共查询到20条相似文献,搜索用时 31 毫秒
1.
G. A. Kozlov 《Physics of Particles and Nuclei》2010,41(6):954-956
A field model for a quark and an antiquark binding is described. Quarks interact via a gauge unparticle (“ungluon”). The model
is formulated in terms of Lagrangian which features the source field S(x) which becomes a local pseudo-Goldstone field of conformal symmetry — the pseudodilaton mode and from which the gauge non-primary
unparticle field is derived by B
μ(x) ∼ ∂μ
S(x). Because the conformal sector is strongly coupled, the mode S(x) may be one of new states accessible at high energies. We have carried out an analysis of the important quantity that enters
in the “ungluon” exchange pattern — the “ungluon” propagator. 相似文献
2.
The aim of the present work is to show how, using the differential calculus associated to Dirichlet forms, it is possible
to construct non-trivial Fredholm modules on post critically finite fractals by regular harmonic structures (D, r). The modules are (d
S
, ∞)–summable, the summability exponent d
S
coinciding with the spectral dimension of the generalized Laplacian operator associated with (D, r). The characteristic tools of the noncommutative infinitesimal calculus allow to define a d
S
-energy functional which is shown to be a self-similar conformal invariant.
Thiswork has been supported by the project “Teoria ellittica e forme di Dirichlet su spazi frattali” G.N.A.M.P.A. 2008 and
by the G.R.E.F.I.-G.E.N.C.O. French-Italian Research Group. 相似文献
3.
Shaolin Liao Ronald J. Vernon 《International Journal of Infrared and Millimeter Waves》2007,28(6):479-490
The newly developed Taylor-Interpolation-FFT (TI-FFT) algorithm dramatically increases the computational speeds for millimeter
wave propagation from a planar (cylindrical) surface onto a “quasi-planar” (“quasi-cylindrical”) surface. Two different scenarios
are considered in this article: the planar TI-FFT is for the computation of the wave propagation from a plane onto a “quasi-planar” surface and the cylindrical TI-FFT is for the computation of wave propagation from a cylindrical surface onto a “quasi-cylindrical” surface. Due to the
use of the FFT, the TI-FFT algorithm has a computational complexity of O(N
2 log2
N
2) for an N × N computational grid, instead of N
4 for the direct integration method. The TI-FFT algorithm has a low sampling rate according to the Nyquist sampling theorem.
The algorithm has accuracy down to −80 dB and it works particularly well for narrow-band fields and “quasi-planar” (“quasi-cylindrical”)
surfaces. 相似文献
4.
A computational scheme based on the infinite order sudden approximation (IOS) is proposed for treating molecular and screening
effects in muonic atom scattering at low energies. With this scheme the differential (dσ/dΩ(ɛj← 0|θ) and the total σtot(ɛ) cross-sections of muonic atom scattering on molecules of hydrogen isotopes are calculated at energies ɛrot=ℏωI⩽ɛ⩽ɛvib= ℏω03BD;. The IOS permits a quantitative analysis of the dependence of the differential cross-sections on the scattering angle and
on the rotational excitations, particularly the rotational rainbow effects. An attractive feature of this approach is also
to include the energy and the angular dependencies in the “input” cross-sections describing the muonic atom scattering on
each bare nucleus of the molecule. The calculated total cross-sections ωtot(ɛ) are in agreement with the data obtained earlier with the pseudopotential approach.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
5.
A model for multiparticle production process in high-energy hadronic collisions is proposed. In the centre of mass (CM) system
of colliding particles the target and the projectile are assumed to pass through each other sharing energies allowed by kinematical
constraints. Thus in app collision the energy associated with each is √S/2 (S being the square of the CM energy) which is taken to be the real variable that governs the number of particles produced.
In the case of hadronnucleus collisions the projectile and the target ofv nucleons lying in a (Lorentz contracted) tube pass through each other sharing energies ⋍ √S
A2, whereS
A ⋍vS. Before the final state particles emerge from these systems, the constituents of the target, i.e.,v nucleons share equally (= √S
A2v) the total energy associated with the target and become the centres from which final state particles stem out. Several results
have been discussed. 相似文献
6.
A one parameter quantum deformationS
μ
L(2,ℂ) ofSL(2,ℂ) is introduced and investigated. An analog of the Iwasawa decomposition is proved. The compact part of this decomposition
coincides withS
μ
U(2), whereas the solvable part is identified as a Pontryagin dual ofS
μ
U(2). It shows thatS
μ
L(2,ℂ) is the result of the dual version of Drinfeld's double group construction applied toS
μ
U(2). The same construction applied to any compact quantum groupG
c
is discussed in detail. In particular the explicit formulae for the Haar measures on the Pontryagin dualG
d
ofG
c
and on the double groupG are given. We show that there exists remarkable 1-1 correspondence between representations ofG and bicovariant bimodules (“tensor bundles”) overG
c
. The theory of smooth representations ofS
μ
L(2,ℂ) is the same as that ofSL(2,ℂ) (Clebsh-Gordon coefficients are however modified). The corresponding “tame” bicovariant bimodules onS
μ
U(2) are classified. An application to 4D
+ differential calculus is presented. The nonsmooth case is also discussed. 相似文献
7.
8.
Scales in nuclear matter: Chiral dynamics with pion nucleon form factors<Superscript>⋆</Superscript>
N. Kaiser M. Mühlbauer W. Weise 《The European Physical Journal A - Hadrons and Nuclei》2007,31(1):53-60
A systematic calculation of nuclear matter is performed which includes the long-range correlations between nucleons arising
from one- and two-pion exchange. Three-body effects from 2π exchange with excitations of virtual Δ(1232)-isobars are also
taken into account in our diagrammatic calculation of the energy per particle ˉ(k
f). In order to eliminate possible high-momentum components from the interactions we introduce at each pion-baryon vertex a
form factor of monopole type. The empirical nuclear matter saturation point, ρ0 ≃ 0.16fm^-3, ˉ0 ≃ - 16MeV, is well reproduced with a monopole mass of Λ ≃ 4πf
π ≃ 1.16GeV. As in the recent approach based on the universal low-momentum NN potential V
low-k, the inclusion of three-body effects is crucial in order to achieve saturation of nuclear matter. We demonstrate that the
dependence of the pion exchange contributions to ˉ(k
f) on the “resolution” scale Λ can be compensated over a wide range of Λ by counterterms with two “running” contact couplings.
As a further application we study the in-medium chiral condensate 〈ˉq〉(ρ) beyond the linear density approximation. For ρ ⩽ 1.5ρ0 we find small corrections from the derivative dˉ(k
f)/dm
π, which are stable against variations of the monopole regulator mass Λ. 相似文献
9.
Dielectric relaxation measurements of formamide (FMD)-N,N-dimethylaminoethanol (DMAE) solvent mixtures have been carried out over the entire concentration range using time domain
reflectometry technique at 25, 35 and 45°C in the frequency range of 10 MHz to 20 GHz. The mixtures exhibit a principle dispersion
of the Davidson-Cole relaxation type at microwave frequencies. Bilinear calibration method is used to obtain complex permittivity
ɛ*(ω) from complex reflection coefficient ρ*(ω) over the frequency range of 10 MHz to 10 GHz. The excess permittivity (ɛ
E), excess inverse relaxation time (1/τ)E, Kirkwood correlation factor (g
eff), activation energy and Bruggeman factor (f
B) are also calculated to study the solute-solvent interaction.
相似文献
10.
Electrical conductivity and dielectric properties of single-crystal TlGaSe2 have been studied as a function of γ irradiation dose in the 100–280 K range including the existence of an incommensurate phase. Anomalies in the form of maxima
have been observed in the σ=f(T), tan δ=f(T), and ɛ=f(T) curves at the points of transition from the paraphase to incommensurate (IC) phase, T
i, and from the IC to commensurate phase, T
c. The increase in the quantities σ, tan δ, and ɛ observed initially with increasing irradiation dose is followed by their strong decrease and disappearance of the anomalies.
It has been established that γ irradiation does not affect the phase transition temperatures T
i and T
c.
Fiz. Tverd. Tela (St. Petersburg) 40, 1328–1331 (July 1998) 相似文献
11.
Sheleg A. U. Hurtavy V. G. Shautsova V. V. Aliev V. A. 《Physics of the Solid State》2012,54(3):622-625
This paper reports on a study of the dielectric permittivity and electrical conductivity of single-crystal TlInS
x
Se2 − x
solid solutions as functions of temperature and composition. It has been found that the dielectric permittivity ɛ and electrical
conductivity σ decrease with increasing x and increase with growing temperature. The temperature dependences ɛ = f(T) and σ = f(T) for TlInS
x
Se2 − x
crystals have been demonstrated to reveal anomalies in the form of maxima, which suggests that these crystals undergo phase
transitions. The temperatures of the phase transitions increase with increasing x. 相似文献
12.
Results of temperature and frequency dependent a.c. conductivity of pure and nickel-doped a-As2S3 are reported. The a.c. conductivity of pure As2S3 obeys a well-known relationship: σac ∝ω
s. Frequency exponents is found to decrease with increasing temperature. Correlated barrier hopping (CBH) model successfully explains the entire
behaviour of a.c. conductivity with respect to temperature and frequency for pure As2S3. But a different behaviour of a.c. conductivity has been observed for the nickel doped As2S3. At higher temperatures, distinct peaks have been observed in the plots of temperature dependence of a.c. conductivity. The
frequency dependent behaviour of a.c. conductivity (σac ∝ω
s) for nickeldoped As2S3 is similar to pure As2S3 at lower temperatures. But at higher temperatures, ln σac vs lnf curves have been found to deviate from linearity. Such a behaviour has been explained by assuming that nickel doping gives
rise to some neutral defect states (D
0′) in the band gap. Single polaron hopping is expected to occur between theseD
0‘ andD
+ states. Furthermore, allD
+,D
0′ pairs are assumed to be equivalent, having a fixed relaxation time at a given temperature. The contribution of this relaxation
to a.c. conductivity is found to be responsible for the observed peak in the plots of temperature dependence of a.c. conductivity
for nickel-doped As2S3. The entire behaviour of a.c. conductivity with respect to temperature and frequency has been explained by using CBH and
“simple pair” models. Theoretical results obtained by using these models, have been found to be in agreement with the experimental
results. 相似文献
13.
A. V. Ivanov Yu. E. Kalinin V. N. Nechaev A. V. Sitnikov 《Physics of the Solid State》2009,51(12):2474-2479
The concentration dependences of the electrical resistivity and complex permeability of [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
multilayer structures and (Co45Fe45Zr10)
x
(Al2O3)100 − x
composites have been studied. It has been established that introduction of a semiconductor interlayer into the (Co45Fe45Zr10)
x
(Al2O3)100 − x
composites substantially decreases the electrical resistivity of [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
multilayer structures. The concentration dependences of the real and imaginary parts of the complex permeability of the [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
nanomultilayer structures substantially differ from those of the (Co45Fe45Zr10)
x
(Al2O3)100 − x
composites. The real part of the complex permeability of the [“(Co45Fe45Zr10)
x
(Al2O3)100 − x
”/“α-Si: H”]
n
nanomultilayer structures follows the curve with a minimum near the percolation threshold of the composite, and the imaginary
part smoothly decreases as the ferromagnetic phase concentration increases. The results obtained are explained by the increase
in the bifurcation temperature due to the conduction electrons of the semiconductor interlayer, which favor magnetic ordering
of ferromagnetic grains. 相似文献
14.
A geometrization of classical mechanics is presented which may be considered as a realization of the Hertz picture of mechanics.
The trajectories in thef-dimensional configuration spaceV
f
of a classical mechanical system are obtained as the projections onV
f
of the geodesics in an (f + 1) dimensional Riemannian spaceV
f + 1, with an appropriate metric, if the additional (f + 1)th coordinate, taken to be an angle, is assumed to be “cyclic”.
When the additional (angular) coordinate is not cyclic we obtain what may be regarded as a generalization of classical mechanics
in a geometrized form. This defines new motions in the neighbourhood of the classical motions. It has been shown that, when
the angular coordinate is “quasi-cyclic”, these new motions can be used to describe events in the quantum domain with appropriate
periodicity conditions on the geodesics inV
f + 1. 相似文献
15.
A. Kh. Inoyatov L. L. Perevoshchikov A. Kovalík O. Dragoun D. V. Filosofov 《The European Physical Journal A - Hadrons and Nuclei》2011,47(7):84
The conversion electron spectrum of the 22.5keV M1 + E2 nuclear transition in 149Sm from the electron capture decay of 149Eu was experimentally studied for the “Eu2O3” and “EuF3” compounds in which 149Eu ions have the same assumed oxidation number +3 . While the energies of the L, M, N, O, and P1 conversion lines for “EuF3” were lower, on average, by 1.7(1), 2.7(2), 2.3(3), 4.1(2), and 5.7(9)eV, respectively, than those for “Eu2O3”, no changes between the two ligand complexes were observed for relative intensities of the conversion lines and their natural
widths within the error limits. 相似文献
16.
We consider the Couette flow between two plates. The lower plate is fixed and has periodically placed riblets of the characteristic
size ɛ on it. In the limit ɛ → 0 we find the effective Couette-Navier flow as an O(ɛ
2
) approximation for the effective mass flow and an O(ɛ
2
)L
1
-approximation for the velocity. In the effective solution the effect of roughness enters through the Navier slip condition
with the matrix coefficient in front of the effective shear stress, calculated using a boundary layer problem. Furthermore,
an O(ɛ
2
) approximation for the tangential drag force is found. In all estimates explicit dependence on the kinematic viscosity ν,
the velocity of the upper plate and the distance between the plates L
3
is kept. Also the uniqueness of the solution is expressed through a non-linear algebraic condition linking and L
3
. Then the result is applied to the viscous sub-layers around immersed bodies, strictly containing the surface riblets. It
is found that for the riblets of the characteristic size ɛ, being of the order smaller or equal to , the approximation obtained for the tangential drag could be applied. We compare ɛ and for realistic data and our results lead to the conclusion that the riblets reduce significantly tangential drag, which may
explain their presence on the skin of Nektons.
Received: 14 December 2001 / Accepted: 1 August 2002 Published online: 7 November 2002 相似文献
17.
Based on the Dyson-Schwinger Equations (DSEs) of QCD in the “rainbow” approximation, the fully dressed quark propagator S
f
(p) is investigated, and then an algebraic parametrization form of the propagator is obtained as a solution of the equations.
The dressed quark amplitudes A
f
and B
f
which built up the fully dressed quark propagator, and the dynamical running masses M
f
, which is defined by A
f
and B
f
for light quarks u, d and s, are calculated, respectively. Using the predicted current masses m
f
, quark local vacuum condensates, and our predicted value of pion decay constant, the masses of Goldstone bosons K, π and η and their in-medium values are also evaluated. Our predictions fit to data and to many other different calculations quite
well. The numerical results show that the mass of quark is dependent of its momentum p
2. The fully dressed quark amplitudes A
f
and B
f
have correct behaviors and can be used for many purposes in our future researches on non-perturbative QCD.
相似文献
18.
We find theoretically that competition between ∼K
f
q
4 and ∼Qq
2 terms in the Fourier-transformed conformational energy of a single-lipid chain, in combination with interchain entropic repulsion
in the hydrophobic part of the lipid (bi)layer, may cause a crossover on the bilayer pressure-area isotherm P(A)∼(A−A
0)−α. The crossover manifests itself in the transition from α = 5/3 to α = 3. Our microscopic model represents a single-lipid
molecule as a worm-like chain with a finite irreducible cross-section area A
0, a flexural rigidity K
f
, and a stretching modulus Q in a parabolic potential with the self-consistent curvature B(A) formed by entropic interactions between hydrocarbon chains in the lipid layer. The crossover area A* obeys the relation Q/√K
f
B(A*) ≈ 2. We predict a peculiar possibility of deducing the effective elastic moduli K
f
and Q of an individual hydrocarbon chain from the analysis of the isotherm with such a crossover. Also calculated is the crossover-related
behavior of the area compressibility modulus K
A
, the equilibrium area per lipid A
t
, and the chain order parameter S(θ).
The text was submitted by the authors in English. 相似文献
19.
F. Ricoul M. Dubois T. Zemb D. Plusquellec 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,4(3):333-340
By use of a mean-field approach the spin-wave dispersion of the Cu degrees of freedom in the undoped high-T C material Nd2CuO4is investigated. The experimentally observed sharp decrease of the Cu spin-wave gap with increasing temperature in the range
is explained by a paramagnetic-like susceptibility of the Nd spins which couple to the Cu subsystem. The degeneracy of the
“in-plane” and “out-of-plane” polarized Cu spin-wave branches is shown to be lifted by the uniaxial anisotropy of the Cu-Cu
nearest-neighbor interaction.
Received: 13 August 1997 / Revised: 4 December 1997 / Accepted: 11 December 1997 相似文献
20.
Nanoparticles of ɛ-Fe2.8Cr0.2N system exhibit the exchange bias phenomenon due to the exchange coupling of the spins of the antiferromagnetic (AF) oxide/oxynitride
surface layer and the ferromagnetic (FM) nitride core. Exchange bias is observed at 10 K both in the absence and presence
of cooling field. Due to the interface disorder, a mixture of parallel and anti-parallel/perpendicular coupling of the AF
and FM spins is observed. The roughness of AF-FM interface induces disorder due to the random exchange anisotropy. The saturation
magnetization is also found to be drastically lowered as compared to parent ɛ-Fe3N. Below 58 K, the broad peak (T
E
≅ T
f
) in zero-field cooled (ZFC) magnetization curves indicates the presence of unidirectional anisotropy and spinglass-like ordering,
that arises from the freezing of localized frustrated spins.
相似文献