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1.
Jump deformations and contractions of Lie algebras are inverse concepts, but the approaches to their computations are quite
different. In this paper, we contrast the two approaches, showing how to compute the jump deformations from the miniversal
deformation of a Lie algebra, and thus arrive at the contractions. We also compute contractions directly. We use the moduli
spaces of real 3-dimensional and complex 3 and 4-dimensional Lie algebras as models for explaining a deformation theory approach
to computation of contractions.
The research of the authors was partially supported by grants from the Mathematisches Forschungsinstitut Oberwolfach, OTKA
T043641, T043034 and the University of Wisconsin-Eau Claire. 相似文献
2.
L. -S. Young 《Communications in Mathematical Physics》1992,146(1):123-138
We prove exponential decay of correlations for (f, ), wheref belongs in a positive measure set of quadratic maps of the interval and is its absolutely continuous invariant measure. These results generalize to other interval maps.The results in this paper are announced in the Tagungsbericht of Oberwolfach, June 1990The author is partially supported by NSF 相似文献
3.
A. K. Vershovskii M. V. Balabas A. É. Ivanov V. N. Kulyasov A. S. Pazgalev E. B. Aleksandrov 《Technical Physics》2006,51(1):112-117
A new fast three-component variometer-magnetometer based on a cesium sensor is developed and tested. The device is intended
for measuring the longitudinal component of the geomagnetic field in the range from 20 to 65 μT and two transverse components
in the range ±1 μT. The reproducibility of measurements is ±0.15 nT, and the noise-limited sensitivity is 0.01 nT (in terms
of the rms deviation) or 0.04˝ for a measurement time of 0.1 s. 相似文献
4.
A correlation between the parameter β2 and a half-life T1/2 for oblate nuclei with sign β2 < 0 and an anticorrelation for elongated nuclei sign β2 > 0 are found. These analytical expressions for the function β2(T1/2) make it possible to calculate the shape parameters of β2 nuclei if we know the half-lives T1/2 for exotic nuclei for which this value is most accurately measured. 相似文献
5.
Andrej Košmrlj 《Journal of statistical physics》2011,142(6):1277-1286
T cells orchestrate adaptive immune responses by recognizing short peptides derived from pathogens, and by distinguishing
them from self-peptides. To ensure the latter, immature T cells (thymocytes) diffuse within the thymus gland, where they encounter
an ensemble of self-peptides presented on (immobile) antigen presenting cells. Potentially autoimmune T cells are eliminated
if the thymocyte binds sufficiently strongly with any such antigen presenting cell. We model thymic selection of T cells as
a random walker diffusing in a field of immobile traps that intermittently turn “on” and “off”. The escape probability of
potentially autoimmune T cells is equivalent to the survival probability of such a random walker. In this paper we describe
the survival probability of a random walker on a d-dimensional cubic lattice with randomly placed immobile intermittent traps, and relate it to the result of a well-studied
problem where traps are always “on”. Additionally, when switching between the trap states is slow, we find a peculiar caging
effect for the survival probability. 相似文献
6.
V. P.S. Awana A. Vajpayee M. Mudgel V. Ganesan A. M. Awasthi G. L. Bhalla H. Kishan 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):281-294
We report synthesis, structure/micro-structure, resistivity under magnetic
field [ρ(T)H], Raman spectra, thermoelectric power S(T), thermal conductivity
κ(T), and magnetization of ambient pressure argon annealed
polycrystalline bulk samples of MgB2, processed under identical
conditions. The compound crystallizes in hexagonal structure with space
group P6/mmm. Transmission electron microscopy (TEM) reveals electron micrographs
showing various types of defect features along with the presence of 3–4 nm
thick amorphous layers forming the grain boundaries of otherwise crystalline
MgB2. Raman spectra of the compound at room temperature exhibited
characteristic phonon peak at 600 cm-1. Superconductivity is observed
at 37.2 K by magnetic susceptibility χ(T), resistivity ρ(T), thermoelectric power
S(T), and thermal conductivity κ(T) measurements. The power law fitting
of ρ(T) give rise to Debye temperature (ΘD) at 1400 K which is
found consistent with the theoretical fitting of S(T), exhibiting Θ
D of 1410 K and carrier density of 3.81 × 1028/m3. Thermal
conductivity κ(T) shows a jump at 38 K, i.e., at Tc, which was
missing in some earlier reports. Critical current density (Jc) of up to
105 A/cm2 in 1–2 T (Tesla) fields at temperatures (T) of up to 10 K
is seen from magnetization measurements. The irreversibility field, defined
as the field related to merging of M(H) loops is found to be 78, 68 and 42 kOe
at 4, 10 and 20 K respectively. The superconducting performance parameters
viz. irreversibility field (Hirr) and critical current density
Jc(H) of the studied MgB2 are improved profoundly with addition of
nano-SiC and nano-diamond. The physical property parameters measured for
polycrystalline MgB2 are compared with earlier reports and a
consolidated insight of various physical properties is presented. 相似文献
7.
Marco Tizzano Gennady Dvoryanchikov Jennell K Barrows Soochong Kim Nirupa Chaudhari Thomas E Finger 《BMC neuroscience》2008,9(1):110
Background
"Type II"/Receptor cells express G protein-coupled receptors (GPCRs) for sweet, umami (T1Rs and mGluRs) or bitter (T2Rs), as well as the proteins for downstream signalling cascades. Transduction downstream of T1Rs and T2Rs relies on G-protein and PLCβ2-mediated release of stored Ca2+. Whereas Gαgus (gustducin) couples to the T2R (bitter) receptors, which Gα-subunit couples to the sweet (T1R2 + T1R3) receptor is presently not known. We utilized RT-PCR, immunocytochemistry and single-cell gene expression profiling to examine the expression of the Gαq family (q, 11, 14) in mouse taste buds. 相似文献8.
The thermo-emf ΔV and thermoelectric current ΔI generated by imposing a temperature gradient alternating at a period of T on a thermoelectric (TE) generator were measured as a function of t, where t is the lapsed time and 1/T was varied from 0 to 1/30 s-1. A TE generator was sandwiched between two Peltier modules connected in series. The alternating temperature gradients were produced by imposing an alternating voltage V on two Peltier modules, where V was varied from 1.0 to 3.7 V. Both ΔV and ΔI generated by the TE generator oscillate at a period of T but their amplitudes tend to increase monotonically with an increase of V. The effective thermo-emf ΔVeff and current ΔIeff calculated from ΔV and ΔI increase abruptly with an increase of 1/T and have a local maximum at 1/T=1/120 or 1/240 s-1. The generating power ΔWeff(=ΔVeffΔIeff) tends to increase proportionally with an increase of input power Winput, owing to the increase in the temperature difference. The rate of ΔWeff to Winput at 1/T=1/240 s-1 reached approximately 3.2 times as large as that obtained for the steady temperature gradient corresponding to 1/T=0 s-1. It was thus found that the generating power of the TE generator operating under the temperature gradient alternating at an optimum period is remarkably increased compared to that of a TE generator working under a conventional steady temperature gradient. PACS 72.15.Jf; 84.60.Rb; 85.30De 相似文献
9.
The structural phase transition from orthorhombic (T) phase to tetragonal (T′) phase in substituted La2−x
R
x
CuO4 (R = Pr, Nd, Sm, Eu and Gd) and T′ to T-phase in Pr2−x
M
x
CuO4−y
(M = Sr, Ca) has been studied by X-ray diffraction technique. The T-phase of La2CuO4 is transferred to T′ phase abruptly atx=0.8, 0.4, 0.4, 0.3 and 0.4 respectively for substitution of Pr, Nd, Sm, Eu and Gd for La in La2CuO4 without evidence of the T* phase. The T′ structure of Pr2CuO4 (x = 0.0) gets transformed to the T* structure at 30% Ca doping (x=0.6) and then to the T structure at 50% Ca doping (x=1.0), while for Sr-contentx=0.0, 0.4 and 1.0 it shows T′, T* and T structure respectively. 相似文献
10.
M. N. Khlopkin 《JETP Letters》1999,69(1):26-30
The specific heat of a V3Si single crystal (T
c=17 K, H
c2=20 T) in magnetic fields up to 8 T isinvestigated experimentally for three orientations of the field relative to the crystallographic
directions — H∥〈001〉, H∥〈110〉, and H∥〈111〉. Both the upper critical magnetic field and the specific heat of the mixed state are observed to depend on the orientation
of the magnetic field relative to the crystallographic directions (anisotropy): The critical field reaches its maximum value
and the specific heat its minimum value in a field along the 〈001〉 direction. The anisotropy scale in both phenomena increases
as the magnetic field and reaches 3% in a 6 T field. The interrelationship of the upper critical field anisotropy and the
specific-heat anisotropy in type-II superconductors is studied. It is shown that the anisotropy of the specific heat in the
mixed state in weak fields can serve as a criterion for nontrivial pairing.
Pis’ma Zh. éksp. Teor. Fiz. 69, No. 1, 26–29 (10 January 1999) 相似文献
11.
Anomalous behavior of the interlayer resistance of a BSCCO-2212 crystal in a parallel magnetic field
V. N. Zavaritskii 《JETP Letters》1996,63(2):139-145
The electrical resistance across the Cu-O layers of a BSCCO-2212 single crystal is investigated in the range of angles 0°⩽φ⩽90°
between the magnetic field H⩽15 T and the ab plane. It is found that the temperature dependence R(T) at the transition into the mixed state is much sharper for φ≃0° than for 1°≲φ≲90°, where R is determined by the perpendicular component of the magnetic field and is described by the Arrhenius law R∼exp(−U/T). For H∥ ab hysteretic jumps in R(T, H), which vanish as the current increases, are observed at fields in the range 5.5⩽H⩽11 T. This effect can be attributed to
a commensurate phase transition in a lattice of Josephson vortices.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 123–128 (25 January 1996) 相似文献
12.
Magnetic field effects (MFEs) on a photoinduced electron-transfer reaction in a semi-rigid linked system (RuP–C60) were examined in toluene and o-dichlorobenzene. The transient absorption spectra indicated that the photogenerated biradical produced by an intramolecular
electron-transfer reaction was observed only in o-dichlorobenzene. The decay rate constants (k
d) for the biradical decreased steeply at lower magnetic fields (≤0.06 T) and rapidly recovered at 0.08 T. The k
d value was observed to decrease gradually above 0.2 T. The MFEs strongly indicated the formation of the singlet-born biradical
for RuP–C60. The dip in the MFE at 0.06 T was ascribed to the S–T level crossing mechanism. The MFEs above 0.2 T can be explained by
a spin–spin relaxation mechanism due to the anisotropic Zeeman interaction being related to the exchange interaction. 相似文献
13.
Magnetic properties of single crystal Ba2Cu3O4Cl2 with Cu3O4 planes were investigated by temperature‐ and magnetic‐field‐dependent anisotropic magnetization M(T,H) and zero‐field‐μSR.
Muon spin precession was observed below as well as above T=32 K where an anomaly in M(T) appears. At this temperature the
frequency of the precession changes and the damping of it diverges. This is an evidence for a magnetic transition. We also
found the temperature dependence of the H‐linear component of M(H) shows a maximum around T=80 K, which is similar to the
behavior of low‐dimensional magnets with an antiferromagnetic interaction.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
14.
The hyperfine field of substitutional and defect-associated In atoms in Ni has been determined by observing the radiative
destruction of β-asymmetry in the decay of114In. It is argued that the associated defect is a cubic vacancy cluster. The hyperfine fields were determined as −3.30(1) T
for substitutional In atoms, and +5.12(2) T for the defect associated atoms. 相似文献
15.
S.Z. Kalantari 《Hyperfine Interactions》2000,128(4):481-493
In this paper, we solve numerically kinetic equations for the chain reactions of μCF in triple H/D/T mixture. Regarding the
computational results, we show that μCF efficiency decreases by adding hydrogen H to D/T mixture. This is in contradiction
to the usual belief which expects the increase of μCF efficiency in H/D/T mixture. Our results are confirmed by the first
and recent experiment on μdt cycling rate in the triple mixture.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
16.
Hiroshi Yasuoka 《Hyperfine Interactions》1997,105(1-4):27-34
From the temperature dependence of the 63Cu nuclear spin‐lattice relaxation rate, 1/T1T, in the planar Cu(2) sites, it is now well established that a highly enhanced and strongly temperature dependent relaxation
process due to antiferromagnetic Cu spin fluctuations exists in all of the high‐Tc’s. The data also exhibit the opening of a gap in the low‐lying magnetic excitations with an energy comparable to the superconducting
gap, particularly for the so‐called low doping regime. It is also found that, irrespective of the system, the temperature
at which the spin‐gap opens, Tsg, determined as the peak of 1/T1T vs. T, has a linear decrease with increasing of the doping concentration. A spin‐gap phase diagram is proposed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
17.
G. Chardin 《Hyperfine Interactions》1997,109(1-4):83-94
We present arguments showing that it is natural to interpret the negative mass part of the Kerr solution as representing the
geometry experienced by antimatter. The C, P and T discrete transformations are considered for this geometry. The C and T
properties of the proposed identification are found to be in agreement with the usual representation of antimatter. In addition,
we conjecture a property of perfect stigmatism through Kerr wormholes which allows General Relativity to mimic antigravity.
Kerr wormholes would then act as “supermirrors” reversing the C, P and T images of an object seen through it. This interpretation
is subject to several experimental tests and able to provide an explanation, without any free parameter, of the “CP” violation
observed in the neutral kaon system.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
18.
U. Köbler A. Hoser 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(2):151-159
The basic issues of renormalization group (RG) theory, i.e. universality, crossover phenomena, relevant interactions etc.
are verified experimentally on magnetic materials. Universality is demonstrated on account of the saturation of the magnetic
order parameter for T ↦ 0. Universal means that the deviations with respect to saturation at T = 0 can perfectly be described
by a power function of absolute temperature with an exponent ε that is independent of spin structure and lattice symmetry.
Normally the Tε function holds up to ~0.85Tc where crossover to the critical power function occurs.
Universality for T ↦ 0 cannot be explained on the basis of the material specific magnon dispersions that are due to atomistic
symmetry. Instead, continuous dynamic symmetry has to be assumed. The quasi particles of the continuous symmetry can be described
by plane waves and have linear dispersion in all solids. This then explains universality. However, those quasi particles cannot
be observed using inelastic neutron scattering. The principle of relevance is demonstrated using the competition between crystal
field interaction and exchange interaction as an example. If the ratio of crystal field interaction to exchange interaction
is below some threshold value the local crystal field is not relevant under the continuous symmetry of the ordered state and
the saturation moment of the free ion is observed for T ↦ 0. Crossover phenomena either between different exponents or between
discrete changes of the pre-factor of the Tε function are demonstrated for the spontaneous magnetization and for the heat capacity. 相似文献
19.
Yu.P. Averin D.V. Balin V.R. Bom A.M. Demin D.L. Demin A.E. Drebushko V.P. Dzhelepov C.W.E. van Eijk V.V. Filchenkov A.N. Golubkov N.N. Grafov V.G. Grebinnik S.K. Grishechkin V.G. Klevtsov A.D. Konin A.A. Kukolkin S.V. Medved' A.B. Modenov V.A. Nazarov V.I. Pryanichnikov V.Ia. Rozhkov A.I. Rudenko S.M. Sadetsky G.G. Semenchuk V.T. Sidorov Yu.V. Smirenin I.I. Sukhoi V.V. Travkin N.I. Voropaev A.A. Yukhimchuk V.G. Zinov S.V. Zlatoustovskii 《Hyperfine Interactions》1999,118(1-4):121-125
Muon catalyzed fusion in a dense triple mixture of hydrogen isotopes was investigated for the first time. The experimental
method is based on the registration of neutrons from dtμ fusion by a full absorption detector in 4π geometry. The measurements were performed in H/D/T mixture at T=21 K and φ≃ 1.1 LHD using four sets of isotope concentrations. The basic parameters of the dtμ cycle (neutron yield, cycling rate and total sticking) in H/D/T mixtures obtained from neutron time distributions are presented
and discussed.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
The thermodynamic properties of a cluster of point Coulomb charges on a sphere have been analyzed using the Monte Carlo method
for the number of charges 20 ≤ N ≤ 90. The ground state of the system of charges is described in the model of a closed quasi-two-dimensional triangular lattice
with topological defects. We have determined the dependence of the Lindeman parameter δL of this system on N and on the dimensionless parameter $
\tilde T
$
\tilde T
, which is proportional to the temperature T and to the radius R of the cluster: $
\tilde T = {{k_B T\varepsilon R} \mathord{\left/
{\vphantom {{k_B T\varepsilon R} {e^2 }}} \right.
\kern-\nulldelimiterspace} {e^2 }}
$
\tilde T = {{k_B T\varepsilon R} \mathord{\left/
{\vphantom {{k_B T\varepsilon R} {e^2 }}} \right.
\kern-\nulldelimiterspace} {e^2 }}
, where ∈ is the dielectric constant of the medium and e is the charge of a particle. The “magic numbers,” i.e., the N values, for which the melting point of the closed triangular lattice of charges is much higher than those for neighboring
N values, have been found. The evolution of the lattice-melting mechanisms with an increase in the number of charges N in a mesoscopic cluster has been analyzed. For N ≤ 32, the melting of the lattice does not involve dislocations (nontopological melting); this behavior of the mesoscopic
system of charges on the sphere differs from the behavior of the extended planar two-dimensional system. At N ≳ 50, melting is accompanied by the formation of dislocations. The mechanism of dislocation-free non-topological melting
of a closed lattice, which occurs at small N values and is associated with the cooperative rotational motion of “rings” of particles, has been analyzed. The model has
various implementations in the mesoscopic region; in particular, it describes the system of electrons over the liquid-helium
cluster, the liquid-helium cluster with incorporated charged particles, a multielectron bubble in liquid helium, a charged
quantum dot, etc. 相似文献