12.07.2015 Views

Vol. 2 - The World of Mathematical Equations

Vol. 2 - The World of Mathematical Equations

Vol. 2 - The World of Mathematical Equations

SHOW MORE
SHOW LESS

You also want an ePaper? Increase the reach of your titles

YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.

April, 2008 PROGRESS IN PHYSICS <strong>Vol</strong>ume 2<strong>The</strong>n if we interchange z 1 and z 3 we haveW(z 3 ; w)W(w; z 2 )W(z 1 ; w)W(w; z 4 ) == e ^t log[ (z 1 z 3)] Ae^t log(z 4 z 2) :From (67) and (68) as a choice <strong>of</strong> branch we haveW(z 3 ; w)W(w; z 2 )W(z 1 ; w)W(w; z 4 ) == RW(z 1 ; w)W(w; z 2 )W(z 3 ; w)W(w; z 4 ) ;(68)(69)where R = e i^t is the monodromy <strong>of</strong> the KZ equation. In(69) z 1 and z 3 denote two points on a closed curve such thatalong the direction <strong>of</strong> the curve the point z 1 is before the pointz 3 and in this case we choose a branch such that the angle <strong>of</strong>z 3 z 1 minus the angle <strong>of</strong> z 1 z 3 is equal to .RemarkWe may use other representations <strong>of</strong> the productW(z 1 ; z 2 )W(z 3 ; z 4 ). For example we may use the followingrepresentation:W(z 1 ; w)W(w; z 2 )W(z 3 ; w)W(w; z 4 ) == e ^t log(z 1 z 3) e 2^t log(z 1 w) e 2^t log(z 3 w) Ae^t log(z 4 z 2) e 2^t log(z 4 w) e 2^t log(z 2 w) :(70)<strong>The</strong>n the interchange <strong>of</strong> z 1 and z 3 changes only z 1 z 3to z 3 z 1 . Thus the formula (69) holds. Similarly all otherrepresentations <strong>of</strong> W(z 1 ; z 2 )W(z 3 ; z 4 ) will give the sameresult.Now from (69) we can take a convention that the ordering(66) represents that the curve represented by W(z 1 ; z 2 )is up-crossing the curve represented by W(z 3 ; z 4 ) while (65)represents zero crossing <strong>of</strong> these two curves.Similarly from the dual KZ equation as a choice <strong>of</strong> branchwhich is consistent with the above formula we haveW(z 1 ; w)W(w; z 4 )W(z 3 ; w)W(w; z 2 ) == W(z 1 ; w)W(w; z 2 )W(z 3 ; w)W(w; z 4 )R 1 ;(71)where z 2 is before z 4 . We take a convention that the orderingin (71) represents that the curve represented by W(z 1 ; z 2 )is under-crossing the curve represented by W(z 3 ; z 4 ). Herealong the orientation <strong>of</strong> a closed curve the piece <strong>of</strong> curverepresented by W(z 1 ; z 2 ) is before the piece <strong>of</strong> curve representedby W(z 3 ; z 4 ). In this case since the angle <strong>of</strong> z 3 z 1minus the angle <strong>of</strong> z 1 z 3 is equal to we have that the angle<strong>of</strong> z 4 z 2 minus the angle <strong>of</strong> z 2 z 4 is also equal to and this gives the R 1 in this formula (71).From (69) and (71) we haveW(z 3 ; z 4 )W(z 1 ; z 2 ) = RW(z 1 ; z 2 )W(z 3 ; z 4 )R 1 ; (72)where z 1 and z 2 denote the end points <strong>of</strong> a curve which isbefore a curve with end points z 3 and z 4 . From (72) wesee that the algebraic structure <strong>of</strong> these quantum Wilson linesW(z; z0 ) is analogous to the quasi-triangular quantum group[66, 69].8 Computation <strong>of</strong> quantum Dirac-Wilson loopConsider again the quantum Wilson line W(z 1 ; z 4 ) given byW(z 1 ; z 4 ) = W(z 1 ; z 2 )W(z 2 ; z 4 ). Let us set z 1 = z 4 . In thiscase the quantum Wilson line forms a closed loop. Now in(61) with z 1 = z 4 we have that the quantities e ^t log(z 1 z 2 )and e^t log(z 1 z 2) which come from the two-side KZ equationscancel each other and from the multi-valued property <strong>of</strong>the log function we have:W(z 1 ; z 1 ) = R N A 14 ; N = 0;1;2; : : : (73)where R = e i^t is the monodromy <strong>of</strong> the KZ equation [69].RemarkIt is clear that if we use other representation <strong>of</strong> thequantum Wilson loop W(z 1 ; z 1 ) (such as the representationW(z 1 ; z 1 ) = W(z 1 ; w 1 )W(w 1 ; w 2 )W(w 2 ; z 1 )) then we willget the same result as (73).Remark For simplicity we shall drop the subscript <strong>of</strong> A 14in (73) and simply write A 14 = A.9 Winding number <strong>of</strong> Dirac-Wilson loop as quantizationWe have the equation (73) where the integer N is as a windingnumber. <strong>The</strong>n when the gauge group is U(1) we haveW(z 1 ; z 1 ) = R N U(1)A ; (74)where R U(1) denotes the monodromy <strong>of</strong> the KZ equation forU(1). We haveR N U(1) = e iN e2 0k0+g0 ; N = 0;1;2; : : : (75)where the constant e 0 denotes the bare electric charge (andg 0 = 0 for U(1) group). <strong>The</strong> winding number N is as thequantization property <strong>of</strong> photon.We show in the followingSection that the Dirac-Wilson loop W(z 1 ; z 1 ) with theabelian U(1) group is a model <strong>of</strong> the photon.10 Magnetic monopole is a photon with a specific frequencyWe see that the Dirac-Wilson loop is an exactly solvable nonlinearobservable. Thus we may regard it as a quantum soliton<strong>of</strong> the above gauge theory. In particular for the abelian gaugetheory with U(1) as gauge group we regard the Dirac-Wilsonloop as a quantum soliton <strong>of</strong> the electromagnetic field. Wenow want to show that this soliton has all the properties <strong>of</strong>photon and thus we may identify it with the photon.First we see that from (75) it has discrete energy levels <strong>of</strong>light-quantum given byh := N e2 0k 0; N = 0; 1; 2; 3; : : : (76)Sze Kui Ng. New Approach to Quantum Electrodynamics 25

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!