The swimming of a pair of spherical bladders that change their volumes and mutual distance is efficient at low Reynolds numbers and is superior to other models of artificial swimmers. The change of shape resembles the wriggling motion known as metaboly of certain protozoa.

We propose a novel scenario to explain the observed cosmological asymmetry between matter and antimatter, based on nonperturbative QCD physics. This scenario relies on a mechanism of separation of quarks and antiquarks in two coexisting phases at the end of the cosmological QCD phase transition: ordinary hadrons (and antihadrons), along with massive lumps (and antilumps) of novel color superconducting phase. The latter would serve as the cosmological cold dark matter. In certain conditions the separation of charge is C and CP asymmetric and can leave a net excess of hadrons over antihadrons in the conventional phase, even if the visible universe is globally baryon symmetric B = 0. In this case an equal, but negative, overall baryon charge must be hidden in the lumps of novel phase. Due to the small volume occupied by these dense lumps/antilumps of color superconducting phase and the specific features of their interaction with "normal" matter in hadronic phase, this scenario does not contradict the current phenomenological constrains on presence of antimatter in the visible universe. Moreover, in this scenario the observed cosmological ratio ΩDM ∼ ΩB within an order of magnitude finds a natural explanation, as both contributions to Ω originated from the same physics during the QCD phase transition. The baryon to entropy ratio nB/nγ ∼ 10 −10 would also be a natural outcome, fixed by the temperature T f < ∼ TQCD at which the separation of phases is completed.PACS numbers: 98.80. Cq, 95.30.Cq, 95.35.+d,

We discuss the possibility that the recent detection of 511 keV γ rays from the galactic bulge, as observed by INTEGRAL, can be naturally explained by the supermassive very dense droplets (strangelets) of dark matter. These droplets are assumed to be made of ordinary light quarks (or antiquarks) condensed in non-hadronic color superconducting phase. The droplets can carry electrons (or positrons) in the bulk or/and on the surface. The e + e − annihilation events take place due to the collisions of electrons from the visible matter with positrons from dark matter droplets which may result in the bright 511 KeV γ-ray line from the bulge of the Galaxy.PACS numbers: 98.80. Cq, 95.30.Cq, 95.35.+d,

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It is suggested that the Minkowski vacuum of quantum field theories of a large number of fields N would be gravitationally unstable due to strong vacuum energy fluctuations unless an N dependent sub-Planckian ultraviolet momentum cutoff is introduced. We estimate this implied cutoff using an effective quantum theory of massless fields that couple to semiclassical gravity and find it ͑assuming that the cosmological constant vanishes͒ to be bounded by M Planck /N 1/4 . Our bound can be made consistent with entropy bounds and holography, but does not seem to be equivalent to either, and it relaxes but does not eliminate the implied bound on N inherent in entropy bounds.