共查询到20条相似文献,搜索用时 15 毫秒
1.
We argue that the existence of a new narrow (Γ ≤ 25 MeV) nucleon resonance N* (1685) is strongly supported by recent data
on the η photoproduction off the nucleon. The resonance has a much stronger photocoupling to the neutron than to the proton.
This nucleon resonance is a good candidate for the nonstrange member of the exotic antidecouplet of baryons—the partner of
the pentaquark Θ+. All of the properties of new N* (1685) known to date are summarized.
The text was submitted by the authors in English. 相似文献
2.
Tadayoshi Adachi 《Communications in Mathematical Physics》2007,275(2):443-477
We show the asymptotic completeness for N-body quantum systems with long-range interactions in a time-periodic electric field whose mean in time is non-zero, where
N ≥ 2. One of the main ingredients of this paper is to give some propagation estimates for physical propagators generated by
time-periodic Hamiltonians which govern the systems under consideration.
Research partially supported by the Grant-in-Aid for Young Scientists of MEXT #17740078. 相似文献
3.
Studying the ω<Emphasis Type="Italic">N</Emphasis> elastic and inelastic cross section with nucleons
Ye.S. Golubeva W. Cassing L.A. Kondratyuk A. Sibirtsev M. Büscher 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):271-277
We explore the possibility to measure the elastic and inelastic ωN cross section in p+d→d+ω+p
sp and p+A reactions. Our studies indicate that the elastic scattering cross sections can be determined for ω momenta above 1 GeV/c
in p+d reactions by gating on high proton spectator momenta whereas the ωN absorption cross section down to low relative ω momenta is most effectively studied in p+A reactions at beam energies 2.0–2.7 GeV.
Received: 15 October 1999 相似文献
4.
In this paper we study the supersymmetrization of the N = 1 and N = 2 nonlocal gas equation. We show that this system is bi-Hamiltonian. While the N = 1 supersymmetrization allows the hierarchy of equations to be extended to negative orders (local equations), we argue that
this is not the case for the N = 2 supersymmetrization. In the bosonic limit, however, the N = 2 system of equations lead to a new coupled integrable system of equations.
Presented at the International Colloquium “Integrable Systems and Quantum Symmetries”, Prague, 16–18 June 2005. 相似文献
5.
The Re-Analysis of the 1700 MeV Structure of the P
11 Partial Wave Using the πN → KΛ Production Data
We have used the Breit-Wigner resonance model with S
11, P
11, and P
13 resonances in the s-channel to reanalyze the old πN → KΛ data with the aim to establish the origin of the prominent structure in the total cross section in the vicinity of 1700 MeV.
We have found a new set of resonance parameters enforcing the experimentally observed structure of the total cross-section
data simultaneously with the linear dependence of the differential cross sections with cos θ in the energy range 1650 MeV
< W < 1800 MeV. Owing to the differential cross-section linearity, the P
13 partial wave has been strongly attenuated in this model, and the total cross-section structure is attributed to the resonant
behavior of the P
11 partial wave. In this paper we show that, at least in the Breit-Wigner resonance model, it is not possible to achieve a detailed
reproduction of the narrow 1700 MeV total cross-section peak using the standard partial widths. To understand the phenomenon,
a much narrower width of a resonant state, the N(1710) P
11 in our case, is required (Γ ≈ 68 MeV), but then the agreement of the model predictions with the total cross-section data
at higher energies is lost. One way out is to allow for the existence of another P
11 resonance in that energy range. The same feature is shown by the polarization data: The introduction of a much narrower resonance
spoils the level of agreement which the Breit-Wigner resonance model is able to achieve with experiment, but the consistency
is restored when another resonance is introduced. Analyzing the qqq or qqqq
nature of the recommended narrow P
11 structure in the neighborhood of 1700 MeV we reopen (remind of) the possibility that another P
11 resonant state exists in addition to the standard N(1710) P
11 PDG-resonance, and that one of the two states can be identified with the yet undiscovered cryptoexotic pentaquark state.
To clarify the situation, we strongly recommend a remeasurement of the πN → KΛ process in the energy range 1650 MeV < W < 1800 MeV. 相似文献
6.
I. N. Boboshin V. V. Varlamov B. S. Ishkhanov E. A. Romanovsky 《Physics of Atomic Nuclei》2007,70(8):1363-1368
New information about energies and occupation probabilities of neutron and proton single-particle (hole) subshells in even—even
nuclei was obtained in previous studies applying the method of putting into correspondence all available data on one-nucleon
pickup and stripping reactions. The most important and interesting resultwas identification of several nuclei as new magic
ones. Namely, itwas found that a filling of the neutron 2d
5/2 subshell in 96Zr makes this nuclide a magic one. Moreover, changes in proton subshell energies with increasing neutron number N are accompanied by an increasing energy gap between closed 2p
1/2 and empty 1g
9/2 subshells. Thus, the neutron number N = 56 appears to be a magic one if the proton number Z is equal to 40. The proton number Z = 40 manifests properties of the magic number in 96Zr. Therefore, 96Zr was identified as a new double-magic nucleus. Further investigations revealed that the energy of the first 2+ state E(2
1
+
) in 96Zr is much higher than that in the neighboring isotopes and isotones, whereas the ratio E(4
1
+
)/E(2
1
+
) and the quadrupole deformation parameter β2 are, vice versa, clearly lower. Moreover, the A dependence of the neutron separation energy B(n) in Zr isotopes has an irregularity at N = 56 which is typical of magic nuclei. As a result of these investigations, it was found that, near the Fermi energy, there
are two closed subshells with the same (and large) angular momentum j = 5/2 (viz. π1f
5/2 and ν2d
5/2). We call this situation the jj connection. The magic numbers under discussion (Z = 40 and N = 56) are achieved at the points where both subshells are closed, and in addition, the closed subshell with j = 1/2, π2p
1/2, occurs above the proton π1f
5/2 subshell. This looks like a result of some additional attractive proton-neutron interaction. It was found that application
of this scheme (jj connection) to other subshells reveals several other new magic nuclei: 54Ca (closed π1d
3/2 and ν2p
3/2 together with closed ν2p
1/2), 30S and 30Si (closed π1d
5/2 and ν1d
5/2 together with closed (π/ν)2s
1/2), and 14O and 14C (closed π1p
3/2 and ν1p
3/2 together with closed ν2p
1/2).
The text was submitted by the authors in English. 相似文献
7.
We compute the moments of the characteristic polynomials of random orthogonal and symplectic matrices, defined by averages
with respect to Haar measure on SO(2N) and USp(2N), to leading order as N → ∞, on the unit circle as functions of the angle θ measured from one of the two symmetry points in the eigenvalue spectrum . Our results extend previous formulae that relate just to the symmetry points, i.e. to θ = 0. Local spectral statistics are expected to converge to those of random unitary matrices in the limit as N → ∞ when θ is fixed, and to show a transition from the orthogonal or symplectic to the unitary forms on the scale of the mean eigenvalue
spacing: if θ = π
y/N they become functions of y in the limit when N → ∞. We verify that this is true for the spectral two-point correlation function, but show that it is not true for the moments
of the characteristic polynomials, for which the leading order asymptotic approximation is a function of θ rather than y. Symmetry points therefore influence the moments asymptotically far away on the scale of the mean eigenvalue spacing. We
also investigate the moments of the logarithms of the characteristic polynomials in the same context. The moments of the characteristic
polynomials of random matrices are conjectured to be related to the moments of families of L-functions. Previously, moments at the symmetry point θ = 0 have been related to the moments of families of L-functions evaluated at the centre of the critical strip. Our results motivate general conjectures for the moments of orthogonal
and symplectic families of L-functions evaluated at a fixed height t up the critical line. These conjectures suggest that the symmetry of the non-trivial zeros of the L-functions influences the moments asymptotically far, on the scale of the mean zero spacing, from the centre of the critical
strip. We verify that the second moments of real quadratic Dirichlet L-functions and a family of automorphic L-functions are consistent with our conjectures.
JPK is supported by an EPSRC Senior Research Fellowship.
BEO was supported by an Overseas Research Scholarship and a University of Bristol Research Scholarship. 相似文献
8.
We have studied spectral and amplitude-time characteristics of the emission by nitrogen, air, and the N2-CH4 mixture upon excitation by nanosecond and microsecond high-voltage discharge pulses in an inhomogeneous electric field in
the pressure range of 0.01–3 atm. In the pulsed and pulse-periodic discharge regimes, we have observed emission bands of the
violet system of cyan, the transition B
2Σ+ → X
2Σ+, which were comparable in intensity with bands of the (2+) system of nitrogen. We show that, in the pulsed regime, the highest intensity of the violet system of cyan is observed in
the N2-CH4 mixture. We show that, in the pulse-periodic discharge in nitrogen with a small amount of a carbon-containing admixture,
upon contracting the discharge, the efficiencies of formation and emission of the violet system of cyan considerably increase.
We confirm that admixtures of oxygen to nitrogen lead to suppression of the emission of the violet system of cyan molecules. 相似文献
9.
Rémi Peyre 《Journal of statistical physics》2009,136(6):1105-1130
We consider a stochastic N-particle model for the spatially homogeneous Boltzmann evolution and prove its convergence to the associated Boltzmann equation
when N⟶∞, with non-asymptotic estimates: for any time T>0, we bound the distance between the empirical measure of the particle system and the measure given by the Boltzmann evolution
in a relevant Hilbert space. The control got is Gaussian, i.e. we prove that the distance is bigger than xN
−1/2 with a probability of type O(e-x2)O(e^{-x^{2}}). The two main ingredients are a control of fluctuations due to the discrete nature of collisions and a kind of Lipschitz
continuity for the Boltzmann collision kernel. We study more extensively the case where our Hilbert space is the homogeneous
negative Sobolev space [(H)\dot]-s\smash {\dot {H}}^{-s}. Then we are only able to give bounds for Maxwellian models; however, numerical computations tend to show that our results
are useful in practice. 相似文献
10.
M. Bender T. Cornelius G.A. Lalazissis J.A. Maruhn W. Nazarewicz P.-G. Reinhard 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):23-28
Recent mass measurements show a substantial weakening of the binding-energy difference δ2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms
of deformed ground states of Hg and Po isotopes.
Received: 25 October 2001 / Accepted: 28 February 2002 相似文献
11.
Hyun Seok Yang 《The European Physical Journal C - Particles and Fields》2009,64(3):445-457
We map noncommutative (NC) U(1) gauge theory on ℝ
C
d
×ℝ
NC
2n
to U(N→∞) Yang–Mills theory on ℝ
C
d
, where ℝ
C
d
is a d-dimensional commutative spacetime while ℝ
NC
2n
is a 2n-dimensional NC space. The resulting U(N) Yang–Mills theory on ℝ
C
d
is equivalent to that obtained by the dimensional reduction of (d+2n)-dimensional U(N) Yang–Mills theory onto ℝ
C
d
. We show that the gauge-Higgs system (A
μ
,Φ
a
) in the U(N→∞) Yang–Mills theory on ℝ
C
d
leads to an emergent geometry in the (d+2n)-dimensional spacetime whose metric was determined by Ward a long time ago. In particular, the 10-dimensional gravity for
d=4 and n=3 corresponds to the emergent geometry arising from the 4-dimensional N=4{\mathcal{N}}=4 vector multiplet in the AdS/CFT duality. We further elucidate the emergent gravity by showing that the gauge-Higgs system
(A
μ
,Φ
a
) in half-BPS configurations describes self-dual Einstein gravity. 相似文献
12.
Jens Böckenhauer David E. Evans Yasuyuki Kawahigashi 《Communications in Mathematical Physics》1999,208(2):429-487
We consider a type III subfactor N⊂N of finite index with a finite system of braided N-N morphisms which includes the irreducible constituents of the dual canonical endomorphism. We apply α-induction and, developing
further some ideas of Ocneanu, we define chiral generators for the double triangle algebra. Using a new concept of intertwining
braiding fusion relations, we show that the chiral generators can be naturally identified with the α-induced sectors. A matrix
Z is defined and shown to commute with the S- and T-matrices arising from the braiding. If the braiding is non-degenerate,
then Z is a “modular invariant mass matrix” in the usual sense of conformal field theory. We show that in that case the fusion rule
algebra of the dual system of M-M morphisms is generated by the images of both kinds of α-induction, and that the structural information about its irreducible
representations is encoded in the mass matrix Z. Our analysis sheds further light on the connection between (the classifications of) modular invariants and subfactors, and
we will construct and analyze modular invariants from SU(n)
k
loop group subfactors in a forthcoming publication, including the treatment of all SU(2)
k
modular invariants.
Received: 13 April 1999 / Accepted: 13 July 1999 相似文献
13.
S.V. Golovkin A.P. Kozhevnikov V.P. Kubarovsky V.F. Kurshetsov L.G. Landsberg V.V. Molchanov V.A. Mukhin S.V. Petrenko V.A. Senko D.V. Vavilov V.A. Victorov V.Z. Kolganov G.S. Lomkatsi A.F. Nilov V.T. Smolyankin 《The European Physical Journal A - Hadrons and Nuclei》1999,5(4):409-416
New data for the diffractive reaction p+N→ [Σ0
K
+] +N at E
p= 70 GeV were obtained with partially upgraded SPHINX setup. The data are in a good agreement with the results of our previous
study of this reaction. In the mass spectrum M(Σ0
K
+) a structure at the threshold region with a mass ∼1810 MeV and a distinct X(2000) peak with M= 1989 ± 6 MeV and γ= 91 ± 20 MeV are observed. Unusual features of the massive X(2000) state (narrow decay width, anomalously
large branching ratio for the decay channel with strange particle emission) make it a serious candidate for cryptoexotic pentaquark
baryon with hidden strangeness |qqqsˉs>. We also present new results on the narrow threshold structure X(1810) with M= 1807 ± 7 MeV and γ= 62 ± 19 MeV which is produced in the region of very small P
2
T < 0.01 GeV2. The possibility of the Coulomb production mechanism for X(1810) is discussed.
Received: 28 April 1999 相似文献
14.
N. Türkan 《Physics of Atomic Nuclei》2007,70(9):1477-1484
We determined the most appropriate Hamiltonian that is needed for calculations of nuclei in the A ≅ 130 region from the viewpoint of the interacting boson model (IBM). Using the best-fitted values of parameters in the Hamiltonian,
we have calculated energy levels and B(E2) values for a number of transitions in some doubly even Nd nuclei of 128 ⩽ N ⩽ 140. The results were compared with the previous experimental and theoretical data, and it is observed that they are in
good agreement. The calculations have been extended to Nd isotopes for which some B(E2) values are still not known.
The text was submitted by the author in English. 相似文献
15.
S. Abd El-Bary S. Abd El-Samad R. Bilger K. -Th. Brinkmann H. Clement M. Dietrich E. Doroshkevich S. Dshemuchadse K. Ehrhardt A. Erhardt W. Eyrich A. Filippi H. Freiesleben M. Fritsch R. Geyer A. Gillitzer C. Hanhart J. Hauffe K. Haug D. Hesselbarth R. Jaekel B. Jakob L. Karsch K. Kilian H. Koch J. Kress E. Kuhlmann S. Marcello S. Marwinski R. Meier K. Möller H. P. Morsch L. Naumann J. Ritman E. Roderburg P. Schönmeier M. Schulte-Wissermann W. Schroeder M. Steinke F. Stinzing G. Y. Sun J. Wächter G. J. Wagner M. Wagner U. Weidlich A. Wilms P. Wintz S. Wirth G. Zhang P. Zupranski 《The European Physical Journal A - Hadrons and Nuclei》2008,37(3):267-277
The two-pion production reaction pp → ppπ+π− was measured with a polarized proton beam at T
p
≈ 750 and 800MeV using the short version of the COSY-TOF spectrometer. The implementation of a delayed-pulse technique for
Quirl and central calorimeter provided positive π+ identification in addition to the standard particle identification, energy determination as well as time-of-flight and angle
measurements. Thus all four-momenta of the emerging particles could be determined with 1–4 overconstraints. Total and differential
cross-sections as well as angular distributions of the vector analyzing power have been obtained. They are compared to previous
data and theoretical calculations. In contrast to predictions we find significant analyzing-power values up to A
y
= 0.3. The data taken in the energy region of the excitation of the Roper resonance confirm that its dominant ππ decay channel
is N
* → Nσ. 相似文献
16.
A. S. Rinat M. F. Taragin M. Viviani 《The European Physical Journal A - Hadrons and Nuclei》2007,31(4):415-416
We use the relation between Structure Functions (SFs) of nuclei A and nucleons N in order to fomulate a criterion which isolates the QE part out of the total inclusive cross-section. From data points around
the QEP we extract the reduced neutron magnetic form factor 〈α
n = G
M
n/μ
n
G
d〉. The latter shows an unexpected decrease up to Q
2 = 10GeV^2, the largest measured. 相似文献
17.
We present results of LDA calculations (band structure, densities of states, Fermi surfaces) for possible iron based superconductor
BaFe2Se3 (Ba123) in normal (paramagnetic) phase. Results are briefly compared with similar data on prototype BaFe2As2 and (K,Cs)Fe2Se2 superconductors. Without doping this system is anti-ferromagnetic with T
Nexp ∼ 250 K and rather complicated magnetic structure. Neutron diffraction experiments indicated the possibility of two possible
spin structures (antiferromagnetically ordered “plaquettes” or “zigzags”), indistinguishable by neutron scattering. Using
LSDA calculated exchange parameters we estimate Neel temperatures for both spin structures within the molecular field approximation
and show τ1 (plaquettes) spin configuration to be more favorable than τ2 (zigzags). 相似文献
18.
J. L. García-Palacios 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,11(2):293-308
Given two strings X and Y of N and M characters respectively, the Longest Common Subsequence (LCS) Problem asks for the longest sequence of (non-contiguous) matches
between X and Y. Using extensive Monte-Carlo simulations for this problem, we find a finite size scaling law of the form for the average LCS length of two random strings of size N over S letters. We provide precise estimates of for .We consider also a related Bernoulli Matching model where the different entries of an array are occupied with a match independently with probability 1/S. On the basis of a cavity-like analysis we find that the length of a longest sequence of matches in that case behaves as
where r=M/N and . This formula agrees very well with our numerical computations. It provides a very good approximation for the Random String
model, the approximation getting more accurate as S increases. The question of the “universality class” of the LCS problem is also considered. Our results for the Bernoulli
Matching model show very good agreement with the scaling predictions of [#!HwaLassig96_PRL!#] for Needleman-Wunsch sequence
alignment. We find however that the variance of the LCS length has a scaling different from Var in the Random String model, suggesting that long-ranged correlations among the matches are relevant in this model. We finally
study the “ground state” properties of this problem. We find that the number of solutions typically grows exponentially with N. In other words, this system does not satisfy “Nernst's principle”. This is also reflected at the level of the overlap between
two LCSs chosen at random, which is found to be self averaging and to approach a definite value q
S
<1 as .
Received: 23 April 1998 / Revised: 30 July 1998 / Accepted: 14 August 1998 相似文献
19.
Aditya M. Vora 《Central European Journal of Physics》2008,6(2):253-262
The theoretical investigations of the superconducting state parameters (SSP) viz. electron-phonon coupling strength λ, Coulomb pseudopotential μ*, transition temperature T
C
, isotope effect exponent α and effective interaction strength N
O
V of six binary La100-C
Ga
C
(C = 16, 20, 22, 24, 26 and 28 at. %) metallic glasses have been reported using Ashcroft’s empty core (EMC) model potential
for the first time. Five local field correction functions proposed by Hartree (H), Taylor (T), Ichimaru-Utsumi (IU), Farid
et al. (F) and Sarkar et al. (S) are used in the present investigation to study the screening influence on the aforesaid properties. It is observed that
the electron-phonon coupling strength λ and the transition temperature T
C
are quite sensitive to the selection of the local field correction functions, whereas the Coulomb pseudopotential μ*, isotope effect exponent α and effective interaction strength N
O
V show weak dependences on the local field correction functions. The T
C
obtained from H-local field correction function are found in qualitative agreement with available experimental data and show
almost linear nature with the concentration (C) of ‘Ga’ element. A linear T
C
equation is proposed by fitting the present outcomes for H-local field correction function, which is in conformity with other
results for the experimental data. Also, the present results are found to be in qualitative agreement with other such earlier
reported data, which confirms the superconducting phase in the metallic glasses.
相似文献
20.
S. Giordano P. L. Palla 《The European Physical Journal B - Condensed Matter and Complex Systems》2012,85(2):59
The electrical and thermal conduction properties of disordered solids and the possible
degradation processes induced by the generation of cracks are central issues in the field
of the heterogeneous materials. However, most of the existing theories are unable to
consider an arbitrary density of cracks. We obtained an exact result for the fields
induced within an elliptic anisotropic inhomogeneity embedded in a different anisotropic
(two-dimensional) conductor. Then, we applied it to show that the degradation process
strongly depends on the statistical orientational distribution of defects: in particular
we theoretically prove that parallel cracks lead to the power law decay
log σ ∼ − log N while random oriented cracks lead to
the exponential law decay log σ ∼ −N (where
σ is the effective conductivity of a region with a large number
N of defects), as recently predicted by numerical findings. 相似文献