8,111 research outputs found
Quantum Scattering Theory in the light of an exactly solvable model with rearrangement collisions
We present an exactly solvable quantum field theory which allows
rearrangement collisions. We solve the model in the relevant sectors and
demonstrate the orthonormality and completeness of the solutions, and construct
the S-matrix. In the light of the exact solutions constructed, we discuss
various issues and assumptions in quantum scattering theory, including the
isometry of the M\"oller wave matrix, the normalization and completeness of
asymptotic states, and the non-orthogonality of basis states. We show that
these common assertions do not obtain in this model. We suggest a general
formalism for scattering theory which overcomes these, and other, shortcomings
and limitations of the existing formalisms in the literature.Comment: 74 pages, uuencoded postscript fil
Proposal for an Experiment to Test a Theory of High Temperature Superconductors
A theory for the phenomena observed in Copper-Oxide based high temperature
superconducting materials derives an elusive time-reversal and rotational
symmetry breaking order parameter for the observed pseudogap phase ending at a
quantum-critical point near the composition for the highest . An
experiment is proposed to observe such a symmetry breaking. It is shown that
Angle-resolved Photoemission yields a current density which is different for
left and right circularly polarized photons. The magnitude of the effect and
its momentum dependence is estimated. Barring the presence of domains of the
predicted phase an asymmetry of about 0.1 is predicted at low temperatures in
moderately underdoped samples.Comment: latex, 2 figure
Phosphorus-containing imide resins
Bis- and tris-imides derived from tris (m-aminophenyl) phosphine oxides by reaction with maleic anhydride or its derivatives, and addition polymers of such imides, including a variant in which a mono-imide is condensed with a dianhydride and the product is treated with a further quantity of maleic anhydride. Such monomers or their oligomes may be used to impregnate fibers and fabrics which when cured, are flame resistant. Also an improved method of producing tris (m-aminophenyl) phosphine oxides from the nitro analogues by reduction with hydrazine hydrate using palladized charcoal or Raney nickel as the catalyst is described
Elastomer-modified phosphorus-containing imide resins
Phosphine oxide-containing polyimide resins modified by elastomers, are disclosed which have improved mechanical properties. These products are particularly useful in the production of fiber or fabric-reinforced composites or laminates
Phosphorus-containing imide resins
Cured polymers of bis and tris-imides derived from tris(m-aminophenyl) phosphine oxides by reaction with maleic anhydride or its derivatives, and addition polymers of such imides, including a variant in which a monoimide is condensed with a dianhydride and the product is treated with a further quantity of maleic anhydride prior to curing are disclosed and claimed. Such polymers are flame resistant. Also disclosed are an improved method of producing tris(m-aminophenyl) phosphine oxides from the nitro analogues by reduction with hydrazine hydrate using palladized charcoal or Raney nickel as the catalyst and fiber reinforced cured resin composites
The Influence of Quantum Critical Fluctuations of Circulating Current Order Parameters on the Normal State Properties of Cuprates
We study a model of the quantum critical point of cuprates associated with
the "circulating current" order parameter proposed by Varma. An effective
action of the order parameter in the quantum disordered phase is derived using
functional integral method, and the physical properties of the normal state are
studied based on the action. The results derived within the ladder
approximation indicate that the system is like Fermi liquid near the quantum
critical point and in disordered regime up to minor corrections. This implies
that the suggested marginal Fermi liquid behavior induced by the circulating
current fluctuations will come in from beyond the ladder diagrams.Comment: 7pages, 1 figure included in RevTex file. To appear in Phys. Rev.
Phosphorus-containing bisimide resins
The production of fire-resistant resins particularly useful for making laminates with inorganic fibers such as graphite fibers is discussed. The resins are by (1) condensation of an ethylenically unsaturated cyclic anhydride with a bis(diaminophenyl) phosphine oxide, and (2) by addition polymerization of the bisimide so obtained. Up to about 50%, on a molar basis, of benzophenonetetracarboxylic acid anhydride can be substituted for some of the cyclic anhydride to alter the properties of the products. Graphite cloth laminates made with these resins show 800 C char yields greater than 70% by weight in nitrogen. Limiting oxygen indexes of more than 100% are determined for these resins
Collective Modes in the Loop Current Ordered Phase of Cuprates
Recently two branches of weakly dispersive collective modes have been
discovered in under-doped cuprates by inelastic neutron scattering.
Polarization analysis reveals that the modes are magnetic excitations. They are
only visible for temperatures below the transition temperature to a broken
symmetry phase which was discovered earlier and their intensity increases as
temperature is further decreased. The broken symmetry phase itself has
symmetries consistent with ordering of orbital current loops within a unit-cell
without breaking translational symmetry. In order to calculate the collective
modes of such a state we add quantum terms to the Ashkin-Teller (AT) model with
which the classical loop current order has been described. We derive that the
mean field ground state of the quantum model is a product over all unit-cells
of linear combination of the four possible classical configurations of the loop
current order in each unit-cell. The collective modes are calculated by using a
generalized Holstein-Primakoff boson representation of orbital moment operators
and lead to three branches of gapped weakly dispersive collective modes. The
experimental results are consistent with the two lower energy branches; the
third mode is at a higher energy than looked for by present neutron scattering
experiments and might also be over-damped. Implications of the discovery of the
collective modes are discussed.Comment: 16 pages, 6 figure
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