643 research outputs found
Spontaneous proton decay and the origin of Peccei-Quinn symmetry
We propose a new interpretation of Peccei-Quinn symmetry within the Standard
Model, identifying it with the axial symmetry i.e. . This new interpretation retains all the attractive
features of Peccei-Quinn solution to strong CP problem but in addition also
leads to several other new and interesting consequences. Owing to the
identification the axion also behaves
like Majoron inducing small seesaw masses for neutrinos after spontaneous
symmetry breaking. Another novel feature of this identification is the
phenomenon of spontaneous (and also chiral) proton decay with its decay rate
associated with the axion decay constant. Low energy processes which can be
used to test this interpretation are pointed out.Comment: 8 pages, 1 figure, a brief section on axial Baryon number as PQ
symmetry added, additional refs added, conclusions unchanged, published
versio
Energy Optimal Transmission Scheduling in Wireless Sensor Networks
One of the main issues in the design of sensor networks is energy efficient
communication of time-critical data. Energy wastage can be caused by failed
packet transmission attempts at each node due to channel dynamics and
interference. Therefore transmission control techniques that are unaware of the
channel dynamics can lead to suboptimal channel use patterns. In this paper we
propose a transmission controller that utilizes different "grades" of channel
side information to schedule packet transmissions in an optimal way, while
meeting a deadline constraint for all packets waiting in the transmission
queue. The wireless channel is modeled as a finite-state Markov channel. We are
specifically interested in the case where the transmitter has low-grade channel
side information that can be obtained based solely on the ACK/NAK sequence for
the previous transmissions. Our scheduler is readily implementable and it is
based on the dynamic programming solution to the finite-horizon transmission
control problem. We also calculate the information theoretic capacity of the
finite state Markov channel with feedback containing different grades of
channel side information including that, obtained through the ACK/NAK sequence.
We illustrate that our scheduler achieves a given throughput at a power level
that is fairly close to the fundamental limit achievable over the channel.Comment: Accepted for publication in the IEEE Transactions on Wireless
Communication
India: A New Player in Asian Production Networks?, Studies in Trade and Investment 75
Chapter IV includes case studies of the automotive components and electronics sectors in order to illustrate the potentially successful example of India emerging as an important regional player in Asian IPNs. The policy challenges and key recommendations for India to integrate into Asian IPNs are analysed.production network, fragmentation of production, Asia, value chain, China, India, PTAs
Signatures of New Physics from HBT Correlations in UHECRs
Quantum fields written on noncommutative spacetime (Groenewold - Moyal plane)
obey twisted commutation relations. In this paper we show that these twisted
commutation relations result in Hanbury-Brown Twiss (HBT) correlations that are
distinct from that for ordinary bosonic or fermionic fields, and hence can
provide us useful information about underlying noncommutative nature of
spacetime. The deviation from usual bosonic/fermionic statistics becomes
pronounced at high energies, suggesting that a natural place is to look at
Ultra High Energy Cosmic Rays (UHECRs). Since the HBT correlations are
sensitive only to the statistics of the particles, observations done with
UHECRs are capable of providing unambiguous signatures of noncommutativity,
without any detailed knowledge of the mechanism and source of origin of UHECRs.Comment: 8 pages, 4 figures, references and minor comments added, conclusions
unchanged, version to be published in Mod. Phys. Lett.
Phase stability and dynamics of entangled polymer-nanoparticle composites.
Nanoparticle-polymer composites, or polymer-nanoparticle composites (PNCs), exhibit unusual mechanical and dynamical features when the particle size approaches the random coil dimensions of the host polymer. Here, we harness favourable enthalpic interactions between particle-tethered and free, host polymer chains to create model PNCs, in which spherical nanoparticles are uniformly dispersed in high molecular weight entangled polymers. Investigation of the mechanical properties of these model PNCs reveals that the nanoparticles have profound effects on the host polymer motions on all timescales. On short timescales, nanoparticles slow-down local dynamics of the host polymer segments and lower the glass transition temperature. On intermediate timescales, where polymer chain motion is typically constrained by entanglements with surrounding molecules, nanoparticles provide additional constraints, which lead to an early onset of entangled polymer dynamics. Finally, on long timescales, nanoparticles produce an apparent speeding up of relaxation of their polymer host
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