QUANTIZING  TORSION  EFFECTS  IN  A  DE  SITTER  UNIVERSE

IOANNIS  IRAKLIS  HARANAS 1,  MICHAEL  HARNEY 2

1 Department of Physics and Astronomy, York University

314 A Petrie Building, 4700 Keele Avenue, Toronto, Ontario, M3J-1P3, Canada

E-mail: ioannis@yorku.ca

 

2 841 North 700 West, Pleasant Crove, Utah, 84062, USA

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

 Shahjalal University of Science and Technology

Sylhet-3100, Bangladesh

E-mail: khayrulmat@gmail.com

 

2 Department of Applied Mathematics

University of Rajshahi

Rajshahi-6205, Bangladesh

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 University

Cairo, Egypt

E-mail: msnawawy@yahoo.com

 

3 Physics and Astronomy Department, Faculty of Science, King Saud University

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 Romanian Academy

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,  FLORIN  ŞERBAN 3,

MANUEL  BUICAN 3

1 Astronomical Institute of the Romanian Academy

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 Research Center

Str. Jules Michelet 1, 010461 Bucharest, Romania

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 Romanian Academy

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, Bucharest, Romania

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.