共查询到20条相似文献,搜索用时 46 毫秒
1.
We study the consequences of the KMS-condition on the properties of quasi-particles, assuming their existence. We establish
- If the correlation functions decay sufficiently, we can create them by quasi-free field operators.
- The outgoing and incoming quasi-free fields coincide, there is no scattering.
- There are may age-operatorsT conjugate toH. For special forms of the dispersion law ε(k) of the quasi-particles there is aT commuting with the number of quasi-particles and its time-monotonicity describes how the quasi-particles travel to infinity.
2.
G. Müller 《Zeitschrift für Physik B Condensed Matter》1987,68(2-3):149-159
The present study highlights some of the complexities observed in the dynamical properties of one-dimensional quantum spin systems. Exact results for zero-temperature dynamic correlation functions are presented for two contrasting situations:
- a system with a fully ordered ferromagnetic ground state;
- a system at aT c=0 critical point.
3.
J. Ginibre 《Communications in Mathematical Physics》1969,14(3):205-234
We prove that the following lattice systems:
- anisotropic Heisenberg model,
- Ising model with transverse magnetic field,
- quantum lattice gas with hard cores extending over nearest neighbours,
4.
Michael Henle 《Communications in Mathematical Physics》1970,19(4):273-275
Theorem. Let a topological groupG be represented (a→φ a ) by *-automorphisms of a von Neumann algebraR acting on a separable Hilbert spaceH. Suppose that
- G is locally compact and separable,
- R′ is properly infinite,
- for anyT∈R,x,y∈H the function
5.
Francesco Pegoraro 《Communications in Mathematical Physics》1975,42(1):41-63
We consider a theorem due to Michel [1] which relates the invariance properties in peculiar directions in a linear space on which we represent a Lie groupG to the extremal points of an arbitrary smoothG-invariant function. The group we are interested in isSO(4) and we apply the mathematical results to the following problems:
- mixed linear Stark Zeeman effect in a hydrogen atom,
- perturbation of a finite Robertson-Walker metric,
- gas evolutions preserving angular momentum and vorticity.
6.
Stefano Moretti 《Zeitschrift fur Physik C Particles and Fields》1997,73(4):653-667
The complete matrix element for e + e? → bb?W+ W? is computed at tree-level within the Minimal Supersymmetric Standard Model. Rates of interest to phenomenological analyses at the Next Linear Collider are given. In particular, we study:
- ? tt? production and decay tt? →(bW +)(b?W ?)
- ? ZH production followed by Z → bb? and H → W + W?
- ? AH production followed by A→ bb? and H → W + W?
- ? hW + W? production followed by h→ bb?.
7.
E. Boos I. Ginzburg K. Melnikov T. Sack S. Shichanin 《Zeitschrift fur Physik C Particles and Fields》1992,56(3):487-491
Three possibilities to observe the Higgs-top interation at future γγ-colliders are discussed:
- associated Higgs production via the \(\gamma \gamma \to t\bar tH\) reaction,
- Higgs obliged radiative correction to the \(\gamma \gamma \to t\bar t\) channel,
- Higgs resonance production via γγ→H→ZZ.
8.
E. Mourre 《Communications in Mathematical Physics》1981,78(3):391-408
We give a sufficient condition for a self-adjoint operator to have the following properties in a neighborhood of a pointE of its spectrum:
- its point spectrum is finite;
- its singular continuous spectrum is empty;
- its resolvent satisfies a class of a priori estimates.
9.
V. Yu. Klepikov 《Radiophysics and Quantum Electronics》1996,39(10):857-861
Analyzing statistically the magnetic and Doppler velocity data for 85 quiescent prominences observed in 1983–1987 by Nikolsky's magnetograph, we came to the following preliminary conclusions: The average longitudinal magnetic field of the prominence determines the dynamic velocity of the latter: the stronger magnetic fields correspond to the higher Doppler velocities. A longitudinal magnetic field less than 25 G allows the material to move with arbitrary velocity within the limits of several kilometers per second. A magnetic field higher than 25 G suppresses such movements. The horizontal length of the flux tube exceeds its vertical part by 1.5 orders of magnitude (the upper limit). There is an angle of 10°between the horizontal component of the velocity vector in quiescent prominences and the long axis of the filament. The maximum velocity in quiescent prominences is about 7 km/s. 相似文献
10.
J. Halbritter 《Applied Physics A: Materials Science & Processing》1986,39(1):49-57
Broad-area electrodes show electron emission already at electric field strengthsF≈107 V/m. This enhanced field emission (EFE) occurs only for contaminated surfaces. EFE is accompanied by photon emission and gas desorption yielding finally discharges. EFE is caused by dust and contaminants initiating the following effects: an electron is stochastically emitted in a trigger zone the electron gains energyΔE?eΔxF * which excites electronic states which relax by the emission of electrons, photons, and atoms where the positive charges left behind enhanceF *=βF (β?1) initiating so an electron avalanche, i.e., a high conductivity channel. Because of charge migration and neutralization, this avalanche has a life time. This pulsating EFE is accompanied by light emission and gas desorption yielding finally a gas cloud and a discharge. The pulsating, self-sustained EFE has the same root as: the enhanced secondary emission found first by Malter the conductivity switching exhibited by thin (≈ 1 μm) layers of semiconductors or insulators the normal cathode fall and the firing-wave instability in neurodynamics. 相似文献
11.
J. C. M. Henning J. H. den Boef 《Applied Physics A: Materials Science & Processing》1978,16(4):353-357
A novel method for measuring magnetostriction constants is presented. A strain, periodic in time, applied to the sample, causes a modulation of the ferromagnetic resonance line position. The height of the signal obtained after phase-sensitive detection is proportional to the strain modulation depth. The appropriate magnetostriction constant λ is obtained by comparing the height of the SMFMR signal with that of the FMR line, as recorded by means of magnetic field modulation. Features of the new technique are:
- high sensitivity: λmin? 10?9 forM=100 Oe and linewidth ΔH d=1 Oe;
- λ's belonging to distinct precession modes are separately determined;
- applicable to thin layers for which strain gauge techniques cannot be used;
- wide temperature range: 1.2 K<T<300 K;
- uniform stress.
12.
Removal of a wide range of trace organic contaminants from water to concentrations below USEPA Maximum Contaminant Levels (MCL) remains an important goal for the water industry. Design of advanced carbon based adsorption systems represents a unique approach to solving these problems. A number of successful examples are cited in this paper and are briefly summarized in the following section.
- Removal of foulants such as humic acid using nanoparticle carbon blacks and chemically activated nanoporous fibers;
- Removal of trace organic contaminants such as benzene, toluene, ethylbenzene and p-xylene (BTEX) to levels below USEPA MCL using nanoporous carbon fibers;
- Removal of trace chemical warfare simulants such as diisopropylmethyl phosponate and chloroethylethylsulfide using enlarged nanoporous carbon fibers;
- Removal of trace chlorinated solvents such as trichloroethylene (TCE) and chloroform using tailored nanoporous carbon fibers;
- Removal of the trace herbicide, atrazine, to below USEPA MCL level using nanoporous chemically activated fibers.
13.
A. Jánosi 《Zeitschrift für Physik B Condensed Matter》1990,80(3):393-400
We study the effects of some of the most important and typical structural changes in two-phase systems on selected structural parameters obtained from small-angle x-ray scattering (SAXS) measurements. To limit the present study, it was assumed that the Phase, 1, embedded in the matrix
- is monodispersed and homogeneous,
- possesses one of the three most extreme shapes (spherical, fibrillar or lamellar) and
- changes its behaviour
- through type change (spinodal or nucleotic or coarsening), without changing the shape,
- through a change of the shape only, or
- through a) (type change) and b) (shape change) simultaneously.
- chord lengthl 1 (and/or radius of gyrationR),
- volume partw 1 of the Phase 1, and
- relative inner surfaceS v of the system.
- spinodal change, all three SAXRS parameters are increasing or decreasing simultaneously and proportional to a power of the intensity of the change,
- nucleotic change,l 1 (and/orR) is unchanged, the other two (w 1 andS v ) are increasing or decreasing simultaneously and directly proportional to the intensity,
- coarsening change,w 1 is unchanged and anincreasing ofl 1 is always accompanied by adecreasing ofS v and vice versa.
14.
Massimo Campanino Abel Klein J. Fernando Perez 《Communications in Mathematical Physics》1991,135(3):499-515
We study the zero-temperature behavior of the Ising model in the presence of a random transverse field. The Hamiltonian is given by $$H = - J\sum\limits_{\left\langle {x,y} \right\rangle } {\sigma _3 (x)\sigma _3 (y) - \sum\limits_x {h(x)\sigma _1 (x)} } $$ whereJ>0,x,y∈Z d, σ1, σ3 are the usual Pauli spin 1/2 matrices, andh={h(x),x∈Z d} are independent identically distributed random variables. We consider the ground state correlation function 〈σ3(x)σ3(y)〉 and prove:
- Letd be arbitrary. For anym>0 andJ sufficiently small we have, for almost every choice of the random transverse fieldh and everyx∈Z d, that $$\left\langle {\sigma _3 (x)\sigma _3 (y)} \right\rangle \leqq C_{x,h} e^{ - m\left| {x - y} \right|} $$ for ally∈Z d withC x h <∞.
- Letd≧2. IfJ is sufficiently large, then, for almost every choice of the random transverse fieldh, the model exhibits long range order, i.e., $$\mathop {\overline {\lim } }\limits_{\left| y \right| \to \infty } \left\langle {\sigma _3 (x)\sigma _3 (y)} \right\rangle > 0$$ for anyx∈Z d.
15.
Inequalities on eigenvalues of the Schrödinger operator are re-examined in the case of spherically symmetric potentials. In particular, we obtain:
- A connection between the moments of order (n ? 1)/2 of the eigenvalues of a one-dimensional problem and the total number of bound statesN n, inn space dimensions;
- optimal bounds on the total number of bound states below a given energy in one dimension;
- alower bound onN 2;
- a self-contained proof of the inequality for α ≧ 0,n ≧ 3, leading to the optimalC 04,C 3;
- solutions of non-linear variation equations which lead, forn ≧ 7, to counter examples to the conjecture thatC 0n is given either by the one-bound state case or by the classic limit; at the same time a conjecture on the nodal structure of the wave functions is disproved.
16.
In ferrites a large number of after-effects are found, with time constants between nano-seconds and years. In this review the after-effects due to ion-and electron motion will be treated. One finds:
- single-ion effects in combination with lattice deformations, e.g. Mn3+;
- ion effects caused by mobile vacancies, e.g. Co2+;
- effects due to electron transfer:
- Co2+?Co3+
- Me2+?Fe3+, in combination with Me4+ and vacancies.
- Me4+?Fe2+, with Me=Si, Ti (photomagnetic effect).
17.
T. P. Das 《Hyperfine Interactions》1979,6(1-4):53-62
The origin of ferromagnetism in the transition metal ferromagnets, iron, cobalt, and nickel is discussed, from an ab initio band structure point of view, with proper attention to the explicit roles of exchange, correlation and hybridization effects. The influence of these effects and all the mechanisms such as direct, exchange core polarization and many-body effects that have been found important for the hyperfine properties of atomic systems are included in attempting to understand the experimentally observed hyperfine fields at the nuclei in these metals. Spin-density distributions using calculated spin polarized band wave-functions are used to make comparisons with experimental neutron scattering data. The impact of the results of analyses of hyperfine fields at the nuclei and spin density distributions on the origin of hyperfine fields at muon sites is discussed. This talk, and the corresponding article for the proceedings of this conference, will deal with the theoretical understanding of the hyperfine fields at the nuclei and neutron scattering form factors in the three ferromagnetic metals, iron, cobalt and nickel and the impact of this understanding on that of the origin of the hyperfine fields at positive muon sites in these metals. With these aims in mind, the plan of my talk will be the following.
- Discussion of a first-principle principle procedure to obtain the energy bands and electronic wave-functions in these metals and the understanding of the origin of their ferromagnetism from a band point of view.
- Mechanisms contributing to hyperfine fields in atomic systems and their relevance for ferromagnetic metals.
- The mechanisms for the origin of hyperfine fields in these metals, corresponding theoretical results and comparison with experiment.
- Comparison between calculated spin-density distributions and experimental results from neutron scattering data.
- Remarks on the origin of hyperfine fields at muon sites in these metals.
18.
19.
Using the formfactors which are entire analytic functions in a momentum space, nonlocality is introduced for a wide class of interaction Lagrangians in the quantum theory of one-component scalar field φ(x). We point out a regularization procedure which possesses the following features:
- The regularizedS δ matrix is defined and there exists the limit $$\mathop {\lim }\limits_{\delta \to 0} S^\delta = S.$$
- The Green positive-frequency functions which determine the operation of multiplication in \(S \cdot S^ + \mathop = \limits_{Df} S \circledast S^ + \) can be also regularized ?δ and there exists the limit $$\mathop {\lim }\limits_{\delta \to 0} \circledast ^\delta = \circledast \equiv .$$
- The operator \(J(\delta _1 ,\delta _2 ,\delta _3 ) = S^{\delta _1 } \circledast ^{\delta _2 } S^{\delta _3 + } \) is continuous at the point δ1=δ2=δ3=0.
- $$S^\delta \circledast ^\delta S^{\delta + } \equiv 1at\delta > 0.$$ Consequently, theS-matrix is unitary, i.e. $$S \circledast S^ + = S \cdot S^ + = 1.$$
20.
It is demonstrated that a closed symmetric derivation δ of aC?-algebra \(\mathfrak{A}\) generates a strongly continuous one-parameter group of automorphisms of aC?-algebra \(\mathfrak{A}\) if and only if, it satisfies one of the following three conditions
- (αδ+1)(D(δ))= \(\mathfrak{A}\) , α∈?\{0}.
- δ possesses a dense set of analytic elements.
- δ possesses a dense set of geometric elements.
- ∥(αδ+1)(A)∥≧∥A∥, α∈IR,A∈D(δ).
- If α∈IR andA∈D(δ) then (αδ+1)(A)≧0 impliesA≧0.