scholarly journals Study of Approximations for Electron?Atom Direct Reactions

1983 ◽  
Vol 36 (5) ◽  
pp. 665 ◽  
Author(s):  
IE McCarthy ◽  
AT Stelbovics
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Experimental Error ◽  
Degrees Of Freedom ◽  
Body System ◽  
Many Body ◽  
Coupled Channels ◽  
Direct Reactions ◽  
Many Body Systems ◽  
Three Body

The electron-hydrogen system is a true three-body system which provides an excellent test for theories of reactions in many-body systems that approximately involve only three-body degrees of freedom. The coupled-channels optical approximation reproduces experimental data in most cases within experimental error. The approximation may be extended to a larger space of coupled channels by various approximations which are tested with the example of 54�42 e V electron scattering on the Is, 2s and 2p space for hydrogen, extended by the addition of 3s and 3p channels. Channels outside this five-state space are treated by including the corresponding polarization potentials.

scholarly journals Using Matrix-Product States for Open Quantum Many-Body Systems: Efficient Algorithms for Markovian and Non-Markovian Time-Evolution

Entropy ◽  
2020 ◽  
Vol 22 (9) ◽  
pp. 984
Author(s):  
Regina Finsterhölzl ◽  
Manuel Katzer ◽  
Andreas Knorr ◽  
Alexander Carmele
Keyword(s):  
Time Evolution ◽  
Nearest Neighbor ◽  
Matrix Product ◽  
Body System ◽  
Many Body ◽  
Initial State ◽  
Matrix Product States ◽  
Open Quantum ◽  
Many Body Systems ◽  
The Many

This paper presents an efficient algorithm for the time evolution of open quantum many-body systems using matrix-product states (MPS) proposing a convenient structure of the MPS-architecture, which exploits the initial state of system and reservoir. By doing so, numerically expensive re-ordering protocols are circumvented. It is applicable to systems with a Markovian type of interaction, where only the present state of the reservoir needs to be taken into account. Its adaption to a non-Markovian type of interaction between the many-body system and the reservoir is demonstrated, where the information backflow from the reservoir needs to be included in the computation. Also, the derivation of the basis in the quantum stochastic Schrödinger picture is shown. As a paradigmatic model, the Heisenberg spin chain with nearest-neighbor interaction is used. It is demonstrated that the algorithm allows for the access of large systems sizes. As an example for a non-Markovian type of interaction, the generation of highly unusual steady states in the many-body system with coherent feedback control is demonstrated for a chain length of N=30.

Mesonic and isobar degrees of freedom in the ground state of the nuclear many-body system

1978 ◽  
Vol 18 (5) ◽  
pp. 2416-2429 ◽  
Author(s):  
M. R. Anastasio ◽  
Amand Faessler ◽  
H. Müther ◽  
K. Holinde ◽  
R. Machleidt
Keyword(s):  
Ground State ◽  
Degrees Of Freedom ◽  
Body System ◽  
Many Body

scholarly journals By-passing fluctuation theorems

Quantum ◽  
2020 ◽  
Vol 4 ◽  
pp. 231
Author(s):  
Paul Boes ◽  
Rodrigo Gallego ◽  
Nelly H. Y. Ng ◽  
Jens Eisert ◽  
Henrik Wilming
Keyword(s):  
Degrees Of Freedom ◽  
Quantum Thermodynamics ◽  
Many Body ◽  
Fluctuation Theorems ◽  
Macroscopic States ◽  
Many Body Systems ◽  
Highly Correlated ◽  
Positive Work ◽  
Thermodynamical Processes ◽  
Reduced State

Fluctuation theorems impose constraints on possible work extraction probabilities in thermodynamical processes. These constraints are stronger than the usual second law, which is concerned only with average values. Here, we show that such constraints, expressed in the form of the Jarzysnki equality, can be by-passed if one allows for the use of catalysts---additional degrees of freedom that may become correlated with the system from which work is extracted, but whose reduced state remains unchanged so that they can be re-used. This violation can be achieved both for small systems but also for macroscopic many-body systems, and leads to positive work extraction per particle with finite probability from macroscopic states in equilibrium. In addition to studying such violations for a single system, we also discuss the scenario in which many parties use the same catalyst to induce local transitions. We show that there exist catalytic processes that lead to highly correlated work distributions, expected to have implications for stochastic and quantum thermodynamics.

Three-body Algebraic Theory

1995 ◽  
Author(s):  
F. Iachello ◽  
R. D. Levine
Keyword(s):  
Quantum Mechanics ◽  
Degrees Of Freedom ◽  
Differential Operators ◽  
Algebraic Theory ◽  
Many Body ◽  
Two Body Problem ◽  
Three Body ◽  
Schrödinger Picture ◽  
Algebraic Operators

In the previous chapter we discussed the usual realization of many-body quantum mechanics in terms of differential operators (Schrödinger picture). As in the case of the two-body problem, it is possible to formulate many-body quantum mechanics in terms of algebraic operators. This is done by introducing, for each coordinate r1,r2,... and momentum p1, p2, . . . , boson creation and annihilation operators, b†iα, biα. The index i runs over the number of relevant degrees of freedom, while the index α runs from 1 to n + 1, where n is the number of space dimensions (see note 3 of Chapter 2). The boson operators satisfy the usual commutation relations, which are for i ≠ j, . . . [biα, b†jα´] = 0, [biα, bjα´] = 0,. . . . . .[bjα, b†iα´] = 0, [b†jα, b†iα´] = 0,. . . . . . [biα, b†iα´] = ẟαα´, [biα, b†iα´] = 0, [b†iα, b†iα´] = 0. . . .

scholarly journals On the widths and binding energies of K− nuclear states and the role of K− multi-nucleon interactions

2018 ◽  
Vol 181 ◽  
pp. 01009
Author(s):  
Jaroslava Hrtankova ◽  
Jiří Mareš
Keyword(s):  
Bound States ◽  
Binding Energies ◽  
Many Body ◽  
Nucleon Interaction ◽  
Substantial Impact ◽  
Coupled Channels ◽  
Self Consistent ◽  
Interaction Term ◽  
Many Body Systems

We report on our recent self-consistent calculations of K− nuclear quasi-bound states using K− optical potentials derived from chirally motivated meson-baryon coupled channels models [1, 2]. The K− single-nucleon potentials were supplemented by a phenomenological K− multi-nucleon interaction term introduced to achieve good fits to K− atom data. We demonstrate a substantial impact of the K− multi-nucleon absorption on the widths of K− nuclear states. If such states ever exist in nuclear many-body systems, their widths are excessively large to allow observation.

scholarly journals Thermalization of Finite Many-Body Systems by a Collision Model

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1182 ◽  
Author(s):  
Onat Arısoy ◽  
Steve Campbell ◽  
Özgür E. Müstecaplıoğlu
Keyword(s):  
Weak Coupling ◽  
Target System ◽  
Model Description ◽  
Body System ◽  
Weak Coupling Regime ◽  
Many Body ◽  
Collision Model ◽  
System Transition ◽  
Many Body Systems ◽  
Thermal States

We construct a collision model description of the thermalization of a finite many-body system by using careful derivation of the corresponding Lindblad-type master equation in the weak coupling regime. Using the example of a two-level target system, we show that collision model thermalization is crucially dependent on the various relevant system and bath timescales and on ensuring that the environment is composed of ancillae which are resonant with the system transition frequencies. Using this, we extend our analysis to show that our collision model can lead to thermalization for certain classes of many-body systems. We establish that for classically correlated systems our approach is effective, while we also highlight its shortcomings, in particular with regards to reaching entangled thermal states.

FOUR-BODY CONTINUUM-DISCRETIZED COUPLED-CHANNEL CALCULATIONS APPLIED TO 6He REACTIONS AROUND THE COULOMB BARRIER

2011 ◽  
Vol 20 (04) ◽  
pp. 947-952 ◽  
Author(s):  
M. RODRÍGUEZ-GALLARDO ◽  
A. M. MORO
Keyword(s):  
Harmonic Oscillator ◽  
Cross Section ◽  
Coulomb Barrier ◽  
Elastic Cross Section ◽  
Body System ◽  
Weakly Bound ◽  
Discretization Methods ◽  
Coupled Channels ◽  
Three Body ◽  
Coupled Channel

The scattering of a weakly bound three-body system by a target is studied within the four-body continuum-discretized coupled-channels (4b-CDCC) framework. Two different methods, the transformed harmonic oscillator (THO) method and the binning procedure, are used for discretizing the three-body continuum. The formalism is applied to different reactions induced by the Borromean nucleus 6 He at energies around the Coulomb barrier: 6 He +64 Zn at 13.6 MeV, 6 He +120 Sn at 17.4 MeV, and 6 He +208 Pb at 22 MeV. Elastic cross section distributions are presented for these reactions comparing both discretization methods, THO and binning, as the mass of the target increases.

scholarly journals Self-consistent effective Hamiltonian theory for fermionic many-body systems

2020 ◽  
pp. 2150019
Author(s):  
Xindong Wang ◽  
Hai-Ping Cheng
Keyword(s):  
Hubbard Model ◽  
Order Parameter ◽  
Cooper Pair ◽  
Effective Hamiltonian ◽  
Two Dimensional ◽  
Body System ◽  
Many Body ◽  
Hamiltonian Theory ◽  
Self Consistent ◽  
Many Body Systems

Using a separable many-body variational wavefunction, we formulate a self-consistent effective Hamiltonian theory for fermionic many-body system. The theory is applied to the two-dimensional (2D) Hubbard model as an example to demonstrate its capability and computational effectiveness. Most remarkably for the Hubbard model in 2D, a highly unconventional quadruple-fermion non-Cooper pair order parameter is discovered.

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