9,190 research outputs found
Geometric Low-Energy Effective Action in a Doubled Spacetime
The ten-dimensional supergravity theory is a geometric low-energy effective
theory and the equations of motion for its fields can be obtained from string
theory by computing functions. With compact dimensions, we can add
to it an geometric structure and construct the
supergravity theory inspired by double field theory through the use of a
suitable commutative star product. The latter implements the weak constraint of
the double field theory on its fields and gauge parameters in order to have a
closed gauge symmetry algebra. The consistency of the action here proposed is
based on the orthogonality of the momenta associated with fields in their
triple star products in the cubic terms defined for . This orthogonality
holds also for an arbitrary number of star products of fields for .
Finally, we extend our analysis to the double sigma model, non-commutative
geometry and open string theory.Comment: 27 pages, minor changes, references adde
Photon-assisted Landau-Zener transition: Role of coherent superposition states
We investigate a Landau-Zener (LZ) transition process modeled by a quantum
two-level system (TLS) coupled to a photon mode when the bias energy is varied
linearly in time. The initial state of the photon field is assumed to be a
superposition of coherent states, leading to a more intricate LZ transition.
Applying the rotating-wave approximation (RWA), analytical results are obtained
revealing the enhancement of the LZ probability by increasing the average
photon number. We also consider the creation of entanglement and the change of
photon statistics during the LZ process. Without the RWA, we find some
qualitative differences of the LZ dynamics from the RWA results, e.g., the
average photon number no longer monotonically enhances the LZ probability. The
ramifications and implications of these results are explored.Comment: 9 pages, 7 figure
Spin Squeezing under Non-Markovian Channels by Hierarchy Equation Method
We study spin squeezing under non-Markovian channels, and consider an
ensemble of independent spin-1/2 particles with exchange symmetry. Each
spin interacts with its own bath, and the baths are independent and identical.
For this kind of open system, the spin squeezing under decoherence can be
investigated from the dynamics of the local expectations, and the multi-qubit
dynamics can be reduced into the two-qubit one. The reduced dynamics is
obtained by the hierarchy equation method, which is a exact without
rotating-wave and Born-Markov approximation. The numerical results show that
the spin squeezing displays multiple sudden vanishing and revival with lower
bath temperature, and it can also vanish asymptotically.Comment: 7 pages, 4 figure
Genome-wide profiling of uncapped mRNA
Gene transcripts are under extensive posttranscriptional regulation, including the regulation of their
stability. A major route for mRNA degradation produces uncapped mRNAs, which can be generated by
decapping enzymes, endonucleases, and small RNAs. Profiling uncapped mRNA molecules is important for
the understanding of the transcriptome, whose composition is determined by a balance between mRNA
synthesis and degradation. In this chapter, we describe a method to profile these uncapped mRNAs at the
genome scale
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