#boundary of a complex set shaped like a semicircle

42 messages · Page 1 of 1 (latest)

devout sedge
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let S be the set of complex numbers z with magnitude less than R, and with imaginary part greater than 0. does the boundary of S include the values of z such that I(z)=0? (aka, is the “base” of the semicircle part of the boundary)

dusky steppeBOT
magic valve
devout sedge
magic valve
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You should follow your natural instincts

devout sedge
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if it brings about any differences, this boundary is being found to take the integral over the boundary of that set as a contour

devout sedge
magic valve
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wdym

devout sedge
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because i imagine that the contour integral over the boundary with and without that base of the semicircle would have varying answers

devout sedge
# magic valve wdym

when taking the boundary of a complex set such that it plots to. semicircle, is there a convention for whether or not one includes the flat portion of that semicircle in the boundary set

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or would it be simply the curved portion

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to me it seems that one would take it to be the former but it also seems that it would be a bit more convoluted to calculate that set

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this is my exact set

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the complex numbers such that the imaginary part is greater than 0 and the magnitude is between 0 and R exclusive

magic valve
devout sedge
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oh wait

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a boundary must be closed, no?

magic valve
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correct

devout sedge
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so i suppose it would require that the base is included

magic valve
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indeed

devout sedge
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lest the set is not Closed

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okay

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Yay

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well also not yay bc that makes it a bit harder

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but Oh well

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i got my answer. thank u

magic valve
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$\partial X=\overline{X}\setminus X^{\circ}$

muted fulcrumBOT
devout sedge
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what is the circle?

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not familiar with this notation

magic valve
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interior of the set

devout sedge
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Ah

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okay

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i was in fact familiar with that notation

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and forgot

magic valve
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no worries

devout sedge
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thank u for ur help

magic valve
devout sedge
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how do i mark as solved

magic valve
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.solved