154 research outputs found
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
Multiphoton Transitions in a Spin System Driven by Strong Bichromatic Field
EPR transient nutation spectroscopy is used to measure the effective field
(Rabi frequency) for multiphoton transitions in a two-level spin system
bichromatically driven by a transverse microwave (MW) field and a longitudinal
radio-frequency (RF) field. The behavior of the effective field amplitude is
examined in the case of a relatively strong MW field, when the derivation of
the effective Hamiltonian cannot be reduced to first-order perturbation theory
in w_{1} / w_{rf} (w_{1} is the microwave Rabi frequency, w_{rf} is the RF
frequency). Experimental results are consistently interpreted by taking into
account the contributions of second and third order in w_{1} / w_{rf} evaluated
by Krylov-Bogolyubov-Mitropolsky averaging. In the case of inhomogeneously
broadened EPR line, the third-order correction modifies the nutation frequency,
while the second-order correction gives rise to a change in the nutation
amplitude due to a Bloch-Siegert shift.Comment: 7 pages, 6 figure
How the War in Ukraine Affects Food Security
The war in Ukraine has caused severe disruption to national and worldwide food supplies. Ukraine is a major exporter of wheat, maize, and oilseeds, staples that are now suffering a war-triggered supply risk. This paper describes the background of the problem and illustrates current trends by outlining some of the measures that may be deployed to mitigate the conflict’s impacts on achieving SDG 2 (Zero hunger), especially focusing on ending hunger, achieving food security, improving nutrition, and promoting sustainable agriculture. In order to understand the main research strands in the literature that are related to food security in the context of wars, the authors adopted a bibliometric literature review based on the co-occurrence of terms technique, conducted with 631 peer-reviewed documents extracted from the Scopus database. To complement the bibliometric assessment, ten case studies were selected to narrow down the food insecurity aspects caused by the war in Ukraine. The co-occurrence analysis indicated four different thematic clusters. In the next stage, an assessment of the current situation on how war affects food security was carried out for each one of the clusters, and the reasons and possible solutions to food security were identified. Policy recommendations and theoretical implications for food security in the conflict context in Ukraine were also addressed
Galilean Conformal and Superconformal Symmetries
Firstly we discuss briefly three different algebras named as nonrelativistic
(NR) conformal: Schroedinger, Galilean conformal and infinite algebra of local
NR conformal isometries. Further we shall consider in some detail Galilean
conformal algebra (GCA) obtained in the limit c equal to infinity from
relativistic conformal algebra O(d+1,2) (d - number of space dimensions). Two
different contraction limits providing GCA and some recently considered
realizations will be briefly discussed. Finally by considering NR contraction
of D=4 superconformal algebra the Galilei conformal superalgebra (GCSA) is
obtained, in the formulation using complex Weyl supercharges.Comment: 16 pages, LateX; talk presented at XIV International Conference
"Symmetry Methods in Physics", Tsakhkadzor, Armenia, August 16-22, 201
Superconformal Yang-Mills quantum mechanics and Calogero model with OSp(N|2,R) symmetry
In spacetime dimension two, pure Yang-Mills possesses no physical degrees of
freedom, and consequently it admits a supersymmetric extension to couple to an
arbitrary number, N say, of Majorana-Weyl gauginos. This results in (N,0) super
Yang-Mills. Further, its dimensional reduction to mechanics doubles the number
of supersymmetries, from N to N+N, to include conformal supercharges, and leads
to a superconformal Yang-Mills quantum mechanics with symmetry group
OSp(N|2,R). We comment on its connection to AdS_2 \times S^{N-1} and reduction
to a supersymmetric Calogero model.Comment: 1+28 pages, no figure; Refs added. To appear in JHE
Higher Spin Fields in Siegel Space, Currents and Theta Functions
Dynamics of four-dimensional massless fields of all spins is formulated in
the Siegel space of complex symmetric matrices. It is shown that
the unfolded equations of free massless fields, that have a form of
multidimensional Schrodinger equations, naturally distinguish between positive-
and negative-frequency solutions of relativistic field equations, i.e.
particles and antiparticles. Multidimensional Riemann theta functions are shown
to solve massless field equations in the Siegel space. We establish the
correspondence between conserved higher-spin currents in four-dimensional
Minkowski space and those in the ten-dimensional matrix space. It is shown that
global symmetry parameters of the current in the matrix space should be
singular to reproduce a nonzero current in Minkowski space. The \D-function
integral evolution formulae for 4d massless fields in the Fock-Siegel space are
obtained. The generalization of the proposed scheme to higher dimensions and
systems of higher ranks is considered.Comment: LaTeX, 38 pages, v.3: clarifications, acknowledgements and references
added, typos corrected, v.4: more comments and references added, typos
corrected, the version to appear in JHE
Kappa-deformed oscillators, the choice of star product and free kappa-deformed quantum fields
In order to obtain free kappa-deformed quantum fields (with c-number
commutators) we proposed new concept of kappa-deformed oscillator algebra [1]
and the modification of kappa-star product [2], implementing in the product of
two quantum fields the change of standard kappa-deformed mass-shell conditions.
We recall here that the kappa-deformed oscillators recently introduced in
[3]-[5] lie on standard kappa-deformed mass-shell. Firstly, we study
kappa-deformed fields with the standard kappa-star product, what implies that
in the oscillator algebra the corresponding kappa-deformed oscillators lie on
standard kappa-deformed mass-shell. We argue that for the kappa-deformed
algebra of such field oscillators which carry fourmomenta on kappa-deformed
mass-shell it is not possible to obtain the free quantum kappa-deformed fields
with the c-number commutators. Further, we study kappa-deformed quantum fields
with the modified kappa-star product which implies the modification of
kappa-deformed mass-shell. We obtain large class of kappa-deformed statistics
depending on six arbitrary functions which provides the c-number field
commutator functions. Such general class of kappa-oscillators can be described
as the kappa-deformation of standard oscillator algebra obtained by composing
general kappa-deformed multiplication with the deformation of the flip
operator.Comment: 21 pages;v3 more clearly exposed aims and results in the paper; the
version which will appear in Journ.Phys.
Weinberg propagator of a free massive particle with an arbitrary spin from the BFV-BRST path integral
The transition amplitude is obtained for a free massive particle of arbitrary
spin by calculating the path integral in the index-spinor formulation within
the BFV-BRST approach. None renormalizations of the path integral measure were
applied. The calculation has given the Weinberg propagator written in the
index-free form with the use of index spinor. The choice of boundary conditions
on the index spinor determines holomorphic or antiholomorphic representation
for the canonical description of particle/antiparticle spin.Comment: 31 pages, Latex, version published in Class. Quantum Gra
Fast optoelectric printing of plasmonic nanoparticles into tailored circuits
Plasmonic nanoparticles are able to control light at nanometre-scale by coupling electromagnetic fields to the oscillations of free electrons in metals. Deposition of such nanoparticles onto substrates with tailored patterns is essential, for example, in fabricating plasmonic structures for enhanced sensing. This work presents an innovative micro-patterning technique, based on optoelectic printing, for fast and straightforward fabrication of curve-shaped circuits of plasmonic nanoparticles deposited onto a transparent electrode often used in optoelectronics, liquid crystal displays, touch screens, etc. We experimentally demonstrate that this kind of plasmonic structure, printed by using silver nanoparticles of 40 nm, works as a plasmonic enhanced optical device allowing for polarized-color-tunable light scattering in the visible. These findings have potential applications in biosensing and fabrication of future optoelectronic devices combining the benefits of plasmonic sensing and the functionality of transparent electrodes
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