16,353 research outputs found
Evolution of Primordial Black Hole Mass Spectrum in Brans-Dicke Theory
We investigate the evolution of primordial black hole mass spectrum by
including both accretion of radiation and Hawking evaporation within
Brans-Dicke cosmology in radiation, matter and vacuum-dominated eras. We also
consider the effect of evaporation of primordial black holes on the expansion
dynamics of the universe. The analytic solutions describing the energy density
of the black holes in equilibrium with radiation are presented. We demonstrate
that these solutions act as attractors for the system ensuring stability for
both linear and nonlinear situations. We show, however, that inclusion of
accretion of radiation delays the onset of this equilibrium in all radiation,
matter and vacuum-dominated eras.Comment: 18 pages, one figur
Entanglement measurement with discrete multiple coin quantum walks
Within a special multi-coin quantum walk scheme we analyze the effect of the
entanglement of the initial coin state. For states with a special entanglement
structure it is shown that this entanglement can be meausured with the mean
value of the walk, which depends on the i-concurrence of the initial coin
state. Further on the entanglement evolution is investigated and it is shown
that the symmetry of the probability distribution is reflected by the symmetry
of the entanglement distribution.Comment: 9 pages, IOP styl
Analysis of stability parameters in relation to precipitation associated with pre-monsoon thunderstorms over Kolkata, India
The upper air RS/RW (Radio Sonde/Radio Wind) observations at Kolkata (22.65 N, 88.45 E) during premonsoon season March–May, 2005–2012 is used to compute some important dynamic/thermodynamic parameters and are analysed in relation to the precipitation associated with the thunderstorms over Kolkata, India. For this purpose, the pre-monsoon thunderstorms are classified as Light Precipitation (LP), Moderate Precipitation (MP) and Heavy Precipitation (HP) thunderstorms based on the magnitude of associated precipitation. Richardson number in non-uniformly saturated atmosphere (Ri*)well indicate the occurrence of thunderstorms about 2 hours in advance. Moderate vertical wind shear in lower troposphere (0–3 km) and weak shear in middle troposphere (3–7 km) leads to heavy precipitation thunderstorms. The wind shear in 3–7 km atmospheric layers, EHI and VGP are good predictors of precipitation associated with thunderstorm. Lower tropospheric wind shear and Richardson number is a poor discriminator of the three classified thunderstorms
Hybrid Quantum System of a Nanofiber Mode Coupled to Two Chains of Optically Trapped Atoms
A tapered optical nanofiber simultaneously used to trap and optically
interface of cold atoms through evanescent fields constitutes a new and well
controllable hybrid quantum system. The atoms are trapped in two parallel 1D
optical lattices generated by suitable far blue and red detuned evanescent
field modes very close to opposite sides of the nanofiber surface. Collective
electronic excitations (excitons) of each of the optical lattices are
resonantly coupled to the second lattice forming symmetric and antisymmetric
common excitons. In contrast to the inverse cube dependence of the individual
atomic dipole-dipole interaction, we analytically find an exponentially
decaying coupling strength with distance between the lattices. The resulting
symmetric (bright) excitons strongly interact with the resonant nanofiber
photons to form fiber polaritons, which can be observed through linear optical
spectra. For large enough wave vectors the polariton decay rate to free space
is strongly reduced, which should render this system ideal for the realization
of long range quantum communication between atomic ensembles.Comment: 9 pages, 9 figure
Zero-Shot Learning with Common Sense Knowledge Graphs
Zero-shot learning relies on semantic class representations such as
hand-engineered attributes or learned embeddings to predict classes without any
labeled examples. We propose to learn class representations from common sense
knowledge graphs. Common sense knowledge graphs are an untapped source of
explicit high-level knowledge that requires little human effort to apply to a
range of tasks. To capture the knowledge in the graph, we introduce ZSL-KG, a
general-purpose framework with a novel transformer graph convolutional network
(TrGCN) for generating class representations. Our proposed TrGCN architecture
computes non-linear combinations of the node neighbourhood and shows
improvements on zero-shot learning tasks in language and vision. Our results
show ZSL-KG outperforms the best performing graph-based zero-shot learning
framework by an average of 2.1 accuracy points with improvements as high as 3.4
accuracy points. Our ablation study on ZSL-KG with alternate graph neural
networks shows that our TrGCN adds up to 1.2 accuracy points improvement on
these tasks
Comment on "Probabilistic Quantum Memories"
This is a comment on two wrong Phys. Rev. Letters papers by C.A.
Trugenberger. Trugenberger claimed that quantum registers could be used as
exponentially large "associative" memories. We show that his scheme is no
better than one where the quantum register is replaced with a classical one of
equal size.
We also point out that the Holevo bound and more recent bounds on "quantum
random access codes" pretty much rule out powerful memories (for classical
information) based on quantum states.Comment: REVTeX4, 1 page, published versio
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