angina-pectoris
发表于 2025-3-25 04:21:17
The XY Model, combining these fermion operators into new ‘quasiparticle’ operators that are still fermions. The ground state is then a state in which all eigenstates of these operators are occupied up to the ‘Fermi surface’. It is then possible to calculate the ground state energy of this system.
Glaci冰
发表于 2025-3-25 08:43:46
Spin-Wave Theory, simple and the results are usually exact. The antiferromagnetic version is more complicated and the results are approximate. However, these results are still in reasonable correspondence with exact results, where these are known, and the best of other approximate methods.
commensurate
发表于 2025-3-25 12:52:21
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食料
发表于 2025-3-25 17:50:37
Besondere Herstellungsverfahren,at happens when there are large numbers of interacting spins. Finally we introduce the infinite linear (i.e. one-dimensional) chain of spin-1/2 atoms. Some preliminary classical results for this model are given as background for the full quantum treatment which will be studied in detail in the following chapters.
镇压
发表于 2025-3-25 21:18:59
Book 2010 remain to be answered. Their intrinsically quantum mechanical nature and the large (usually effectively infinite) number of spins in macroscopic materials often leads to unexpected or counter-intuitive results and insights. Spin systems are not only the basic models for a whole host of magnetic mat
Ganglion-Cyst
发表于 2025-3-26 03:53:42
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首创精神
发表于 2025-3-26 06:05:51
Antiferromagnetic Spin Waves,ined using conventional antiferromagnetic spin-wave theory (covered in a later chapter). We finish this chapter with a discussion of the somewhat unexpected behaviour of the excitation spectrum when an external magnetic field is present.
CAMP
发表于 2025-3-26 09:01:54
Maschinen für das Zusammenfügen der Theiles of the order of 20 for full diagonalisation and 40 for partial diagonalisation. Clearly the ground state energy and the energies of the elementary excitations are obtained directly. Also the partition function can be constructed directly for full diagonalisation because all the eigenvalues are kno
盖他为秘密
发表于 2025-3-26 12:54:50
,Die Maschinen für die Blechbearbeitung,enberg model on the linear chain is used as a test-case for all of these methods. We show that even simple applications of these methods give improved results for the ground-state energy compared to the classical result.
消瘦
发表于 2025-3-26 18:20:35
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