Unit:
Τομέας Αστροφυσικής, Αστρονομίας και ΜηχανικήςLibrary of the School of Science
Dissertation committee:
Θεοχάρης Αποστολάτος (επιβλέπων) Επικ. Καθηγητής Τμήμ. Φυσικής ΕΚΠΑ, Θεοδόσης Χριστοδουλάκης Αναπλ. Καθηγητής Τμήμ. Φυσικής ΕΚΠΑ, Μιχάλης Τσαμπαρλής Αναπλ. Καθηγητής Τμήμ. Φυσικής ΕΚΠΑ
Original Title:
Εφαρμογές στη γενική θεωρία της σχετικότητας: ο χώρος γύρω από συμπαγή αστροφυσικά αντικείμενα
Summary:
The study of the astrophysical phenomena that take place near compact objects
(CO) offers an unprecedented opportunity to explore the boundaries of known
physics, i.e. test general relativity in strong gravity regions and map their
internal structure.
To perform these tasks one needs an accurate description for the spacetime.
This motivated the current work on the possibility of describing accurately the
exterior of neutron stars (NS) by using analytic spacetimes. We first developed
all the tools needed to compare realistic (numerical) NS spacetimes to analytic
spacetimes, that is, we identified correctly the relativistic multipole moments
of numerical spacetimes and developed an algorithm to transform the coordinates
from those of the numerical spacetime to those of the analytic spacetime.
We then proceeded to compare realistic NS spacetimes to analytic ones which
were constructed to have the same multipole moments as the numerical ones. The
comparison between the corresponding metrics was based on geometrical and
physical properties associated to astrophysical phenomena. We have shown that
the so called Two-Soliton metric is a very good approximation of the spacetime
exterior to NSs of arbitrary rotation.
Using the Two-Soliton we have investigated the properties of COs through the
behaviour of quasi-periodic oscillations (QPOs). From this investigation, we
have identified properties that these oscillations might display, that could be
used, (i) to demonstrate that these QPOs are orbital in nature, (ii) to
distinguish NSs with different equations of state.
Keywords:
General relativity, Exact solutions, Neutron stars, Multipole moments, X-ray binaries
Number of index pages:
VIII - XXI
Number of pages:
XXIV, 181
