/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Q51P 聽Recall that a covariant 4-vect... [FREE SOLUTION] | 91影视

91影视

Recall that a covariant 4-vector is obtained from a contravariant one by changing the sign of the zeroth component. The same goes for tensors: When you 鈥渓ower an index鈥 to make it covariant, you change the sign if that index is zero. Compute the tensor invariants

F渭惫F渭惫,G渭惫G渭惫andF渭惫G渭惫

in terms of E and B. Compare Prob. 12.47.

Short Answer

Expert verified

The tensor invariants are F渭惫F渭惫=2B2-E2c2G渭惫G渭惫=2E2c2-B2andF渭惫G渭惫=-4cE.B

Step by step solution

01

Expression for the Product of  and :

Write the expression for the product of F渭惫F渭惫

F渭惫F渭惫=F00F00-F01F01-F02F02-F03F03-F10F10-F20F20-F30F30+F11F11+F12F12+F13F13+F21F21+F22F22+F23F23+F31F31+F32F32+F33F33Here,F00=0,F01=Exc,F02=Eyc,F03=Ezc,F12=Bz,F31=ByandF23=Bx .......(1)

Write the expression for the product of G渭惫G渭惫

G渭惫G渭惫=G00G00-G01G01-G02G02-G03G03-G10G10-G20G20-G30G30+G11G11+G12G12+G13G13+G21G21+G22G22+G23G23+G31G31+G32G32+G33G33Here,G00=0,G01,G12=Bz,G31=By,G23=Bx,Exc,G02=EycandG03=Ezc ......(2)

02

Determine the Product of :

Substitute F00=0,F01=Exc,F02=Eyc,F03=Ezc,F12=Bz,F31=ByandF23=Bxin equation (1).

F渭惫F渭惫=0-Exc2--Eyc2-Ezc2-Exc2-Eyc2-Ezc2+0+Bz2+By2+Bx2+0+Bz2+By2+Bx2+0F渭惫F渭惫=-2Ex2c2-2Ey2c2-2Ez2c2+2Bx2+2By2+2Bz2Here,Bx+By+Bz=BandEx+Ex+Ex=E

So, the above equation becomes,

F渭谓F渭谓=-2Ex2c2-2Ey2c2-2Ez2c2+2Bx2+2By2+2Bz2F渭谓F渭谓=-2c2Ex2+Ey2+Ez2+2Bx2+By2+Bz2F渭谓F渭谓=-2E2c2+2B2F渭谓F渭谓=2B2E2c2

03

Determine the Product of :

Substitute G00=0,G01=Bx,G01=By,G01=Bz,G12=EZc,G31=EycandG31=Excin equation (2).

G渭谓G渭谓=0-Bx2-Bx2-Bx2-Bx2-Bx2-Bx2+0+-Ezc2+-Eyc+-Ezc+0+-Exc+-Eyc+-Exc+0G渭谓G渭谓=-2Bx2-2Bx2-2Bx2+Ez2c2+Ey2c2+Ez2c2+Ex2c2+Ez2c2+Ex2c2G渭谓G渭谓=-2Bx2+By2+Bz2+2c2Ex2+Ey2+Ez2

On further solving,

G渭谓G渭谓=-2B2+2c2E2G渭谓G渭谓=2E2c2-B2

04

Determine the Product of :

Write the expression for the product of F渭谓F渭谓

role="math" localid="1654678337382" F渭谓F渭谓=-2F01G01+F02G02+F03G03+2F12G12+F13G13+F23G23

Substitute, role="math" localid="1654679206876" F01=Exc,F02=Eyc,F03=Ezc,F12=Bz,F31=BzandF23=Bx

G01=Bx,G02=By,G03=BzG12=-Ezc,G31=-EzcandG23=-Ezcin the above expression.

F渭谓F渭谓=2ExcBx+EycBx+EzcBx+2BzEzc+ByEyc+BxExcF渭谓F渭谓=-2cExBx+EyBy+EzBz-2cExBx+EyBy+EzBzF渭谓F渭谓=-2cE.B-2cE.BF渭谓F渭谓=-4cE.B

Therefore, the tensor invariants areF渭谓F渭谓=2B2-E2c2G渭谓G渭谓=2E2c2-B2andF渭谓G渭谓=4cE.B.

Unlock Step-by-Step Solutions & Ace Your Exams!

  • Full Textbook Solutions

    Get detailed explanations and key concepts

  • Unlimited Al creation

    Al flashcards, explanations, exams and more...

  • Ads-free access

    To over 500 millions flashcards

  • Money-back guarantee

    We refund you if you fail your exam.

Over 30 million students worldwide already upgrade their learning with 91影视!

One App. One Place for Learning.

All the tools & learning materials you need for study success - in one app.

Get started for free

Most popular questions from this chapter

See all solutions

Recommended explanations on Physics Textbooks

View all explanations

What do you think about this solution?

We value your feedback to improve our textbook solutions.

Study anywhere. Anytime. Across all devices.