77 research outputs found
Travelling Randomly on the Poincar\'e Half-Plane with a Pythagorean Compass
A random motion on the Poincar\'e half-plane is studied. A particle runs on
the geodesic lines changing direction at Poisson-paced times. The hyperbolic
distance is analyzed, also in the case where returns to the starting point are
admitted. The main results concern the mean hyperbolic distance (and also the
conditional mean distance) in all versions of the motion envisaged. Also an
analogous motion on orthogonal circles of the sphere is examined and the
evolution of the mean distance from the starting point is investigated
Ultralocal Fields and their Relevance for Reparametrization Invariant Quantum Field Theory
Reparametrization invariant theories have a vanishing Hamiltonian and enforce
their dynamics through a constraint. We specifically choose the Dirac procedure
of quantization before the introduction of constraints. Consequently, for field
theories, and prior to the introduction of any constraints, it is argued that
the original field operator representation should be ultralocal in order to
remain totally unbiased toward those field correlations that will be imposed by
the constraints. It is shown that relativistic free and interacting theories
can be completely recovered starting from ultralocal representations followed
by a careful enforcement of the appropriate constraints. In so doing all
unnecessary features of the original ultralocal representation disappear.
The present discussion is germane to a recent theory of affine quantum
gravity in which ultralocal field representations have been invoked before the
imposition of constraints.Comment: 17 pages, LaTeX, no figure
Fundamentals of Quantum Gravity
The outline of a recent approach to quantum gravity is presented. Novel
ingredients include: (1) Affine kinematical variables; (2) Affine coherent
states; (3) Projection operator approach toward quantum constraints; (4)
Continuous-time regularized functional integral representation without/with
constraints; and (5) Hard core picture of nonrenormalizability. The ``diagonal
representation'' for operator representations, introduced by Sudarshan into
quantum optics, arises naturally within this program.Comment: 15 pages, conference proceeding
The Affine Quantum Gravity Program
The central principle of affine quantum gravity is securing and maintaining
the strict positivity of the matrix \{\hg_{ab}(x)\} composed of the spatial
components of the local metric operator. On spectral grounds, canonical
commutation relations are incompatible with this principle, and they must be
replaced by noncanonical, affine commutation relations. Due to the partial
second-class nature of the quantum gravitational constraints, it is
advantageous to use the recently developed projection operator method, which
treats all quantum constraints on an equal footing. Using this method,
enforcement of regularized versions of the gravitational operator constraints
is formulated quite naturally by means of a novel and relatively well-defined
functional integral involving only the same set of variables that appears in
the usual classical formulation. It is anticipated that skills and insight to
study this formulation can be developed by studying special, reduced-variable
models that still retain some basic characteristics of gravity, specifically a
partial second-class constraint operator structure. Although perturbatively
nonrenormalizable, gravity may possibly be understood nonperturbatively from a
hard-core perspective that has proved valuable for specialized models. Finally,
developing a procedure to pass to the genuine physical Hilbert space involves
several interconnected steps that require careful coordination.Comment: 16 pages, LaTeX, no figure
Cascades of Particles Moving at Finite Velocity in Hyperbolic Spaces
A branching process of particles moving at finite velocity over the geodesic
lines of the hyperbolic space (Poincar\'e half-plane and Poincar\'e disk) is
examined. Each particle can split into two particles only once at Poisson paced
times and deviates orthogonally when splitted. At time , after
Poisson events, there are particles moving along different geodesic
lines. We are able to obtain the exact expression of the mean hyperbolic
distance of the center of mass of the cloud of particles. We derive such mean
hyperbolic distance from two different and independent ways and we study the
behavior of the relevant expression as increases and for different values
of the parameters (hyperbolic velocity of motion) and (rate of
reproduction). The mean hyperbolic distance of each moving particle is also
examined and a useful representation, as the distance of a randomly stopped
particle moving over the main geodesic line, is presented
A Burgessian critique of nominalistic tendencies in contemporary mathematics and its historiography
We analyze the developments in mathematical rigor from the viewpoint of a
Burgessian critique of nominalistic reconstructions. We apply such a critique
to the reconstruction of infinitesimal analysis accomplished through the
efforts of Cantor, Dedekind, and Weierstrass; to the reconstruction of Cauchy's
foundational work associated with the work of Boyer and Grabiner; and to
Bishop's constructivist reconstruction of classical analysis. We examine the
effects of a nominalist disposition on historiography, teaching, and research.Comment: 57 pages; 3 figures. Corrected misprint
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