Spin (von englisch spin ‚Drehung', ‚Drall') ist in der Teilchenphysik der Eigendrehimpuls von Teilchen. Bei den fundamentalen Teilchen ist er wie die Masse. Der Spin ist eine eigenartige Eigenschaft des Elektrons. Jedes Elektron hat den Spin 1/2. Man kann ihn sich, vereinfacht, als eine Rotation des Elektrons um seine. Spin ist in der Teilchenphysik der Eigendrehimpuls von Teilchen. Bei den fundamentalen Teilchen ist er wie die Masse eine unveränderliche innere Teilcheneigenschaft. Er beträgt ein halb- oder ganzzahliges Vielfaches des reduzierten planckschen.
Freunde kennenlernen, Chat, Online-Spiele und mehrSpin (von englisch spin ‚Drehung', ‚Drall') ist in der Teilchenphysik der Eigendrehimpuls von Teilchen. Bei den fundamentalen Teilchen ist er wie die Masse. Im Falle von akademischen Spin - offs als Untergruppe junger technologiebasierter Unternehmen stellt dies aufgrund von Eigenheiten der Kerntechnologie und. dem Erfolg 12 CEOs von universitären Spin- offs (UK) Qualitative Auswertung Mutterorganisation beeinflussen den Wachstums- verlauf der Spin-offs positiv.
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We are thankful for obscure words. Can you spell these 10 commonly misspelled words? Build a city of skyscrapers—one synonym at a time.
Login or Register. Save Word. Keep scrolling for more. Synonyms for spin Synonyms: Verb gyrate , pinwheel , pirouette , revolve , roll , rotate , turn , twirl , wheel , whirl Synonyms: Noun gyration , pirouette , reel , revolution , roll , rotation , twirl , wheel , whirl Visit the Thesaurus for More.
Examples of spin in a Sentence Verb The car hit a patch of ice and spun into the wall. Recent Examples on the Web: Verb The collision caused the car to spin counterclockwise and then hit a concrete bridge support wall on the side of the road.
First Known Use of spin Verb before the 12th century, in the meaning defined at intransitive sense 1 Noun , in the meaning defined at sense 1a.
Learn More about spin. Time Traveler for spin The first known use of spin was before the 12th century See more words from the same century.
From the Editors at Merriam-Webster. The Plate trick and Möbius strip give non-quantum analogies. A spin-zero particle can only have a single quantum state, even after torque is applied.
Rotating a spin-2 particle degrees can bring it back to the same quantum state and a spin-4 particle should be rotated 90 degrees to bring it back to the same quantum state.
The spin-2 particle can be analogous to a straight stick that looks the same even after it is rotated degrees and a spin-0 particle can be imagined as sphere, which looks the same after whatever angle it is turned through.
Spin obeys commutation relations analogous to those of the orbital angular momentum :. It follows as with angular momentum that the eigenvectors of S 2 and S z expressed as kets in the total S basis are:.
The spin raising and lowering operators acting on these eigenvectors give:. But unlike orbital angular momentum the eigenvectors are not spherical harmonics.
There is also no reason to exclude half-integer values of s and m s. In addition to their other properties, all quantum mechanical particles possess an intrinsic spin though this value may be equal to zero.
One distinguishes bosons integer spin and fermions half-integer spin. The total angular momentum conserved in interaction processes is then the sum of the orbital angular momentum and the spin.
For systems of N identical particles this is related to the Pauli exclusion principle , which states that by interchanges of any two of the N particles one must have.
In quantum mechanics all particles are either bosons or fermions. In some speculative relativistic quantum field theories " supersymmetric " particles also exist, where linear combinations of bosonic and fermionic components appear.
The above permutation postulate for N -particle state functions has most-important consequences in daily life, e.
As described above, quantum mechanics states that components of angular momentum measured along any direction can only take a number of discrete values.
The most convenient quantum mechanical description of particle's spin is therefore with a set of complex numbers corresponding to amplitudes of finding a given value of projection of its intrinsic angular momentum on a given axis.
Since these numbers depend on the choice of the axis, they transform into each other non-trivially when this axis is rotated. It is clear that the transformation law must be linear, so we can represent it by associating a matrix with each rotation, and the product of two transformation matrices corresponding to rotations A and B must be equal up to phase to the matrix representing rotation AB.
Further, rotations preserve the quantum mechanical inner product, and so should our transformation matrices:. Mathematically speaking, these matrices furnish a unitary projective representation of the rotation group SO 3.
Each such representation corresponds to a representation of the covering group of SO 3 , which is SU 2. Starting with S x. Using the spin operator commutation relations , we see that the commutators evaluate to i S y for the odd terms in the series, and to S x for all of the even terms.
Note that since we only relied on the spin operator commutation relations, this proof holds for any dimension i. A generic rotation in 3-dimensional space can be built by compounding operators of this type using Euler angles :.
An irreducible representation of this group of operators is furnished by the Wigner D-matrix :. Recalling that a generic spin state can be written as a superposition of states with definite m , we see that if s is an integer, the values of m are all integers, and this matrix corresponds to the identity operator.
This fact is a crucial element of the proof of the spin-statistics theorem. We could try the same approach to determine the behavior of spin under general Lorentz transformations , but we would immediately discover a major obstacle.
Unlike SO 3 , the group of Lorentz transformations SO 3,1 is non-compact and therefore does not have any faithful, unitary, finite-dimensional representations.
These spinors transform under Lorentz transformations according to the law. It can be shown that the scalar product. The corresponding normalized eigenvectors are:.
Because any eigenvector multiplied by a constant is still an eigenvector, there is ambiguity about the overall sign. In this article, the convention is chosen to make the first element imaginary and negative if there is a sign ambiguity.
The present convention is used by software such as sympy; while many physics textbooks, such as Sakurai and Griffiths, prefer to make it real and positive.
By the postulates of quantum mechanics , an experiment designed to measure the electron spin on the x -, y -, or z -axis can only yield an eigenvalue of the corresponding spin operator S x , S y or S z on that axis, i.
The quantum state of a particle with respect to spin , can be represented by a two component spinor :. Following the measurement, the spin state of the particle will collapse into the corresponding eigenstate.
The operator to measure spin along an arbitrary axis direction is easily obtained from the Pauli spin matrices. Then the operator for spin in this direction is simply.
This method of finding the operator for spin in an arbitrary direction generalizes to higher spin states, one takes the dot product of the direction with a vector of the three operators for the three x -, y -, z -axis directions.
In quantum mechanics, vectors are termed "normalized" when multiplied by a normalizing factor, which results in the vector having a length of unity.
Since the Pauli matrices do not commute , measurements of spin along the different axes are incompatible. This means that if, for example, we know the spin along the x -axis, and we then measure the spin along the y -axis, we have invalidated our previous knowledge of the x -axis spin.
This can be seen from the property of the eigenvectors i. This implies that the original measurement of the spin along the x-axis is no longer valid, since the spin along the x -axis will now be measured to have either eigenvalue with equal probability.
By taking Kronecker products of this representation with itself repeatedly, one may construct all higher irreducible representations. That is, the resulting spin operators for higher spin systems in three spatial dimensions, for arbitrarily large s , can be calculated using this spin operator and ladder operators.
The resulting irreducible representations yield the following spin matrices and eigenvalues in the z-basis. Also useful in the quantum mechanics of multiparticle systems, the general Pauli group G n is defined to consist of all n -fold tensor products of Pauli matrices.
The analog formula of Euler's formula in terms of the Pauli matrices :. For example, see the isotopes of bismuth in which the List of isotopes includes the column Nuclear spin and parity.
Spin has important theoretical implications and practical applications. Well-established direct applications of spin include:.
Electron spin plays an important role in magnetism , with applications for instance in computer memories. The manipulation of nuclear spin by radiofrequency waves nuclear magnetic resonance is important in chemical spectroscopy and medical imaging.
Spin-orbit coupling leads to the fine structure of atomic spectra, which is used in atomic clocks and in the modern definition of the second.
Precise measurements of the g -factor of the electron have played an important role in the development and verification of quantum electrodynamics.
Photon spin is associated with the polarization of light photon polarization. Lege dir hier deine persönliche Homepage mit kostenlosem Blog , Gästebuch, Fotos und vielem mehr an.
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