4,193 research outputs found
Nonlocal compensation of pure phase objects with entangled photons
We suggest and demonstrate a scheme for coherent nonlocal compensation of
pure phase objects based on two-photon polarization and momentum entangled
states. The insertion of a single phase object on one of the beams reduces the
purity of the state and the amount of shared entanglement, whereas the original
entanglement can be retrieved by adding a suitable phase object on the other
beam. In our setup polarization and momentum entangled states are generated by
spontaneous parametric downconversion and then purified using a programmable
spatial light modulator, which may be also used to impose arbitrary space
dependent phase functions to the beams. As a possible application, we suggest
and demonstrate a quantum key distribution protocol based on nonlocal phase
compensation.Comment: 7 pages, 5 figure
The Axion and the Goldstone Higgs
We consider the renormalizable -model, in which the
Higgs particle has a pseudo-Nambu-Goldstone boson character, and explore what
the minimal field extension required to implement the Peccei-Quinn symmetry
(PQ) is, within the partial compositeness scenario. It turns out that the
minimal model does not require the enlargement of the exotic fermionic sector,
but only the addition of a singlet scalar: it is sufficient that the exotic
fermions involved in partial compositeness and the singlet scalar become
charged under Peccei-Quinn transformations. We explore the phenomenological
predictions for photonic signals in axion searches for all models discussed.
Because of the constraints imposed on the exotic fermion sector by the Standard
Model fermion masses, the expected range of allowed axion-photon couplings
turns out to be generically narrowed with respect to that of standard invisible
axion models, impacting the experimental quest.Comment: 31 pages, 2 Figures. Description improved, results unchange
Modification of magnetic and transport properties of manganite layers in Au/La_0.67Sr_0.33MnO_3/SrTiO_3 interfaces
The effect of gold capping on magnetic and transport properties of optimally
doped manganite thin films is studied. An extraordinary suppression of
conductivity and magnetic properties occurs in epitaxial (001)
La_0.67Sr_0.33MnO_3 (LSMO) films grown on SrTiO_3 upon deposition of 2 nm of
Au: in the case of ultrathin films of LSMO (4 nm thick) the resistivity
increases by four orders of magnitude while the Curie temperature decreases by
180 K. Zero-field 55Mn nuclear magnetic resonance reveals a significant
reduction of ferromagnetic double-exchange mechanism in manganite films upon
the gold capping. We find evidence for the formation of a 1.9-nm thick magnetic
"dead-layer" at the Au/LSMO interface, associated with the creation of
interfacial non double-exchange insulating phases.Comment: 4 figure
Higgs ultraviolet softening
We analyze the leading effective operators which induce a quartic momentum
dependence in the Higgs propagator, for a linear and for a non-linear
realization of electroweak symmetry breaking. Their specific study is relevant
for the understanding of the ultraviolet sensitivity to new physics. Two
methods of analysis are applied, trading the Lagrangian coupling by: i) a
"ghost" scalar, after the Lee-Wick procedure; ii) other effective operators via
the equations of motion. The two paths are shown to lead to the same effective
Lagrangian at first order in the operator coefficients. It follows a
modification of the Higgs potential and of the fermionic couplings in the
linear realization, while in the non-linear one anomalous quartic gauge
couplings, Higgs-gauge couplings and gauge-fermion interactions are induced in
addition. Finally, all LHC Higgs and other data presently available are used to
constrain the operator coefficients; the future impact of data via off-shell Higgs exchange and of vector boson fusion data is
considered as well. For completeness, a summary of pure-gauge and gauge-Higgs
signals exclusive to non-linear dynamics at leading-order is included.Comment: 31 pages, 3 figures, 7 table
Browsing Large Image Datasets through Voronoi Diagrams
Conventional browsing of image collections use mechanisms such as thumbnails arranged on a regular grid or on a line, often mounted over a scrollable panel. However, this approach does not scale well with the size of the datasets (number of images). In this paper, we propose a new thumbnail-based interface to browse large collections of images. Our approach is based on weighted centroidal anisotropic Voronoi diagrams.
A dynamically changing subset of images is represented by thumbnails and shown on the screen. Thumbnails are shaped like general polygons, to better cover screen space, while still reflecting the original aspect ratios or orientation of the represented images. During the browsing process, thumbnails are dynamically rearranged, reshaped and rescaled. The objective is to devote more screen space (more numerous and larger thumbnails) to the parts of the dataset closer to the current region of interest, and progressively lesser away from it, while still making the dataset visible as a whole. During the entire process, temporal coherence is always maintained. GPU implementation easily guarantees the frame rates needed for fully smooth interactivity
Kinetic study of an on-chip isocyanate derivatization reaction by on-line nano-esi ms
A high-throughput method is presented for the study of reaction kinetics by nano- electrospray ionization mass spectrometry (nano-ESI MS). The reaction of propyl isocyanate (2), benzyl isocyanate (3), and toluene-2,4-diisocyanate (4) with 4-nitro-7- piperazino-2,1,3-benzoxadiazole (NBDPZ) (1) to yield the corresponding urea derivatives (5) was carried out in a continuous flow glass microchip. Real-time monitoring of the reactions was done by nano-ESI MS. Rate constants of 1.6 ␣ 104 M-1 min-1, 5.2 ␣ 104 M-1 min-1, and 2.5 ␣ 104 M-1 min-1 were determined for isocyanate 2, 3 and 4, respectively
On the ab initio calculation of CVV Auger spectra in closed-shell systems
We propose an ab initio method to evaluate the core-valence-valence (CVV)
Auger spectrum of systems with filled valence bands. The method is based on the
Cini-Sawatzky theory, and aims at estimating the parameters by first-principles
calculations in the framework of density-functional theory (DFT). Photoemission
energies and the interaction energy for the two holes in the final state are
evaluated by performing DFT simulations for the system with varied population
of electronic levels. Transition matrix elements are taken from atomic results.
The approach takes into account the non-sphericity of the density of states of
the emitting atom, spin-orbit interaction in core and valence, and non
quadratic terms in the total energy expansion with respect to fractional
occupation numbers. It is tested on two benchmark systems, Zn and Cu metals,
leading in both cases to L23M45M45 Auger peaks within 2 eV from the
experimental ones. Detailed analysis is presented on the relative weight of the
various contributions considered in our method, providing the basis for future
development. Especially problematic is the evaluation of the hole-hole
interaction for systems with broad valence bands: our method underestimates its
value in Cu, while we obtain excellent results for this quantity in Zn.Comment: 20 pages, 5 figures, 4 table
Disentangling a dynamical Higgs
The pattern of deviations from Standard Model predictions and couplings is
different for theories of new physics based on a non-linear realization of the
gauge symmetry breaking and those assuming a linear
realization. We clarify this issue in a model-independent way via its effective
Lagrangian formulation in the presence of a light Higgs particle, up to first
order in the expansions: dimension-six operators for the linear expansion and
four derivatives for the non-linear one. Complete sets of pure gauge and
gauge-Higgs operators are considered, implementing the renormalization
procedure and deriving the Feynman rules for the non-linear expansion. We
establish the theoretical relation and the differences in physics impact
between the two expansions. Promising discriminating signals include the
decorrelation in the non-linear case of signals correlated in the linear one:
some pure gauge versus gauge-Higgs couplings and also between couplings with
the same number of Higgs legs. Furthermore, anomalous signals expected at first
order in the non-linear realization may appear only at higher orders of the
linear one, and vice versa. We analyze in detail the impact of both type of
discriminating signals on LHC physics.Comment: Version published in JHE
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