Catmull–Clark subdivision surface: Difference between revisions
en>Irtopiste Undid modifications describing R incorrectly as average of recently created edge points |
en>Willpowered m Added link to "barycenter" |
||
Line 1: | Line 1: | ||
= | {{merge|strong interaction|date=December 2013}} | ||
In [[particle physics]], '''Yukawa's interaction''', named after [[Hideki Yukawa]], is an interaction between a [[scalar field (quantum field theory)|scalar field]] ϕ and a [[Dirac field]] ψ of the type | |||
:<math>V \approx g\bar\Psi \phi \Psi</math> (scalar) or <math>g \bar \Psi i\gamma^5 \phi \Psi</math> ([[pseudoscalar]]). | |||
The Yukawa interaction can be used to describe the [[strong nuclear force]] between [[nucleon]]s (which are [[fermion]]s), mediated by [[pion]]s (which are pseudoscalar [[meson]]s). The Yukawa interaction is also used in the [[Standard Model]] to describe the coupling between the [[Higgs field]] and massless [[quark]] and [[lepton]] fields (i.e., the fundamental fermion particles). Through [[spontaneous symmetry breaking]], these fermions acquire a mass proportional to the [[vacuum expectation value]] of the Higgs field. | |||
==The action== | |||
The [[action (physics)|action]] for a [[meson]] field φ interacting with a [[Dirac field|Dirac]] [[baryon]] field ψ is | |||
= | :<math>S[\phi,\psi]=\int d^dx \;\left[ | ||
\mathcal{L}_\mathrm{meson}(\phi) + | |||
\mathcal{L}_\mathrm{Dirac}(\psi) + | |||
\mathcal{L}_\mathrm{Yukawa}(\phi,\psi) \right] | |||
</math> | |||
where the integration is performed over ''d'' dimensions (typically 4 for four-dimensional spacetime). The meson [[Lagrangian]] is given by | |||
:<math>\mathcal{L}_\mathrm{meson}(\phi) = | |||
\frac{1}{2}\partial^\mu \phi \partial_\mu \phi -V(\phi).</math> | |||
Here, <math>V(\phi)</math> is a self-interaction term. For a free-field massive meson, one would have <math>V(\phi)=\frac{1}{2}\mu^2\phi^2</math> where <math>\mu</math> is the mass for the meson. For a ([[renormalizable]]) self-interacting field, one will have <math>V(\phi)=\frac{1}{2}\mu^2\phi^2 + \lambda\phi^4</math> where λ is a coupling constant. This potential is explored in detail in the article on the [[quartic interaction]]. | |||
The free-field Dirac Lagrangian is given by | |||
:<math>\mathcal{L}_\mathrm{Dirac}(\psi) = | |||
\bar{\psi}(i\partial\!\!\!/-m)\psi </math> | |||
where ''m'' is the positive, real mass of the fermion. | |||
The Yukawa interaction term is | |||
:<math>\mathcal{L}_\mathrm{Yukawa}(\phi,\psi) = -g\bar\psi \phi \psi</math> | |||
where ''g'' is the (real) [[coupling constant]] for scalar mesons and | |||
:<math>\mathcal{L}_\mathrm{Yukawa}(\phi,\psi) = -g\bar\psi i\gamma^5 \phi \psi</math> | |||
for pseudoscalar mesons. Putting it all together one can write the above more explicitly as | |||
:<math>S[\phi,\psi]=\int d^dx | |||
\left[\frac{1}{2}\partial^\mu \phi \partial_\mu \phi -V(\phi) + | |||
\bar{\psi}(i\partial\!\!\!/-m)\psi | |||
-g \bar{\psi}\phi\psi \right].</math> | |||
==Classical potential== | |||
If two fermions interact through a Yukawa interaction with Yukawa particle mass <math>\mu</math>, the potential between the two particles, known as the [[Yukawa potential]], will be: | |||
:<math>V(r)=-\frac{g^2}{4\pi} \frac{1}{r} e^{-\mu r}</math> | |||
which is the same as a [[Coulomb potential]] except for the sign and the exponential factor. The sign will make the interaction attractive between all particles (the electromagnetic interaction is repulsive for identical particles). This is explained by the fact that the Yukawa particle has spin zero and even spin always results in an attractive potential. The exponential will give the interaction a finite range, so that particles at great distances will hardly interact any longer. | |||
==Spontaneous symmetry breaking== | |||
Now suppose that the potential <math>V(\phi)</math> has a minimum not at <math>\phi=0</math> but at some non-zero value <math>\phi_0</math>. This can happen if one writes (for example) <math>V(\phi)=\mu^2\phi^2 + \lambda\phi^4</math> and then sets <math>\mu</math> to an imaginary value. In this case, one says that the Lagrangian exhibits [[spontaneous symmetry breaking]]. The non-zero value of <math>\phi</math> is called the [[vacuum expectation value]] of <math>\phi</math>. In the [[Standard Model]], this non-zero value is responsible for the fermion masses, as shown below. | |||
To exhibit the mass term, one re-expresses the action in terms of the field <math>\tilde \phi = \phi-\phi_0</math>, where <math>\phi_0</math> is now understood to be a constant independent of position. We now see that the Yukawa term has a component | |||
:<math>g\phi_0 \bar\psi\psi</math> | |||
and since both ''g'' and <math>\phi_0</math> are constants, this term looks exactly like a mass term for a fermion with mass <math>g\phi_0</math>. This is the mechanism by which spontaneous symmetry breaking gives mass to fermions. The field <math>\tilde\phi</math> is known as the [[Higgs field]]. | |||
==Majorana form== | |||
It's also possible to have a Yukawa interaction between a scalar and a [[Majorana field]]. In fact, the Yukawa interaction involving a scalar and a Dirac spinor can be thought of as a Yukawa interaction involving a scalar with two Majorana spinors of the same mass. Broken out in terms of the two [[Chirality (physics)|chiral]] Majorana spinors, one has | |||
:<math>S[\phi,\chi]=\int d^dx \left[\frac{1}{2}\partial^\mu\phi \partial_\mu \phi -V(\phi)+\chi^\dagger i\bar{\sigma}\cdot\partial\chi+\frac{i}{2}(m+g \phi)\chi^T \sigma^2 \chi-\frac{i}{2}(m+g \phi)^* \chi^\dagger \sigma^2 \chi^*\right]</math> | |||
where ''g'' is a complex [[coupling constant]] and m is a [[complex number]]. | |||
==Feynman rules== | |||
The article [[Yukawa potential]] provides a simple example of the Feynman rules and a calculation of a [[scattering amplitude]] from a [[Feynman diagram]] involving the Yukawa interaction. | |||
==References== | |||
*{{cite book |authorlink=Claude Itzykson |first=Claude |last=Itzykson |first2=Jean-Bernard |last2=Zuber |title=Quantum Field Theory |year=1980 |publisher=McGraw-Hill |location=New York |isbn=0-07-032071-3 }} | |||
*{{cite book |authorlink=James D. Bjorken |first=James D. |last=Bjorken |authorlink2=Sidney Drell |first2=Sidney D. |last2=Drell |title=Relativistic Quantum Mechanics |year=1964 |publisher=McGraw-Hill |location=New York |isbn=0-07-232002-8 }} | |||
*{{cite book |first=Michael E. |last=Peskin |first2=Daniel V. |last2=Schroeder |title=An Introduction to Quantum Field Theory |year=1995 |publisher=Addison-Wesley |isbn=0-201-50397-2 }} | |||
{{Quantum field theories}} | |||
[[Category:Quantum field theory]] | |||
[[Category:Standard Model]] | |||
[[Category:Electroweak theory]] | |||
[[Category:Particle physics]] |
Revision as of 10:44, 14 January 2014
2011 Acura TSX Sport Wagon-There are just some of us all around who would never drive an suv or a minivan but need something practical for family duties. The Acura TSX is one in all my favorite cars in sedan form but I felt that the wagon deserved special mention for bringing luxury, style, class and driving fun into the family transportation segment.
When my hubby brought this finding to the eye of the Ft. Wayne Indiana Toyota dealer, i was told that they would look into the matter. After wasting 7 days before actually doing everything to change this lease, i was told exercises, diet tips too newer. The salesman never offered us this wonderful deal, and the sales manager told us their dealership gave us the best deal toyota tundra off road they would probably. In the same sentence the sales team leader told us we qualified for the cheaper offer. In all honesty they didn't give us the cheapest price they can have. They gave us the highest lease price we were willing with regard to. My credit score is excellent, but it wouldn't have designed a difference for this dealership. After we had shopped around precisely what you want our lease, we might have definitely got a new better deal.
Now, Certain understand why Toyota doesn't offer the SE with rear seat DVD entertainment since most parents discovered that to be an indispensible feature nowadays. Besides that toyota tundra tuning the 3.5 liter V6 emits a lion-like and throaty roar under heavy acceleration that your call don't expect from a clever minivan. Do note I did not have a chance to drive a car the 2011 Honda Odyssey yet when I had the outcome might happen to different. We'll see this year.
Brian Ickler will make his begin of 2011 in the Kyle Busch Motorsports #18 Dollar General Toyota Tundra at Texas Motor Speedway on Friday, June 10. The WinStar World Casino 400K is being run when partnered with the IZOD IndyCar Series Twin 275s on Saturday, June eleventh.
The level came when he was a college junior. He'd just won the co-angler division for this 1994 Bassmaster Top 100 on Lake Norman. Diet plans . only or even bass tournament he'd ever entered.
16-year-old Erik Jones brought home his second top finish because many races in the absolutely no. 51 SUV for Kyle Busch Motorsports, finishing ninth in Sunday's NC Education Lottery 200 at Rockingham Speedway. Jones started at the tail-end belonging to the field in 36th, dropping a lap early along. The "lucky dog" award put him back with the lead lap, and Jones climbed in the top 10 in morrison a pardon stages belonging to the 200-lap race, which was won by Kyle Larson.
Another disadvantage in the Platinum package continually that it adds more chrome trim with regard to an exterior overburdened with it and forces Toyota to stoop a new low no Japanese truck maker has ever gotten to. Yes, the Tundra Platinum comes standard with chrome wheels. They are as tacky just like the optional Red Rock Leather (that really looks orange) and the cheesy half wood/half leather steering interior.
Then either the CrewMax Limited Platinum Package which pulls out all of the stops with vented and heated seats, wood grain style trim and a sunroof. Three cab sizes can be had - regular, double and CrewMax. The Tundra also has three wheelbase and bed lengths. Quite a few options? Not what this means you can build ultimate truck, get style, performance and practicality and always be able to cover it.
In particle physics, Yukawa's interaction, named after Hideki Yukawa, is an interaction between a scalar field ϕ and a Dirac field ψ of the type
- (scalar) or (pseudoscalar).
The Yukawa interaction can be used to describe the strong nuclear force between nucleons (which are fermions), mediated by pions (which are pseudoscalar mesons). The Yukawa interaction is also used in the Standard Model to describe the coupling between the Higgs field and massless quark and lepton fields (i.e., the fundamental fermion particles). Through spontaneous symmetry breaking, these fermions acquire a mass proportional to the vacuum expectation value of the Higgs field.
The action
The action for a meson field φ interacting with a Dirac baryon field ψ is
where the integration is performed over d dimensions (typically 4 for four-dimensional spacetime). The meson Lagrangian is given by
Here, is a self-interaction term. For a free-field massive meson, one would have where is the mass for the meson. For a (renormalizable) self-interacting field, one will have where λ is a coupling constant. This potential is explored in detail in the article on the quartic interaction.
The free-field Dirac Lagrangian is given by
where m is the positive, real mass of the fermion.
The Yukawa interaction term is
where g is the (real) coupling constant for scalar mesons and
for pseudoscalar mesons. Putting it all together one can write the above more explicitly as
Classical potential
If two fermions interact through a Yukawa interaction with Yukawa particle mass , the potential between the two particles, known as the Yukawa potential, will be:
which is the same as a Coulomb potential except for the sign and the exponential factor. The sign will make the interaction attractive between all particles (the electromagnetic interaction is repulsive for identical particles). This is explained by the fact that the Yukawa particle has spin zero and even spin always results in an attractive potential. The exponential will give the interaction a finite range, so that particles at great distances will hardly interact any longer.
Spontaneous symmetry breaking
Now suppose that the potential has a minimum not at but at some non-zero value . This can happen if one writes (for example) and then sets to an imaginary value. In this case, one says that the Lagrangian exhibits spontaneous symmetry breaking. The non-zero value of is called the vacuum expectation value of . In the Standard Model, this non-zero value is responsible for the fermion masses, as shown below.
To exhibit the mass term, one re-expresses the action in terms of the field , where is now understood to be a constant independent of position. We now see that the Yukawa term has a component
and since both g and are constants, this term looks exactly like a mass term for a fermion with mass . This is the mechanism by which spontaneous symmetry breaking gives mass to fermions. The field is known as the Higgs field.
Majorana form
It's also possible to have a Yukawa interaction between a scalar and a Majorana field. In fact, the Yukawa interaction involving a scalar and a Dirac spinor can be thought of as a Yukawa interaction involving a scalar with two Majorana spinors of the same mass. Broken out in terms of the two chiral Majorana spinors, one has
where g is a complex coupling constant and m is a complex number.
Feynman rules
The article Yukawa potential provides a simple example of the Feynman rules and a calculation of a scattering amplitude from a Feynman diagram involving the Yukawa interaction.
References
- 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534 - 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
My blog: http://www.primaboinca.com/view_profile.php?userid=5889534