272 research outputs found
Topological transformations of speckles
Deterministic control of coherent random light is highly important for
information transmission through complex media. However, only a few simple
speckle transformations can be achieved through diffusers without prior
characterization. As recently shown, spiral wavefront modulation of the
impinging beam allows permuting intensity maxima and intrinsic -charged
optical vortices. Here, we study this cyclic-group algebra when combining
spiral phase transforms of charge , with - and -point-group
symmetry star-like amplitude modulations. This combination allows statistical
strengthening of permutations and controlling the period to be 3 and 4,
respectively. Phase saddle-points are shown to complete the cycle. These
results offer new tools to manipulate critical points in speckles.Comment: 14 pages, 10 figures, 4 table
Relation between o-equivalence and EA-equivalence for Niho bent functions
Boolean functions, and bent functions in particular, are considered up to so-called EA-equivalence, which is the most general known equivalence relation preserving bentness of functions. However, for a special type of bent functions, so-called Niho bent functions there is a more general equivalence relation called o-equivalence which is induced from the equivalence of o-polynomials. In the present work we study, for a given o-polynomial, a general construction which provides all possible o-equivalent Niho bent functions, and we considerably simplify it to a form which excludes EA-equivalent cases. That is, we identify all cases which can potentially lead to pairwise EA-inequivalent Niho bent functions derived from o-equivalence of any given Niho bent function. Furthermore, we determine all pairwise EA-inequivalent Niho bent functions arising from all known o-polynomials via o-equivalence.publishedVersio
Spectrum of collective excitations of a quantum fluid of polaritons
We use a recently developed high-resolution coherent probe spectroscopy
method to investigate the dispersion of collective excitations of a polaritonic
quantum fluid. We measure the dispersion relation with high energy and
wavenumber resolution, which allows us to determine the speed of sound in the
fluid and to evidence the contribution of an excitonic reservoir. We report on
the generation of collective excitations at negative energies, on the ghost
branch of the dispersion curve. Precursors of dynamical instabilities are also
identified. Our methods open the way to the precise study of quantum
hydrodynamics of quantum fluids of light
Observation of the diffusive Nambu-Goldstone mode of a non-equilibrium phase transition
Second-order phase transitions are governed by spontaneous symmetry breaking,
which yield collective excitations with a gapless spectrum called
Nambu-Goldstone (NG) modes. While NG modes in conservative systems are
propagating excitations, non-equilibrium phase transitions have been predicted
to feature a diffusive NG mode. We present the first experimental evidence of a
diffusive NG mode in a non-equilibrium Bose-Einstein condensate of microcavity
polaritons. The NG mode is observed as a spectral narrowing in the
spectroscopic response of the condensate. Additionally, explicitly breaking the
symmetry causes the opening of a gap in the spectrum and the disappearance of
the NG mode. Our observations confirm the diffusive dynamics of the NG mode of
non-equilibrium phase transitions and establish a promising framework to
investigate fundamental questions in statistical mechanics.Comment: 8 pages + refs + appendix, 6 figure
Spontaneous generation, enhanced propagation and optical imprinting of quantized vortices and dark solitons in a polariton superfluid: towards the control of quantum turbulence
In resonantly pumped polariton superfluids we recently explored a new regime
based on the bistability of the polariton system to enhance the propagation of
polariton fluids up to macroscopic distances. This technique together with an
all-optical imprinting method allowed the generation and control of various
topological excitations such as quantized vortices and dark solitons. The
flexibility and scalability of the new experimental scheme opens the way to the
systematic study of quantum turbulence in driven dissipative quantum fluids of
light. In this article we review the basic working principles of the
bistability enhanced propagation and of the imprinting technique and we discuss
the main achieved results as well as the most promising future research
directions.Comment: Review, 12 pages, 16 figure
Relation between o-equivalence and EA-equivalence for Niho bent functions
Boolean functions, and bent functions in particular, are considered up to so-called EA-equivalence, which is the most general known equivalence relation preserving bentness of functions.
However, for a special type of bent functions, so-called Niho bent functions there is a more general equivalence relation called o-equivalence which is induced from the equivalence of o-polynomials.
In the present work we study, for a given o-polynomial, a general construction which provides all possible o-equivalent Niho bent functions, and we considerably simplify it to a form which excludes EA-equivalent cases.
That is, we identify all cases which can potentially lead to pairwise EA-inequivalent Niho bent functions derived from o-equivalence of any given Niho bent function. Furthermore, we determine all pairwise EA-inequivalent Niho bent functions arising from all known o-polynomials via o-equivalence
"La sensación de la soledad" en las Rimas de Bécquer (Aproximación a la poesía metafísica)
In our article we try to approximate to the topic of Spanish romanticism and the cosmovision of Gustavo Adolfo Bécquer in particular. We evaluate the role of universal romantic symptom – the feeling of loneliness in Bécquer’s Rimas and observe how his poetic world is linked to the existensial vision of Miguel de Unamuno.En nuestro artículo intentamos acercarnos al tema del romanticismo español, y a la visión romántica de Gustavo Adolfo Bécquer en particular. Dentro de ello investigamos el papel del síntoma universal del romanticismo – la sensación de la soledad en las Rimas de Bécquer y observamos cómo está vinculado su mundo romántico con la visión existencialista de Miguel de Unamuno
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