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- Tartu ObservatoryEE251 papers
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- Estonian Academy of SciencesEE50 papers
- University of HelsinkiFI48 papers
- Johannes Gutenberg University MainzDE41 papers
- Leibniz Institute for Astrophysics PotsdamDE40 papers
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6 papers · 1 filter
One-loop approximation for the Heisenberg antiferromagnet
A. Sherman, M. Schreiber
We use the diagram technique for spin operators to calculate Green's functions and observables of the spin-1/2 quantum Heisenberg antiferromagnet on a square lattice. The first cor…
The eclipsing binary millisecond pulsar PSR B1744-24A - possible test for a magnetic braking mechanism
Ene Ergma, Marek J. Sarna
As presented by Nice et al. (2000), long-term timing of the eclipsing binary PSR B1744-24A shows that the orbital period of this system decreases with a time-scale of only ~ 200 My…
An evolutionary scenario for the U Scorpii
Ene Ergma, Jelena Gerskevits, Marek J. Sarna
We perform evolutionary calculations of binary stars to find progenitors of systems with parameters similar to the recurrent novae U Sco. We show that a U Sco type-system may be fo…
Helium white dwarf in PSR J0751+1807; too cool, in PSR J1012+5307; too hot?
Ene Ergma, Marek J. Sarna, Jelena Gerskevits-Antipova
We discuss the cooling history of the low-mass, helium core white dwarfs in short orbital period millisecond pulsars PSR J0751+1807 and PSR J1012+5307. The revised cooling age esti…
Cooling curves and initial models for low-mass white dwarfs (<0.25 Msun) with helium core
Marek J. Sarna, Ene Ergma, Jelena Antipova
We present a detailed calculation of the evolution of low-mass () helium white dwarfs. These white dwarfs (the optical companions to binary millisecond pulsars) ar…
Algebra of differential forms with exterior differential in dimension one
V. Abramov, N. Bazunova
In this work, we construct the algebra of differential forms with the cube of exterior differential equal to zero on one-dimensional space. We prove that this algebra is a graded q…