4,340 research outputs found
Fluid Dynamics of NSR Strings
We show that the renormalization group flows of the massless superstring
modes in the presence of fluctuating D-branes satisfy the equations of fluid
dynamics.In particular, we show that the D-brane's U(1) field is related to the
velocity function in the Navier-Stokes equation while the dilaton plays the
role of the passive scalar advected by the turbulent flow. This leads us to
suggest a possible isomorphism between the off-shell superstring theory in the
presence of fluctuating branes and the fluid mechanical degrees of freedom.Comment: 24 pages Dedicated to the memory of Ian Koga
Interaction of Discrete States in Two-Dimensional String Theory
We study the couplings of discrete states that appear in the string theory
embedded in two dimensions, and show that they are given by the structure
constants of the group of area preserving diffeomorphisms. We propose an
effective action for these states, which is itself invariant under this
infinite-dimensional group.Comment: 12 page
Effects of Strain coupling and Marginal dimensionality in the nature of phase transition in Quantum paraelectrics
Here a recently observed weak first order transition in doped SrTiO3 is
argued to be a consequence of the coupling between strain and order parameter
fluctuations. Starting with a semi-microscopic action, and using
renormalization group equations for vertices, we write the free energy of such
a system. This fluctuation renormalized free energy is then used to discuss the
possibility of first order transition at zero temperature as well as at finite
temperature. An asymptotic analysis predicts small but a finite discontinuity
in the order parameter near a mean field quantum critical point at zero
temperature. In case of finite temperature transition, near quantum critical
point such a possibility is found to be extremely weak. Results are in accord
with some experimental findings on quantum paraelectrics such as SrTiO3 and
KTaO3.Comment: Revised versio
Theory of the fractional microwave-induced resistance oscillations
We develop a systematic theory of microwave-induced oscillations in
magnetoresistivity of a 2D electron gas in the vicinity of fractional harmonics
of the cyclotron resonance, observed in recent experiments. We show that in the
limit of well-separated Landau levels the effect is dominated by a change of
the distribution function induced by multiphoton processes. At moderate
magnetic field, a single-photon mechanism originating from the
microwave-induced sidebands in the density of states of disorder-broadened
Landau levels becomes important.Comment: 4 pages, 2 figures; V2: published version (typos corrected,
references added and updated
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