1,122,262 research outputs found
Apparatus for recovering matter adhered to a host surface
The development of an apparatus for removing and recovering matter adhered to a host surface is described. The device consists of a pickup head with an ultrasonic transducer adapted to deliver ultrasonic pressure waves against the material. The ultrasonic waves agitate the material and cause its separation from the surface. A vacuum system recovers the material and delivers it to suitable storage containers
How bio-friendly is the universe
The oft-repeated claim that life is written into the laws of nature are
examined and criticized. Arguments are given in favour of life spreading
between near-neighbour planets in rocky impact ejecta (transpermia), but
against panspermia, leading to the conclusion that if life is indeed found to
be widespread in the universe, some form of life principle or biological
determinism must be at work in the process of biogenesis. Criteria for what
would constitute a credible life principle are elucidated. I argue that the key
property of life is its information content, and speculate that the emergence
of the requisite information-processing machinery might require quantum
information theory for a satisfactory explanation. Some clues about how
decoherence might be evaded are discussed. The implications of some of these
ideas for fine tuning are discussed.Comment: 11 page conference report, no figure
Quantum mechanics and the equivalence principle
A quantum particle moving in a gravitational field may penetrate the
classically forbidden region of the gravitational potential. This raises the
question of whether the time of flight of a quantum particle in a gravitational
field might deviate systematically from that of a classical particle due to
tunnelling delay, representing a violation of the weak equivalence principle. I
investigate this using a model quantum clock to measure the time of flight of a
quantum particle in a uniform gravitational field, and show that a violation of
the equivalence principle does not occur when the measurement is made far from
the turning point of the classical trajectory. I conclude with some remarks
about the strong equivalence principle in quantum mechanics.Comment: 10 pages, 1 figure, research pape
Quantum fluctuations and life
There have been many claims that quantum mechanics plays a key role in the
origin and/or operation of biological organisms, beyond merely providing the
basis for the shapes and sizes of biological molecules and their chemical
affinities. These range from the suggestion by Schrodinger that quantum
fluctuations produce mutations, to the conjecture by Hameroff and Penrose that
quantum coherence in microtubules is linked to consciousness. I review some of
these claims in this paper, and discuss the serious problem of decoherence. I
advance some further conjectures about quantum information processing in
bio-systems. Some possible experiments are suggested.Comment: 10 pages, no figures, conference pape
Physics of the Pseudogap State: Spin-Charge Locking
The properties of the pseudogap phase above Tc of the high-Tc cuprate
superconductors are described by showing that the Anderson-Nambu SU(2) spinors
of an RVB spin gap 'lock' to those of the electron charge system because of the
resulting improvement of kinetic energy. This enormously extends the range of
the vortex liquid state in these materials. As a result it is not clear that
the spinons are ever truly deconfined. A heuristic description of the
electrodynamics of this pseudogap-vortex liquid state is proposed.Comment: Submitted to Phys Rev Letter
Unified Treatment of Quantum Fluctuation Theorem and Jarzynski Equality in Terms of microscopic reversibility
There are two related theorems which hold even in far from equilibrium,
namely fluctuation theorem and Jarzynski equality. Fluctuation theorem states
the existence of symmetry of fluctuation of entropy production, while Jarzynski
equality enables us to estimate the free energy change between two states by
using irreversible processes. On the other hand, relationship between these
theorems was investigated by Crooks for the classical stochastic systems. In
this letter, we derive quantum analogues of fluctuation theorem and Jarzynski
equality microscopic reversibility condition. In other words, the quantum
analogue of the work by Crooks is presented.Comment: 7pages, revised versio
- …