Stanislaw Bajtlik

• Nicolaus Copernicus Astronomical Center

We discuss a rather surprising version of the twin paradox in which (contrary to the familiar classical version) the twin who accelerates is older on the reunion than his never accelerating brother.

Recently [arXiv:astro-ph/0612155] we presented a formal mathematical proof that, contrary to a widespread misconception, cosmological expansion cannot be understood as the motion of galaxies in non-expanding space. We showed that the cosmological redshift must be physically interpreted as the expansion of space. Although our proof was generally acc...

Recently we presented a formal mathematical proof that, contrary to a widespread misconception, cosmological expansion cannot be understood as the motion of galaxies in non-expanding space. We showed that the cosmological redshift must be physically interpreted as the expansion of space. Although our proof was generally accepted, a few authors disa...

The rather wide-spread belief that cosmological expansion of a flat 3D--space (with spatial curvature k=0) cannot be observationally distinguished from a kinematics of galaxies moving in a flat and non-expanding space is erroneous. We suggest that the error may have its source in a non relativistic intuition that imagines the Universe not as a spac...

The rather wide-spread belief that cosmological expansion of a flat 3D-space (with spatial curvature k = 0) cannot be observationally distinguished from a kinematics of galaxies moving in a flat and non-expanding space is erroneous. We suggest that the error may have its source in a non relativistic intuition that imagines the Universe not as a spa...

We consider a new version of the twin paradox. The twins move along the same circular free photon path around the Schwarzschild center. In this case, despite their different velocities, all twins have the same non-zero acceleration. On the circular photon path, the symmetry between the twins situations is broken not by acceleration (as it is in the...

In a multiply connected space, the two twins of the special relativity twin paradox move with constant relative speed and meet a second time without acceleration. The twins' situations appear to be symmetrical despite the need for one to be younger due to time dilation. Here, the suggestion that the apparent symmetry is broken by homotopy classes o...

Could cosmic topology imply dark energy? We use a weak field (Newtonian) approximation of gravity and consider the gravitational effect from distant, multiple copies of a large, collapsed (virialised) object today (i.e. a massive galaxy cluster), taking into account the finite propagation speed of gravity, in a flat, multiply connected universe, an...

Cosmic crystallography is based on the principle that peaks in the pair separation histogram (PSH) of objects in a catalogue should be induced by the high number of topologically lensed pairs that are separated by Clifford translations, in excess to ``random'' pairs of objects. Here we present modifications of this method that successively improve...

Cosmic crystallography is based on the principle that peaks in the pair separation histogram (PSH) of objects in a catalogue should be induced by the high number of topologically lensed pairs that are separated by Clifford translations, in excess to ``random'' pairs of objects. Here we present modifications of this method that successively improve...

Luminet et al. (2003) suggested that WMAP data are better matched by a Poincar\'e dodecahedral FLRW model of global geometry, rather than by an infinite flat model. The analysis by Cornish et al. (2003) for angular radii 25-90 degrees failed to support this. Here, a matched circles analysis specifically designed to detect dodecahedral patterns of m...

In this brief essay we consider the concept of beginning in cosmology. It can be applied to the Universe as a whole, as well as to various epochs in the cosmic history and major structures as we can see them today.

Where's the matter? The answer seems to be: ``distributed according to a power spectrum with at least one feature (local maximum) near 120-130h^-1Mpc''. Analyses of the Iovino, Clowes & Shaver quasar candidate catalogue at z~2 and the 2dF Quasar Survey 10K Release (2QZ-10K) support this claim, which has previously been made both for low redshift su...

If the Universe satisfies a perturbed Friedmann-Lema\^{\i}tre model, then the bright matter (e.g. radio-loud active galactic nuclei, RLAGNs) may be topologically lensed by global geometry. The generation of candidate topological lensing pairs of RLAGNs, which may be double images of single objects seen at very different celestial positions, provide...

Detections of local maxima in the density perturbation spectrum at characteristic comoving scales L~100-200h^{-1}Mpc have previously been claimed. Here, this cosmic standard ruler is sought in the ``10K'' release of the 2dF QSO Redshift Survey (2QZ-10K), by estimating the comoving, spatial correlation functions \xi(r) of the three-dimensional distr...

The amplitude of the angular two-point galaxy autocorrelation function w(θ) for galaxies at z ̃ 2 is estimated for galaxies in the Hubble Deep Field by using a U<27 complete subsample. The U-band selection ensures little contamination from z>2.5 galaxies, while photometric redshifts minimize the contribution from low redshift galaxies. • It is con...

The study of the kinematics of galaxies within clusters or groups has the limitation that only one of the three velocity components and only two of the three spatial components of a galaxy position in six-dimensional phase-space can normally be measured. However, if multiple topological images of a cluster exist, then the radial positions and sky p...

The amplitude of the angular two-point galaxy correlation function w(\theta) for galaxies at z~2 is estimated for galaxies in the Hubble Deep Field by using a U < 27 complete sub-sample. (i) It is confirmed that the amplitude of the correlation can be corrected for the integral constraint without having to make assumptions about the shape of the co...

The basic observational facts known about the intergalactic medium in both smoothly distributed (IGM) and clumped forms (Lyα clouds) are reviewed. Six candidate theories of Lyα clouds and the IGM are compared with the essential non-controversial observational facts. Deficiencies of the theories and inconsistencies in the existing data sets are stre...

The general issue of using the Ly-alpha absorbers in quasar spectra as tracers of the large-scale matter distribution is discussed, emphasizing complications due to evolutionary effects and line blending. Then, a novel method of statistical analysis of the line data appropriate for studying large-scale structure is described. This method circumvent...

The distribution of lines in the Ly-alpha forests in quasar spectra is examined using spectral data from 19 quasars with emission lines redshifts z sub Q ranging from 1.7 to 3.8. The number density of Ly-alpha lines generally increases with resdhift z, but there exists a countervailing trend of diminishing number density within individual quasar sp...

In a statistical study of quasar absorption lines, no evidence is found for large voids in the Ly-alpha forest, contrary to some recent suggestions. The 28 Mpc gap found by Crotts (1987) in the spectrum of Q0420-388 is not statistically significant, and it is possible, from a sample of 18 quasar spectra, to reject at the 2 sigma level the hypothesi...

The temperature distribution of the microwave background radiation expected in flat and open cosmological models with shear is studied. In the flat (Bianchi type I) model, the anisotropy is quadrupole-like. In the open (type V) model, the anisotropy is focused into a small region of the sky: the 'hot spot'. The measurements of the temperature distr...

Primordial nucleosynthesis in a Bianchi type I universe is investigated. The effects, caused by the anisotropic momentum distribution of the electron neutrinos, neglected in earlier investigations, are taken into account. The authors show that the helium abundance is a rapidly decreasing function of the present value of the shear in the Hubble flow...

Context. Two of the biggest open questions in physical cosmology are the physical interpretation of the measured density of dark energy, and the still uncertain global shape of comoving space, especially including its topology. It was previously shown that multiple connectedness, via the twin paradox of special relativity, provides physical justifi...