Research topics - different intensities at Licencjat/Magister/Doktorat level
Non-perturbative N-body simulations
mag/lic, astronomia/fizyka matematyczna
N-body simulations (e.g.
AstroPh:0411043,
ArXiv:1105.1082,
AstroPh:0111367) used for the modelling of 0.1 to 5 Gpc scale structure formation assume a rigid Friedmann-Lemaitre-Robertson-Walker (FLRW) background against which perturbations grow according to Newtonian gravity, while the FLRW background itself evolves assuming that structure formation do
not form. An UMK-Lyon project is underway to develop relativistic methods of correcting N-body simulations for this contradiction, by using scalar averaging (
AstroPh:9912347,
ArXiv:0707.2153,
ArXiv:0803.1401,
ArXiv:1203.6263,
ArXiv:1303.6193). A possible long-term result of the full project would be that the more accurate simulations would help show that "dark energy" is a misinterpretation of the virialisation epoch, during which much of the most massive galaxies and galaxy clusters formed. A student working on this project would work together with other team members in UMK and Lyon.
http://cosmo.torun.pl/Cosmo/LicMagTematy
Measuring metric inhomogeneity with BAO
mag/lic, astronomia/fizyka matematyczna
The Universe is not homogeneous, but the Concordance Model starts with a spatially-homogeneous solution to the Einstein field equations and afterwards applies perturbations. The scalar averaging approach (
AstroPh:9912347,
ArXiv:0707.2153,
ArXiv:0803.1401,
ArXiv:1203.6263,
ArXiv:1303.6193) proposes a relativistically more realistic approach to cosmological modelling. The initial measurement of a shift of about 6% in the baryonic acoustic oscillation (BAO) peak location (
ArXiv:1410.1687) in overdense regions provides the first tentative evidence of metric inhomogeneity. The calculations using the presently available software are cpu-intensive. A student would help develop algorithmic speedups, tests of the different software modules, and possibly GPGPU modules under
OpenCL.
http://cosmo.torun.pl/Cosmo/LicMagTematy
już ktoś robi...
źródło: LambdaStudentTematAbstrakt
Czy ,,stała kosmologiczna" jest tylko efekt uśrednienia niejednorodności?
Is the cosmological constant just the result of inhomogeneities?
See e.g. Buchert et al.
GrQc:0210037,
GrQc:0210045,
AstroPh:9609036
Stary
"Stary" does not necessarily mean the topic is no longer open. It only means that I (Boud) do not see it as a good student topic that I am interested in supervising right now.
The averaging problem
(todo: rewrite) How significant are the errors introduced by the FLRW approximation? See e.g. Buchert et al
ArXiv:0803.1401,
ArXiv:1103.2016; Wiltshire
ArXiv:0912.5234; Krasinski et al
ArXiv:0903.4070,
ArXiv:1102.1449. Check at least one of these calculations at the level appropriate for your level of studies.
Topology of the Universe Detection
- In http://de.arxiv.org/abs/0801.0006, it seems that we may have measured the shape of the Universe, since certain parts of the cosmic microwave background seen by the WMAP satellite appear to be seen twice in different directions on the sky, due to topological lensing. The purpose of the masters/licencjat project is:
- Aim: Propose and apply a further test using WMAP data which further tests the hypothesis. This requires:
- Reading/writing/managing the WMAP data file with free software computer programs
- Statistical analysis
- Independently checking that the computer code does the algebraic and statistical analyses correctly
źródło: LDMStudentTematAbstrakt
Dark Matter - Light Dark Matter (LDM) hypothesis - Galaxy Centre INTEGRAL results
CMB/WMAP/Planck - the Missing Fluctuations problem
mag/lic, astronomia/fizyka matematyczna
WMAP data are
too homogeneous on the largest scales to match the infinite flat model, e.g. see Copi et al. 2009
ArXiv:0808.3767,
ArXiv:1201.2459,
ArXiv:1103.3505. Summarise the evidence; discuss the correlation function versus spherical harmonic interpretations of the data; list possible explanations, including the topology of the Universe as discussed by Karl Schwarzschild, Leopold Infeld, et al.
http://cosmo.torun.pl/Cosmo/LicMagTematy
Topology of the Universe
mag/lic, astronomia/fizyka matematyczna
If you are interested in cosmic topology and have good software skills and/or a good understanding of differential geometry, many interesting observational and theoretical projects are available upon consultation - start reading at
MonographCosmo.
http://cosmo.torun.pl/Cosmo/LicMagTematy
Clusters, Lambda, and OCRA/SZ Effect
mag/lic, astronomia/fizyka matematyczna
The largest gravitationally collapsed (virialised) objects in the Universe are clusters of galaxies. In principle, these should be easy to use as cosmological tracer objects in various ways. The simplest interpretation of clusters observed by XMM-Newton using the apparent gas fraction at the virial radius appeared to support a high-density (e.g. zero cosmological constant) model - Sadat et al. 2005
AstroPh:0503426, in contradiction to the Concordance Model. Resolving this contradiction may lead to new understanding of the dynamics and outer parts of clusters, e.g. Kay et al. 2007
AstroPh:0611017, Ferramacho, Blanchard 2007
AstroPh:0609822. Estimate what role RT4/OCRA-f and RTK could play in testing our understanding of clusters.
http://cosmo.torun.pl/Cosmo/LicMagTematy
Dark Matter (DM)
mag/lic, astronomia/fizyka matematyczna
Summarise the evidence; list different types of explanations; give arguments for and against the different candidates; investigate the evidence numerically and produce your own plots. In particular,
- the Light Dark Matter hypothesis AstroPh:0507142 seems very interesting (is the 511 keV line emission in the galactic centre due to annihilating LDM?); and
- the DAMA/NaI and DAMA/LIBRA results are interesting - see Bernabei et al. (2008), ArXiv:0804.2741 "the presence of Dark Matter particles in the galactic halo is supported, on the basis of the DM annual modulation signature, at 8.2 σ C.L." and Savage et al. (2009), ArXiv:0808.3607 and references therein;
- the CDMS (Cryogenic Dark Matter Search) initial results look exciting.
- could DM be an artefact induced by not applying general relativity correctly? see Buchert & Wiegand ArXiv:1002.3912
- Warning: microlensing (OGLE etc.) so far only gives evidence of that DM is (mostly) not composed of stellar-mass MACHOs e.g. AstroPh:0607207.
http://cosmo.torun.pl/Cosmo/LicMagTematy
Cosmic String Detection
- In http://de.arxiv.org/abs/astro-ph/0410073 Kibble discusses the
http://de.arxiv.org/abs/astro-ph/302547 possible detection of a cosmic string which seems to gravitationally lens a background galaxy (Sazhin et al.) In http://de.arxiv.org/abs/astro-ph/0406516 the extra pairs of lensed galaxies predicted by the hypothesis are discussed. - see AstroPh:0601494 Sazhin et al.
- Aim: Understand the basics about (1) cosmic strings, (2) gravitational lensing versus cosmic string lensing, and test the hypothesis
- Calculate the probability of seeing the original pair by chance
- Check whether the statistics of expected numbers of lensed images are correct
- Propose an independent test of the hypothesis, e.g. using radio observations and prepare an observing proposal
- compare with conventional gravitational lensing interpretations
źródło: DAMAStudentTematAbstrakt
Dark Matter Detection - DAMA/NaI + Foot et al.
- In http://de.arxiv.org/abs/astro-ph/0405282 the 7 year results of the DAMA/NaI dark matter direct detection experiment show a signal significant at 6.3σ according to the authors. An explanation for why a signal from mirror-baryonic matter should be expected in this experiment but not in others with similar cross-section detection parameters is presented in AstroPh:0403043, see also AstroPh:0407623 and references therein.
- Aim: Check the experimental and theoretical claims and propose further tests
- Try to find an alternative explanation for the DAMA/NaI results without going beyond the Standard Model of particle physics
- Check whether the Foot et al. calculations of mirror matter properties are consistent with all the experimental data as the authors claim
- Extend the Foot et al. calculations to find, e.g. a non-gravitational effect of mirror matter in stellar physics, e.g. symbiotic stars (gravitational effects of dark matter are already well studied)
- More info: http://adjani.astro.uni.torun.pl/cgi-bin/twiki/view/Cosmo/NonBaryonicDarkMatter#the_DAMA_NaI_detection_and_mirro