3,551 research outputs found
Higher Spin Conformal Currents in Minkowski Space
Using unfolded formulation of free equations for massless fields of all spins
we obtain explicit form of higher-spin conformal conserved charges bilinear in
4d massless fields of arbitrary spins.Comment: LaTeX, 10 pages. Corrected typo
Holography of the N=1 Higher-Spin Theory on AdS4
We argue that the N=1 higher-spin theory on AdS4 is holographically dual to
the N=1 supersymmetric critical O(N) vector model in three dimensions. This
appears to be a special form of the AdS/CFT correspondence in which both
regular and irregular bulk modes have similar roles and their interplay leads
simultaneously to both the free and the interacting phases of the boundary
theory. We study various boundary conditions that correspond to boundary
deformations connecting, for large-N, the free and interacting boundary
theories. We point out the importance of parity in this holography and
elucidate the Higgs mechanism responsible for the breaking of higher-spin
symmetry for subleading N.Comment: 19 page
Acoustic characteristics of FeSe single crystals Acoustic characteristics of FeSe single crystals
The results of the comprehensive ultrasonic research of high quality single
crystals of FeSe are presented. Absolute values of sound velocities and their
temperature dependences were measured; elastic constants and Debye temperature
were calculated. The elastic C11-C12 and C11 constants undergo significant
softening under the structural tetra-ortho transformation. The significant
influence of the superconducting transition on the velocity and attenuation of
sound was revealed and the value of the superconducting energy gap was
estimated.Comment: 5 pages, 7 figures, 1 tabl
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
Magnetic ground state of FeSe
Elucidating the nature of the magnetism of a high-temperature superconductor
is crucial for establishing its pairing mechanism. The parent compounds of the
cuprate and iron-pnictide superconductors exhibit N\'eel and stripe magnetic
order, respectively. However, FeSe, the structurally simplest iron-based
superconductor, shows nematic order (Ts = 90 K), but not magnetic order in the
parent phase, and its magnetic ground state is intensely debated. Here, we
report inelastic neutron-scattering experiments that reveal both stripe and
N\'eel spin fluctuations over a wide energy range at 110 K. On entering the
nematic phase, a substantial amount of spectral weight is transferred from the
N\'eel to the stripe spin fluctuations. Moreover, the total fluctuating
magnetic moment of FeSe is ~ 60% larger than that in the iron pnictide
BaFe2As2. Our results suggest that FeSe is a novel S = 1 nematic
quantum-disordered paramagnet interpolating between the N\'eel and stripe
magnetic instabilities.Comment: Supplementary information included; accepted by Nature Communication
BTZ Black Hole as Solution of 3d Higher Spin Gauge Theory
BTZ black hole is interpreted as exact solution of 3d higher spin gauge
theory. Solutions for free massless fields in BTZ black hole background are
constructed with the help of the star-product algebra formalism underlying the
formulation of 3d higher spin theory. It is shown that a part of higher spin
symmetries remains unbroken for special values of the BTZ parameters.Comment: 31 pages, LaTeX; references correcte
Bifurcations and chaos in semiconductor superlattices with a tilted magnetic field
We study the effects of dissipation on electron transport in a semiconductor
superlattice with an applied bias voltage and a magnetic field that is tilted
relative to the superlattice axis.In previous work, we showed that although the
applied fields are stationary,they act like a THz plane wave, which strongly
couples the Bloch and cyclotron motion of electrons within the lowest miniband.
As a consequence,the electrons exhibit a unique type of Hamiltonian chaos,
which creates an intricate mesh of conduction channels (a stochastic web) in
phase space, leading to a large resonant increase in the current flow at
critical values of the applied voltage. This phase-space patterning provides a
sensitive mechanism for controlling electrical resistance. In this paper, we
investigate the effects of dissipation on the electron dynamics by modifying
the semiclassical equations of motion to include a linear damping term. We
demonstrate that even in the presence of dissipation,deterministic chaos plays
an important role in the electron transport process. We identify mechanisms for
the onset of chaos and explore the associated sequence of bifurcations in the
electron trajectories. When the Bloch and cyclotron frequencies are
commensurate, complex multistability phenomena occur in the system. In
particular, for fixed values of the control parameters several distinct stable
regimes can coexist, each corresponding to different initial conditions. We
show that this multistability has clear, experimentally-observable, signatures
in the electron transport characteristics.Comment: 14 pages 11 figure
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