399 research outputs found
Extension of the Shirafuji model for Massive Particles with Spin
We extend the Shirafuji model for massless particles with primary spacetime
coordinates and composite four-momenta to a model for massive particles with
spin and electric charge. The primary variables in the model are the spacetime
four-vector, four scalars describing spin and charge degrees of freedom as well
as a pair of Weyl spinors. The geometric description proposed in this paper
provides an intermediate step between the free purely twistorial model in
two-twistor space in which both spacetime and four-momenta vectors are
composite, and the standard particle model, where both spacetime and
four-momenta vectors are elementary. We quantize the model and find explicitly
the first-quantized wavefunctions describing relativistic particles with mass,
spin and electric charge. The spacetime coordinates in the model are not
commutative; this leads to a wavefunction that depends only on one covariant
projection of the spacetime four-vector (covariantized time coordinate)
defining plane wave solutions.Comment: Latex, 27 pages, appendix.sty, newlfont.sty (attached
Twistorial versus space--time formulations: unification of various string models
We introduce the D=4 twistorial tensionfull bosonic string by considering the
canonical twistorial 2--form in two--twistor space. We demonstrate its
equivalence to two bosonic string models: due to Siegel (with covariant
worldsheet vectorial string momenta ) and the one with
tensorial string momenta . We show how to obtain in
mixed space-time--twistor formulation the Soroka--Sorokin--Tkach--Volkov (SSTV)
string model and subsequently by harmonic gauge fixing the Bandos--Zheltukhin
(BZ) model, with constrained spinorial coordinates.Comment: RevTex4,APS, 4 pages. The version which appears in Phys. Rev.
New Model of Higher-Spin Particle
We elaborate on a new model of the higher-spin (HS) particle which makes
manifest the classical equivalence of the HS particle of the unfolded
formulation and the HS particle model with a bosonic counterpart of
supersymmetry. Both these models emerge as two different gauges of the new
master system. Physical states of the master model are massless HS multiplets
described by complex HS fields which carry an extra U(1) charge q. The latter
fully characterizes the given multiplet by fixing the minimal helicity as q/2.
We construct the twistorial formulation of the master model and discuss
symmetries of the new HS multiplets within its framework.Comment: 13 pages, talk given by E. Ivanov at the XII International Conference
on Symmetry Methods in Physics (SYMPHYS-XII), Yerevan, Armenia, July 03 - 08,
2006; to be published in the Proceeding
Master Higher-Spin Particle
We propose a "master" higher-spin (HS) particle system. The particle model
relevant to the unfolded formulation of HS theory, as well as the HS particle
model with a bosonic counterpart of supersymmetry, follow from the master model
as its two different gauges. Quantization of the master system gives rise to a
new form of the massless HS equations in an extended space involving, besides
extra spinorial coordinates, also a complex scalar one. As solutions to these
equations we recover the massless HS multiplet with fields of all integer and
half-integer helicities, and obtain new multiplets with a non-zero minimal
helicity. The HS multiplets are described by complex wave functions which are
holomorphic in the scalar coordinate and carry an extra U(1) charge q. The
latter fully characterizes the given multiplet by fixing the minimal helicity
as q/2. We construct a twistorial formulation of the master system and present
the general solution of the associate HS equations through an unconstrained
twistor "prepotential".Comment: 21 pages, minor corrections, version to appear in Class. Quantum Gra
Purely twistorial string with canonical twistor field quantization
We introduce new purely twistorial scale-invariant action describing the
composite bosonic D=4 Nambu-Goto string with target space parametrized by the
pair of D=4 twistors. We show that by suitable gauge fixing of local scaling
one gets the bilinear twistorial action and canonical quantization rules for
the two-dimensional twistor-string fields. We consider the Poisson brackets of
all constraints characterizing our model and we obtain four first class
constraints describing two Virasoro constraints and two U(1)xU(1) Kac-Moody
(KM) local phase transformations.Comment: v3: 6p.(extended version), in press in Physical Review
New Super Calogero Models and OSp(4|2) Superconformal Mechanics
We report on the new approach to constructing superconformal extensions of
the Calogero-type systems with an arbitrary number of involved particles. It is
based upon the superfield gauging of non-abelian isometries of some
supersymmetric matrix models. Among its applications, we focus on the new N=4
superconformal system yielding the U(2) spin Calogero model in the bosonic
sector, and the one-particle case of this system, which is a new OSp(4|2)
superconformal mechanics with non-dynamical U(2) spin variables. The
characteristic feature of these models is that the strength of the conformal
inverse-square potential is quantized.Comment: 12 pages, talk presented by E.Ivanov at the XIII International
Conference "Symmetry Methods in Physics", Dubna, July 6-9, 200
Two-twistor particle models and free massive higher spin fields
We present D=3 and D=4 models for massive particles moving in a new type of
enlarged spacetime, with D-1 additional vector coordinates, which after
quantization lead to the towers of massive higher spin (HS) free fields. Two
classically equivalent formulations are presented: one with a hybrid
spacetime/bispinor geometry and a second described by a free two-twistor
dynamics with constraints. After quantization in the D=3 and D=4 cases, the
wave functions are given as functions on the SL(2,R) and SL(2,C) group
manifolds respectively, and describe arbitrary on-shell momenta and spin
degrees of freedom. Finally, the D=6 case and possible supersymmetric
extensions are mentioned.Comment: 37 pages, plain latex, v2. Text in Secs. 1 nd 4 enlarged, references
added. Version to appear in JHE
- …