We show that a bounded, isolated quantum system of many particles in specific initial state will approach thermal equilibrium if the energy eigenfunctions which are superposed to form obey Berry's conjecture. conjecture is expected hold only corresponding classical chaotic, and essentially states behave as they were Gaussian random variables. review existing evidence, previously neglected effects substantially strengthen case for study rarefied hard-sphere gas an explicit example many-body...

The ground-state density matrix for a massless free field is traced over the degrees of freedom residing inside an imaginary sphere; resulting entropy shown to be proportional area (and not volume) sphere. Possible connections with physics black holes are discussed.

If the Universe contains a nearly critical density of photinos which are also assumed to constitute dark matter in our galactic halo, then gravitational trapping by Sun and ensuing annihilation solar core yields significant flux \ensuremath{\sim}250-MeV neutrinos. This results about 2 neutrino-induced events per kiloton-year an underground proton-decay detector.

An isolated quantum many-body system in an initial pure state will come to thermal equilibrium if it satisfies the eigenstate thermalization hypothesis (ETH). We consider alternatives ETH that have been proposed. first show von Neumann's ergodic theorem relies on assumption is essentially equivalent ETH. also investigate whether, following a sudden quench, special classes of states can lead behavior systems do not obey ETH, namely, integrable systems. find examples this, but only for obeyed...

Observational tests of the hypothesis that universe is flat and dominated by dark matter in form massive photinos include production significant fluxes cosmic rays gamma our galactic halo. Specification cosmological photino density masses scalar quarks leptons determines present annihilation rate. The predicted number low-energy cosmic-ray antiprotons comparable to observed flux.

We consider many-body quantum systems that exhibit chaos, in the sense observables of interest act on energy eigenstates like banded random matrices. study time-dependent expectation values these observables, assuming system is a definite (but arbitrary) pure state. induce probability distribution for by treating zero time as uniformly distributed variable. show explicitly if an observable has non-equilibrium value at some particular moment, then it overwhelmingly likely to move towards...

We show that if our galactic halo were to consist of scalar or Dirac neutrinos with mass greater than \ensuremath{\sim}12 GeV, capture by the Earth and subsequent annihilation would yield a large flux at surface which could be seen in proton-decay detectors. The luminosity Uranus provides comparable constraints. Capture Sun can supplementary information, detectable signals possible for masses as low 6 GeV both Majorana neutrinos, photinos. discuss detail question evaporation, on results...

We study the onset of eigenstate thermalization in two-dimensional transverse field Ising model (2D-TFIM) square lattice. consider two nonequivalent Hamiltonians: ferromagnetic 2D-TFIM and antiferromagnetic presence a uniform longitudinal field. use full exact diagonalization to examine behavior quantum chaos indicators diagonal matrix elements operators interest eigenstates Hamiltonian. An analysis finite size effects reveals that occur those systems whenever fields are nonvanishing not too large.

We show that the known bound on growth rate of out-of-time-order four-point correlator in chaotic many-body quantum systems follows directly from general structure operator matrix elements obey eigenstate thermalization hypothesis. This ties together two key paradigms thermal behavior isolated systems.