# Doktorat na TCfA

## administrative steps

## conditions

- stipends:
- normal stipends are only for Polish citizens (EU rules should, in principle, allow other EU citizens, but this may not yet be implemented in national law nor in UMK rules)
- stipend only lasts for one year; new competition for stipends each year of doctorate, depending on chance and a supposedly meritocratic points system
- grants can be applied for in the national grant system (NCN), partly written in English, partly written in Polish

- in addition to research, the doctorant must:
- study several courses and take exams
- possibly do extra courses with exams if s/he did not study astronomy directly (e.g. physics/maths graduate)
- carry out many hours of unpaid teaching/tutoring

- the "przewod doktorski" (declaration of intent to submit a thesis) must be "opened" by the second year at latest

## visits by scientists from Central/Eastern Europe

- Mianowski Fund: 1-12 months research visit, if you already have a position and a degree (master's maybe enough?) in your home country
- mianowski waw pl/programme.htm

## Ewentualny Tematy

#### Non-perturbative N-body/GR simulations

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). The main result of the full project (

ArXiv:1706.06179) is that more accurate simulations help show that "dark energy" is a misinterpretation of the virialisation epoch, during which much of the most massive galaxies and galaxy clusters formed. The student's contribution would be in checking caveats of this calculational method and/or proposing extensions.

http://cosmo.torun.pl/Cosmo/DoktoratTematy
#### Measuring metric inhomogeneity with BAO

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/DoktoratTematy