUE
CǍTǍLIN CUCU-DUMITRESCU
1,3,
MIHAI
DATCU 2,
MANUEL
BUICAN 3
1 Astronomical
Institute of the
Str.
Cuţitul de
Argint 5, 040557 Bucharest, Romania
E-mail:
cucudumitrescu@yahoo.com
2 Remote Sensing Technology Institute IMF, German Aerospace Center DLR
Oberpfaffenhofen,
D-82234, Wessling,Germany
E-mail:
mihai.datcu@dlr.de
3 Advanced
Studies and
Str.
Jules Michelet 1, 010461
E-mail:
florin.serban@asrc.ro, mbuican@yahoo.com
Abstract. We
present some theoretical extensions of the PRDC technique (Pattern
Representation Scheme using Data Compression)
and a series of examples for the
use to satellite image segmentation and classification. The technical
and
mathematical principles used are
described and a new way of measuring the
compression ratio is introduced for comparing different areas of an
image.
Also, we present a
simple but efficient algorithm for eliminating the small
objects through absorption into the larger ones.
Key
words: remote sensing – data
mining – satellite image segmentation – PRDC technique – PCA technique
–
automatic recognition
and classification.
ARCHITECTURAL EVOLUTION OF ASTRONOMICAL OBSERVATORIES
Cristiana Dumitrache 1, Daniel
Dumitrache 2
1 Astronomical
Institute
of the
Str.
Cuţitul de Argint 5, 040557 Bucharest, Romania
E-mail:
crisd@aira.astro.ro
2 Spiru Haret University, Faculty of Architecture
Str.
Ion Ghica 13,
Abstract. We review the
development of an astronomical observatory mainly from the
architectural
standpoint and less via astronomical
knowledge or instruments evolution. Our
approach is an attempt to summarize the evolution of the buildings from
the
stage of instruments
to the complex modern stage with many functions and even
with their cultural role.
Key words: history of astronomy – observatories – architecture.