1,754 research outputs found
Yang-Baxter equation in spin chains with long range interactions
We consider the spin chains with long range interactions and the
spin generalization of the Calogero-Sutherland models. We show that their
properties derive from a transfer matrix obeying the Yang-Baxter equation. We
obtain the expression of the conserved quantities and we diagonalize them.Comment: Saclay-t93/00
On the exactly solvable pairing models for bosons
We propose the new exactly solvable model for bosons corresponding to the
attractive pairing interaction. Using the electrostatic analogy, the solution
of this model in thermodynamic limit is found. The transition from the
superfluid phase with the Bose condensate and the Bogoliubov - type spectrum of
excitations in the weak coupling regime to the incompressible phase with the
gap in the excitation spectrum in the strong coupling regime is observed.Comment: 19 page
Momentum distribution of a freely expanding Lieb-Liniger gas
We numerically study free expansion of a few Lieb-Liniger bosons, which are
initially in the ground state of an infinitely deep hard-wall trap. Numerical
calculation is carried out by employing a standard Fourier transform, as
follows from the Fermi-Bose transformation for a time-dependent Lieb-Liniger
gas. We study the evolution of the momentum distribution, the real-space
single-particle density, and the occupancies of natural orbitals. Our numerical
calculation allows us to explore the behavior of these observables in the
transient regime of the expansion, where they are non-trivially affected by the
particle interactions. We derive analytically (by using the stationary phase
approximation) the formula which connects the asymptotic shape of the momentum
distribution and the initial state. For sufficiently large times the momentum
distribution coincides (up to a simple scaling transformation) with the shape
of the real-space single-particle density (the expansion is asymptotically
ballistic). Our analytical and numerical results are in good agreement.Comment: small changes; references correcte
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Agricultural management and plant selection interactively affect rhizosphere microbial community structure and nitrogen cycling.
BACKGROUND:Rhizosphere microbial communities are key regulators of plant performance, yet few studies have assessed the impact of different management approaches on the rhizosphere microbiomes of major crops. Rhizosphere microbial communities are shaped by interactions between agricultural management and host selection processes, but studies often consider these factors individually rather than in combination. We tested the impacts of management (M) and rhizosphere effects (R) on microbial community structure and co-occurrence networks of maize roots collected from long-term conventionally and organically managed maize-tomato agroecosystems. We also explored the interaction between these factors (M × R) and how it impacts rhizosphere microbial diversity and composition, differential abundance, indicator taxa, co-occurrence network structure, and microbial nitrogen-cycling processes. RESULTS:Host selection processes moderate the influence of agricultural management on rhizosphere microbial communities, although bacteria and fungi respond differently to plant selection and agricultural management. We found that plants recruit management-system-specific taxa and shift N-cycling pathways in the rhizosphere, distinguishing this soil compartment from bulk soil. Rhizosphere microbiomes from conventional and organic systems were more similar in diversity and network structure than communities from their respective bulk soils, and community composition was affected by both M and R effects. In contrast, fungal community composition was affected only by management, and network structure only by plant selection. Quantification of six nitrogen-cycling genes (nifH, amoA [bacterial and archaeal], nirK, nrfA, and nosZ) revealed that only nosZ abundance was affected by management and was higher in the organic system. CONCLUSIONS:Plant selection interacts with conventional and organic management practices to shape rhizosphere microbial community composition, co-occurrence patterns, and at least one nitrogen-cycling process. Reframing research priorities to better understand adaptive plant-microbe feedbacks and include roots as a significant moderating influence of management outcomes could help guide plant-oriented strategies to improve productivity and agroecosystem sustainability
Current induced domain wall dynamics in the presence of spin orbit torques
Current induced domain wall (DW) motion in perpendicularly magnetized
nanostripes in the presence of spin orbit torques is studied. We show using
micromagnetic simulations that the direction of the current induced DW motion
and the associated DW velocity depend on the relative values of the field like
torque (FLT) and the Slonczewski like torques (SLT). The results are well
explained by a collective coordinate model which is used to draw a phase
diagram of the DW dynamics as a function of the FLT and the SLT. We show that a
large increase in the DW velocity can be reached by a proper tuning of both
torques.Comment: 9 pages, 3 figure
sl_2 Gaudin model with Jordanian twist
sl_2 Gaudin model with Jordanian twist is studied. This system can be
obtained as the semiclassical limit of the XXX spin chain deformed by the
Jordanian twist. The appropriate creation operators that yield the Bethe states
of the Gaudin model and consequently its spectrum are defined. Their
commutation relations with the generators of the corresponding loop algebra as
well as with the generating function of integrals of motion are given. The
inner products and norms of Bethe states and the relation to the solutions of
the Knizhnik-Zamolodchikov equations are discussed.Comment: 22 pages; corrected typo
Characterizing and correcting the proper motion bias of the bright Gaia EDR3 sources
In this paper we characterize magnitude-dependent systematics in the proper
motions of the Gaia EDR3 catalog and provide a prescription for their removal.
The reference frame of bright stars (G<13) in EDR3 is known to rotate with
respect to extragalactic objects, but this rotation has proven difficult to
characterize and correct. We employ a sample of binary stars and a sample of
open cluster members to characterize this proper motion bias as a
magnitude-dependent spin of the reference frame. We show that the bias varies
with G magnitude, reaching up to 80 {\mu}as/yr for sources in the range G = 11
- 13, several times the formal EDR3 proper motion uncertainties. We also show
evidence for an additional dependence on the color of the source, with a
magnitude up to 10 {\mu}as/yr. However, a color correction proportional to the
effective wavenumber is unsatisfactory for very red or very blue stars and we
do not recommend its use. We provide a recipe for a magnitude-dependent
correction to align the proper motion of the Gaia EDR3 sources brighter than
G=13 with the International Celestial Reference Frame
Diagonalization of an Integrable Discretization of the Repulsive Delta Bose Gas on the Circle
We introduce an integrable lattice discretization of the quantum system of n
bosonic particles on a ring interacting pairwise via repulsive delta
potentials. The corresponding (finite-dimensional) spectral problem of the
integrable lattice model is solved by means of the Bethe Ansatz method. The
resulting eigenfunctions turn out to be given by specializations of the
Hall-Littlewood polynomials. In the continuum limit the solution of the
repulsive delta Bose gas due to Lieb and Liniger is recovered, including the
orthogonality of the Bethe wave functions first proved by Dorlas (extending
previous work of C.N. Yang and C.P. Yang).Comment: 25 pages, LaTe
Magnetic anomalies in Nd6Co(1.67)Si3: Surprising first order transitions in the low-temperature isothermal magnetization
We present the results of magnetic measurements on Nd6Co(1.67)Si3, a compound
recently reported to crystallize in a hexagonal structure (space group P6_3/m)
and to undergo long range magnetic ordering below 84 K. The results reveal that
the magnetism of this compound is quite complex with additional magnetic
anomalies near 50 and 20 K. There are qualitative changes in the isothermal
magnetization behavior with the variation of temperature. Notably, there is a
field-induced spin reorientation as the temperature is lowered below 20 K. A
finding we stress is that this transition is discontinuous for 1.8K in the
virgin curve, but the first order character appears only after a field-cycling
for a narrow higher temperature range near 5 K. Thus, this compound serves as
an example for the stabilisation of first-order transition induced by
magnetic-field-cycling. The issues of 'Phase co-existence' and 'meta-stability'
after a field-cycling at low temperatures in this compound are also addressed
Attempted Bethe ansatz solution for one-dimensional directed polymers in random media
We study the statistical properties of one-dimensional directed polymers in a
short-range random potential by mapping the replicated problem to a many body
quantum boson system with attractive interactions. We find the full set of
eigenvalues and eigenfunctions of the many-body system and perform the
summation over the entire spectrum of excited states. The analytic continuation
of the obtained exact expression for the replica partition function from
integer to non-integer replica parameter N turns out to be ambiguous.
Performing the analytic continuation simply by assuming that the parameter N
can take arbitrary complex values, and going to the thermodynamic limit of the
original directed polymer problem, we obtain the explicit universal expression
for the probability distribution function of free energy fluctuations.Comment: 32 pages, 1 figur
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