6,556 research outputs found
Effect of hyperon-hyperon interaction on bulk viscosity and r-mode instability in neutron stars
We investigate the effect of hyperon matter including hyperon-hyperon
interaction on bulk viscosity. Equations of state are constructed within the
framework of a relativistic field theoretical model where baryon-baryon
interaction is mediated by the exchange of scalar and vector mesons.
Hyperon-hyperon interaction is also taken into account by the exchange of two
strange mesons. This interaction results in a smaller maximum mass neutron star
compared with the case without the interaction. The coefficient of bulk
viscosity due to the non-leptonic weak process is determined by these equations
of state. The interacting hyperon matter reduces the bulk viscosity coefficient
in a neutron star interior compared with the no interaction case. The r-mode
instability is more effectively suppressed in hyperon-hyperon interaction case
than that without the interaction.Comment: 25 pages, 10 figures; two new figures added and results and
discussion section revised; final version to appear in PR
Floquet analysis of pulsed Dirac systems: A way to simulate rippled graphene
The low energy continuum limit of graphene is effectively known to be modeled
using Dirac equation in (2+1) dimensions. We consider the possibility of using
modulated high frequency periodic driving of a two-dimension system (optical
lattice) to simulate properties of rippled graphene. We suggest that the Dirac
Hamiltonian in a curved background space can also be effectively simulated by a
suitable driving scheme in optical lattice. The time dependent system yields,
in the approximate limit of high frequency pulsing, an effective time
independent Hamiltonian that governs the time evolution, except for an initial
and a final kick. We use a specific form of 4-phase pulsed forcing with
suitably tuned choice of modulating operators to mimic the effects of
curvature. The extent of curvature is found to be directly related to
the time period of the driving field at the leading order. We
apply the method to engineer the effects of curved background space. We find
that the imprint of curvilinear geometry modifies the electronic properties,
such as LDOS, significantly. We suggest that this method shall be useful in
studying the response of various properties of such systems to non-trivial
geometry without requiring any actual physical deformations.Comment: 16 pages, 1 figure. Suggestions and comments are welcom
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