623 research outputs found
The shape of the Galactic halo with DR2 RR Lyrae. Anatomy of an ancient major merger
We use the DR2 RR Lyrae sample to gain an uninterrupted view of the
Galactic stellar halo. We dissect the available volume in slices parallel to
the Milky Way's disc to show that within kpc from the Galactic centre
the halo is triaxial, with the longest axis misaligned by with
respect to the Galactic -axis. This anatomical procedure exposes two large
diffuse over-densities aligned with the semi-major axis of the halo: the
Hercules-Aquila Cloud and the Virgo Over-density. We reveal the kinematics of
the entire inner halo by mapping out the amplitudes and directions of the RR
Lyrae proper motions. These are then compared to simple models with different
anisotropies to demonstrate that the inner halo is dominated by stars on highly
eccentric orbits. We interpret the shape of the density and the kinematics of
the DR2 RR Lyrae as evidence in favour of a scenario in which the bulk
of the halo was deposited in a single massive merger event.Comment: 12 pages, 7 figures; Accepted for publication in MNRA
The Exact Solution of the Schwarzian Theory
The explicit evaluation of the partition function in the Schwarzian theory is
presented.Comment: 3 page
Correlation functions in the Schwarzian theory
A mathematically correct approach to study theories with infinite-dimensional
groups of symmetries is presented. It is based on quasi-invariant measures on
the groups. In this paper, the properties of the measure on the group of
diffeomorphisms are used to evaluate the functional integrals in the Schwarzian
theory. As an important example of the application of the new technique, we
explicitly evaluate the correlation functions in the Schwarzian theory.Comment: 29 pages, 3 figure
A quantum mechanical model of "dark matter"
The role of singular solutions in some simple quantum mechanical models is
studied. The space of the states of two-dimensional quantum harmonic oscillator
is shown to be separated into sets of states with different properties.Comment: 9 pages, LaTex, 4 figure
Paths with singularities in functional integrals of quantum field theory
In the toy model (-interacting quantum field theory in
one-dimensional "Euclidean" space-time) we prove that the functional integrals
of the free field theory evaluated over the space of continuous functions are
equal to the functional integrals of the interacting field theory evaluated
over a set of spaces containing the spaces of discontinuous functions
Quantum restoration of broken symmetries
A certain non-linear non-local substitution is shown to transform the action
of the self-interacting quantum field to the free one. The functional integrals
in both theories are equal to each other. However, the integrations are
performed over different functional spaces. The classical action and the
classical limit of the corresponding quantum theory turn out to be different.
And the symmetry originally broken in the classical theory is restored in the
classical limit of the quantum theory.Comment: LaTex 5 page
Peculiar spaces of relativistic quantum fields
We study how quantum field theory models are modified under the
reparametrizations of the space-time coordinates and some simultaneous
transformations of the field function. The transformations that turn the action
of the massive field in the Minkowski space-time into the action of the
massless field in some curved space are presented.Comment: 7 page
On the local limit of quantum field theories defined on the loop space
The local limit of a quantum field theory on the loop space is studied. It is
proved that the invariance of the theory with respect to the group of
diffeomorphisms leads to Feynman diagrams convergence in the local limit
A class of exactly solvable quantum models of scalar gravity
Exactly solvable quantum theory of a singular at the origin scalar field with
the self-interaction of Liouville type is proposed. The mean value of the scale
factor in the FLRW metric as a function of conformal time is evaluated
explicitly.Comment: 5 page
A Prototype for Science Alerts
Many of the science goals of the GAIA mission, especially for bursting or
time-varying phenomena like supernovae or microlensing, require an early
identification, analysis and release of preliminary data. The alerting on rare
and unusual events is the scientific equivalent of the finding of needles in
haystacks or the panning for gold-dust in rivers. In modern signal processing,
such novelty detection is routinely performed with self-organising maps (SOMs),
which are an unsupervised clustering algorithm invented by Kohonen. Here, we
describe the application of SOMS to the classification of data provided by
large-scale surveys such as GAIA and to the despatching of scientific alerts.
We illustrate our ideas by processing the publically available OGLE II dataset
towards the Bulge, identifying major classes of variable stars (such as novae,
small amplitude red giant variables, eclipsing binaries and so on) and
extracting the rare, discrepant lightcurves from which the alerts can be drawn.Comment: 8 pages, 10 figures, invited review for "The Three Dimensional
Universe with GAIA", eds M. Perryman, C. Turon (ESA SP-576
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