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Higgs boson's mechanism for giving mass? 
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#19
Oct1413, 05:34 AM

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#20
Oct1513, 08:30 AM

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#21
Oct1713, 11:17 PM

P: 518

Here's how I like to explain it. The Higgs particle gets a nonzero field value from interacting with itself. That nonzero field value then makes it always there for particles that interact with it, and that's what gives those particles their masses.



#22
Oct1813, 06:22 AM

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But you should distinguish between the Higgs field and the Higgs particle, which is the excitation of the field. Gauge bosons acquire mass through their coupling to the VEV, not through Yukawatype couplings to the field directly.



#23
Oct1813, 10:16 AM

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Gauge particles don't just couple to the Higgs VEV, but to the entire Higgs field, as elementary fermions do.



#24
Oct1813, 12:01 PM

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Of course, but the gauge boson mass terms arise specifically from the coupling with the VEV: [itex]M \sim gv[/itex], where [itex]v[/itex] is the VEV and [itex]g[/itex] the coupling.



#25
Oct1813, 11:44 PM

P: 518

The elementaryfermion mass terms also arise in that fashion.
Rather schematically, [tex]L = (g\cdot W)\cdot H^2 + (y \cdot \psi_R \cdot H \cdot \psi_L) + \text{H.C.}[/tex] for the gauge particles and the elementary fermions. [tex]H = v + \phi[/tex] Higgs particle > VEV + excitations So it works the same for both: [tex]L = (m_W)^2 W^2 (1 + \phi/v)^2 + (m_f \cdot \psi_R \cdot \psi_L) (1 + \phi/v) + \text{H.C.}[/tex] where m_{W} = g*v and m_{f} = y*v. 


#26
Oct1913, 03:30 AM

P: 77

Ok guys, thanks for the explanations. I wonder what Veltman's pov is on this. How does the cosmological constant fit in?



#27
Oct1913, 07:11 AM

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#28
Oct1913, 07:12 AM

P: 518

The cosmological constant is a sort of vacuum energy density, with pressure =  that density. Notice the minus sign.
The big problem with it is that its value is much lower than what one might expect from quantum gravity. One naively expects the Planck density, but its observed value is about 10^(120) that. Relative to electroweak symmetry breaking, that discrepancy is about 10^(52)  10^(50). I think that it's a problem for quantum gravity, and that is still an unsolved problem. 


#29
Oct1913, 08:41 AM

P: 77

Veltman states that the cosmological constant in the Higgs model takes the form C= m2M2 / 8g2 ,
which is way too large. http://igiturarchive.library.uu.nl/...temVeltman.pdf 


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