10,006 research outputs found
A preliminary study on the affinities of Philippine, Bornean and New Guinean hepatics
The generic and specific affinities of the Philippine, Bornean and New Guinean hepatic floras were analyzed by calculating the Kroeber's percentage of similarity on the basis of recently published checklists. It is observed that the overall affinities parallel that exhibited by local moss floras except for one important difference. For the three areas, the number and distribution of species of large, actively evolving hepatic genera are noted to be disparate and with few shared taxa. Contrastingly, the large and actively evolving moss genera produce consistently large number of species in all three areas with an equally large number of shared taxa. The strong dependence of many hepatic taxa on asexual reproduction and the poor spore dispersability are accepted as the best explanation to this phenomenon
Efficiency of Human Activity on Information Spreading on Twitter
Understanding the collective reaction to individual actions is key to
effectively spread information in social media. In this work we define
efficiency on Twitter, as the ratio between the emergent spreading process and
the activity employed by the user. We characterize this property by means of a
quantitative analysis of the structural and dynamical patterns emergent from
human interactions, and show it to be universal across several Twitter
conversations. We found that some influential users efficiently cause
remarkable collective reactions by each message sent, while the majority of
users must employ extremely larger efforts to reach similar effects. Next we
propose a model that reproduces the retweet cascades occurring on Twitter to
explain the emergent distribution of the user efficiency. The model shows that
the dynamical patterns of the conversations are strongly conditioned by the
topology of the underlying network. We conclude that the appearance of a small
fraction of extremely efficient users results from the heterogeneity of the
followers network and independently of the individual user behavior.Comment: 29 pages, 10 figure
Echo of the Quantum Bounce
We identify a signature of quantum gravitational effects that survives from
the early universe to the current era: Fluctuations of quantum fields as seen
by comoving observers are significantly influenced by the history of the early
universe. In particular we show how the existence (or not) of a quantum bounce
leaves a trace in the background quantum noise that is not damped and would be
non-negligible even nowadays. Furthermore, we estimate an upper bound for the
typical energy and length scales where quantum effects are relevant. We discuss
how this signature might be observed and therefore used to build falsifiability
tests of quantum gravity theories.Comment: Revtex4.1. 2 Figures. V2: Content extended and edited to match
published versio
Input-output theory for spin-photon coupling in Si double quantum dots
The interaction of qubits via microwave frequency photons enables
long-distance qubit-qubit coupling and facilitates the realization of a
large-scale quantum processor. However, qubits based on electron spins in
semiconductor quantum dots have proven challenging to couple to microwave
photons. In this theoretical work we show that a sizable coupling for a single
electron spin is possible via spin-charge hybridization using a magnetic field
gradient in a silicon double quantum dot. Based on parameters already shown in
recent experiments, we predict optimal working points to achieve a coherent
spin-photon coupling, an essential ingredient for the generation of long-range
entanglement. Furthermore, we employ input-output theory to identify observable
signatures of spin-photon coupling in the cavity output field, which may
provide guidance to the experimental search for strong coupling in such
spin-photon systems and opens the way to cavity-based readout of the spin
qubit
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