32,662 research outputs found
Cosmological Vorticity in a Gravity with Quadratic Order Curvature Couplings
We analyse the evolution of the rotational type cosmological perturbation in
a gravity with general quadratic order gravitational coupling terms. The result
is expressed independently of the generalized nature of the gravity theory, and
is simply interpreted as a conservation of the angular momentum.Comment: 5 pages, revtex, no figure
Cosmological perturbations in a generalized gravity including tachyonic condensation
We present unified ways of handling the cosmological perturbations in a class
of gravity theory covered by a general action in eq. (1). This gravity includes
our previous generalized gravity and the gravity theory motivated
by the tachyonic condensation. We present general prescription to derive the
power spectra generated from vacuum quantum fluctuations in the slow-roll
inflation era. An application is made to a slow-roll inflation based on the
tachyonic condensation with an exponential potential.Comment: 5 page
Efficient Schemes for Reducing Imperfect Collective Decoherences
We propose schemes that are efficient when each pair of qubits undergoes some
imperfect collective decoherence with different baths. In the proposed scheme,
each pair of qubits is first encoded in a decoherence-free subspace composed of
two qubits. Leakage out of the encoding space generated by the imperfection is
reduced by the quantum Zeno effect. Phase errors in the encoded bits generated
by the imperfection are reduced by concatenation of the decoherence-free
subspace with either a three-qubit quantum error correcting code that corrects
only phase errors or a two-qubit quantum error detecting code that detects only
phase errors, connected with the quantum Zeno effect again.Comment: no correction, 3 pages, RevTe
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