How to evaluate $S=int_partial Dfrac1^2ds(y)$?A Particular Metric: $(mathbbR^2,d_2)$Linear transformation that does thisShow that $int_[0,1]^2g(y_1-y_2) Bbb1_y_1>y_2dy_1dy_2 = int_[0,1]g(m)(1-m), dm$Product metric spaces is again a metric spaceSum of two Dense setsHow do I show that for a multivariate function, Lipschitz continuity in each variable implies Lipschitz continuity for the whole function?Continuity of the inverse mapGiven two real numbers $a$ and $b$ such that $a<b$, what about the convergence of these two sequences?Partial derivative of function with respect to itselfLipschitz property of $f(x,y)= fracxysqrtx^2+y^2$ for $(x,y)neq (0,0)$ and $f(0,0)=0.$
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How to evaluate $S=int_partial Dfrac1x-yds(y)$?
A Particular Metric: $(mathbbR^2,d_2)$Linear transformation that does thisShow that $int_[0,1]^2g(y_1-y_2) Bbb1_y_1>y_2dy_1dy_2 = int_[0,1]g(m)(1-m), dm$Product metric spaces is again a metric spaceSum of two Dense setsHow do I show that for a multivariate function, Lipschitz continuity in each variable implies Lipschitz continuity for the whole function?Continuity of the inverse mapGiven two real numbers $a$ and $b$ such that $a<b$, what about the convergence of these two sequences?Partial derivative of function with respect to itselfLipschitz property of $f(x,y)= fracxysqrtx^2+y^2$ for $(x,y)neq (0,0)$ and $f(0,0)=0.$
$begingroup$
Let $D=B(0,r_0), x,y in mathbbR^3$ and $xin D$.
beginalign*
& S=int_partial Dfrac1x-yds(y)=int_partial Dfrac1(x_1-y_1)^2+(x_2-y_2)^2+(x_3-y_3)^2ds(y)
endalign*
I want to prove that $Sleq k$ ($k>0$ and $k$ only depends on $r_0$).
In case $x ne 0$, my idea is
beginsplit
S^+ &=int_y_1^2+y_2^2leq r_0^2frac1(x_1-y_1)^2+(x_2-y_2)^2+Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2\
&leq int_y_1^2+y_2^2leq r_0^2frac1Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2: text (assume x_3 ne 0)
endsplit
Let $y_1=rcosphi, y_2=rsinphi, 0leq phi leq 2pi$
beginsplit
S^+&=int_0^2pidphiint_0^r_0frac1Big(x_3-sqrtr_0^2-r^2Big)^2fracr_0sqrtr_0^2-r^2rdr\
&=2r_0pileft(frac1-x_3-frac1r_0-x_3right)\
endsplit
with $-r_0<x_3<r_0, x_3 ne 0$, I can't show that $left(frac1-x_3-frac1r_0-x_3right)$ is bounded. Please help me, thank you so much!
real-analysis singular-integrals
$endgroup$
add a comment |
$begingroup$
Let $D=B(0,r_0), x,y in mathbbR^3$ and $xin D$.
beginalign*
& S=int_partial Dfrac1x-yds(y)=int_partial Dfrac1(x_1-y_1)^2+(x_2-y_2)^2+(x_3-y_3)^2ds(y)
endalign*
I want to prove that $Sleq k$ ($k>0$ and $k$ only depends on $r_0$).
In case $x ne 0$, my idea is
beginsplit
S^+ &=int_y_1^2+y_2^2leq r_0^2frac1(x_1-y_1)^2+(x_2-y_2)^2+Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2\
&leq int_y_1^2+y_2^2leq r_0^2frac1Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2: text (assume x_3 ne 0)
endsplit
Let $y_1=rcosphi, y_2=rsinphi, 0leq phi leq 2pi$
beginsplit
S^+&=int_0^2pidphiint_0^r_0frac1Big(x_3-sqrtr_0^2-r^2Big)^2fracr_0sqrtr_0^2-r^2rdr\
&=2r_0pileft(frac1-x_3-frac1r_0-x_3right)\
endsplit
with $-r_0<x_3<r_0, x_3 ne 0$, I can't show that $left(frac1-x_3-frac1r_0-x_3right)$ is bounded. Please help me, thank you so much!
real-analysis singular-integrals
$endgroup$
1
$begingroup$
What has this to do withfunctional-analysis
?
$endgroup$
– José Carlos Santos
yesterday
1
$begingroup$
It's not true... for instance, when $|x-y|to 0$, it explose.
$endgroup$
– user657324
yesterday
$begingroup$
@user657324 since $xin D$ and $y in partial D$ there exists $delta>0$ with $|x-y|>delta$
$endgroup$
– Chloe.Sannon
yesterday
$begingroup$
Yes, but $delta $ depend on $x$, so you can't upper bound $S$ uniformly in $x$. @Chloe.Sannon
$endgroup$
– user657324
yesterday
add a comment |
$begingroup$
Let $D=B(0,r_0), x,y in mathbbR^3$ and $xin D$.
beginalign*
& S=int_partial Dfrac1x-yds(y)=int_partial Dfrac1(x_1-y_1)^2+(x_2-y_2)^2+(x_3-y_3)^2ds(y)
endalign*
I want to prove that $Sleq k$ ($k>0$ and $k$ only depends on $r_0$).
In case $x ne 0$, my idea is
beginsplit
S^+ &=int_y_1^2+y_2^2leq r_0^2frac1(x_1-y_1)^2+(x_2-y_2)^2+Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2\
&leq int_y_1^2+y_2^2leq r_0^2frac1Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2: text (assume x_3 ne 0)
endsplit
Let $y_1=rcosphi, y_2=rsinphi, 0leq phi leq 2pi$
beginsplit
S^+&=int_0^2pidphiint_0^r_0frac1Big(x_3-sqrtr_0^2-r^2Big)^2fracr_0sqrtr_0^2-r^2rdr\
&=2r_0pileft(frac1-x_3-frac1r_0-x_3right)\
endsplit
with $-r_0<x_3<r_0, x_3 ne 0$, I can't show that $left(frac1-x_3-frac1r_0-x_3right)$ is bounded. Please help me, thank you so much!
real-analysis singular-integrals
$endgroup$
Let $D=B(0,r_0), x,y in mathbbR^3$ and $xin D$.
beginalign*
& S=int_partial Dfrac1x-yds(y)=int_partial Dfrac1(x_1-y_1)^2+(x_2-y_2)^2+(x_3-y_3)^2ds(y)
endalign*
I want to prove that $Sleq k$ ($k>0$ and $k$ only depends on $r_0$).
In case $x ne 0$, my idea is
beginsplit
S^+ &=int_y_1^2+y_2^2leq r_0^2frac1(x_1-y_1)^2+(x_2-y_2)^2+Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2\
&leq int_y_1^2+y_2^2leq r_0^2frac1Big(x_3-sqrtr_0^2-y_1^2-y_2^2Big)^2fracr_0sqrtr_0^2-y_1^2-y_2^2dy_1dy_2: text (assume x_3 ne 0)
endsplit
Let $y_1=rcosphi, y_2=rsinphi, 0leq phi leq 2pi$
beginsplit
S^+&=int_0^2pidphiint_0^r_0frac1Big(x_3-sqrtr_0^2-r^2Big)^2fracr_0sqrtr_0^2-r^2rdr\
&=2r_0pileft(frac1-x_3-frac1r_0-x_3right)\
endsplit
with $-r_0<x_3<r_0, x_3 ne 0$, I can't show that $left(frac1-x_3-frac1r_0-x_3right)$ is bounded. Please help me, thank you so much!
real-analysis singular-integrals
real-analysis singular-integrals
edited yesterday
folouer of kaklas
340110
340110
asked yesterday
Chloe.SannonChloe.Sannon
1208
1208
1
$begingroup$
What has this to do withfunctional-analysis
?
$endgroup$
– José Carlos Santos
yesterday
1
$begingroup$
It's not true... for instance, when $|x-y|to 0$, it explose.
$endgroup$
– user657324
yesterday
$begingroup$
@user657324 since $xin D$ and $y in partial D$ there exists $delta>0$ with $|x-y|>delta$
$endgroup$
– Chloe.Sannon
yesterday
$begingroup$
Yes, but $delta $ depend on $x$, so you can't upper bound $S$ uniformly in $x$. @Chloe.Sannon
$endgroup$
– user657324
yesterday
add a comment |
1
$begingroup$
What has this to do withfunctional-analysis
?
$endgroup$
– José Carlos Santos
yesterday
1
$begingroup$
It's not true... for instance, when $|x-y|to 0$, it explose.
$endgroup$
– user657324
yesterday
$begingroup$
@user657324 since $xin D$ and $y in partial D$ there exists $delta>0$ with $|x-y|>delta$
$endgroup$
– Chloe.Sannon
yesterday
$begingroup$
Yes, but $delta $ depend on $x$, so you can't upper bound $S$ uniformly in $x$. @Chloe.Sannon
$endgroup$
– user657324
yesterday
1
1
$begingroup$
What has this to do with
functional-analysis
?$endgroup$
– José Carlos Santos
yesterday
$begingroup$
What has this to do with
functional-analysis
?$endgroup$
– José Carlos Santos
yesterday
1
1
$begingroup$
It's not true... for instance, when $|x-y|to 0$, it explose.
$endgroup$
– user657324
yesterday
$begingroup$
It's not true... for instance, when $|x-y|to 0$, it explose.
$endgroup$
– user657324
yesterday
$begingroup$
@user657324 since $xin D$ and $y in partial D$ there exists $delta>0$ with $|x-y|>delta$
$endgroup$
– Chloe.Sannon
yesterday
$begingroup$
@user657324 since $xin D$ and $y in partial D$ there exists $delta>0$ with $|x-y|>delta$
$endgroup$
– Chloe.Sannon
yesterday
$begingroup$
Yes, but $delta $ depend on $x$, so you can't upper bound $S$ uniformly in $x$. @Chloe.Sannon
$endgroup$
– user657324
yesterday
$begingroup$
Yes, but $delta $ depend on $x$, so you can't upper bound $S$ uniformly in $x$. @Chloe.Sannon
$endgroup$
– user657324
yesterday
add a comment |
2 Answers
2
active
oldest
votes
$begingroup$
You may use spherical coordinates and the cosine-theorem:
$$
frac1x-y = frac1
$$
where $theta_x,y$ is the angle between $x$ and $y$.
Putting it into the integral you have:
$$
intlimits_fracdsx-y =
intlimits_frac r_0^2sin(theta) dphi dthetax=2pi r_0^2intlimits_-1^1frac dcos(theta)x
$$
where we chose to allign $x$ along the z-axis, which we are free to do due to symmetry. Then $theta_x,y$ simply becomes the coordinate $theta$.
$endgroup$
add a comment |
$begingroup$
Clearly,
$$
F(y)=int_fracds^2
$$
is a function of $|y|$. For simplicity, assume that $y=(|y|,0,0)$.
Since the sphere is a solid by revolution, and in particular of revolution of the graph of the function $f(x)=sqrtr^2-x^2$ around the $x-$axis, then
$$
F(y)=2piint_-r_0^r_0 f(x)sqrt1+big(f'(x)big)^2g(x),dx
=cdots=2pi r_0int_-r_0^r_0 g(x),dx
$$
where
$$
g(x)=frac1big(x,sqrtr_0^2-x^2,0big)-(=frac1(x-=frac1r_0^2-2x
$$
and hence
$$
F(y)=2pi r_0int_-r_0^r_0fracdxy=
left.-fraclog(r_0^2+yright|_-r_0^r_0
=fraclogleft(fracyr^2_0-2r_0right)y=
frac
logleft(
fracr_0+y
right)
$$
Clearly,
$$
lim_yF(y)=infty
$$
$endgroup$
add a comment |
Your Answer
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
$begingroup$
You may use spherical coordinates and the cosine-theorem:
$$
frac1x-y = frac1
$$
where $theta_x,y$ is the angle between $x$ and $y$.
Putting it into the integral you have:
$$
intlimits_fracdsx-y =
intlimits_frac r_0^2sin(theta) dphi dthetax=2pi r_0^2intlimits_-1^1frac dcos(theta)x
$$
where we chose to allign $x$ along the z-axis, which we are free to do due to symmetry. Then $theta_x,y$ simply becomes the coordinate $theta$.
$endgroup$
add a comment |
$begingroup$
You may use spherical coordinates and the cosine-theorem:
$$
frac1x-y = frac1
$$
where $theta_x,y$ is the angle between $x$ and $y$.
Putting it into the integral you have:
$$
intlimits_fracdsx-y =
intlimits_frac r_0^2sin(theta) dphi dthetax=2pi r_0^2intlimits_-1^1frac dcos(theta)x
$$
where we chose to allign $x$ along the z-axis, which we are free to do due to symmetry. Then $theta_x,y$ simply becomes the coordinate $theta$.
$endgroup$
add a comment |
$begingroup$
You may use spherical coordinates and the cosine-theorem:
$$
frac1x-y = frac1
$$
where $theta_x,y$ is the angle between $x$ and $y$.
Putting it into the integral you have:
$$
intlimits_fracdsx-y =
intlimits_frac r_0^2sin(theta) dphi dthetax=2pi r_0^2intlimits_-1^1frac dcos(theta)x
$$
where we chose to allign $x$ along the z-axis, which we are free to do due to symmetry. Then $theta_x,y$ simply becomes the coordinate $theta$.
$endgroup$
You may use spherical coordinates and the cosine-theorem:
$$
frac1x-y = frac1
$$
where $theta_x,y$ is the angle between $x$ and $y$.
Putting it into the integral you have:
$$
intlimits_fracdsx-y =
intlimits_frac r_0^2sin(theta) dphi dthetax=2pi r_0^2intlimits_-1^1frac dcos(theta)x
$$
where we chose to allign $x$ along the z-axis, which we are free to do due to symmetry. Then $theta_x,y$ simply becomes the coordinate $theta$.
answered yesterday
denklodenklo
4457
4457
add a comment |
add a comment |
$begingroup$
Clearly,
$$
F(y)=int_fracds^2
$$
is a function of $|y|$. For simplicity, assume that $y=(|y|,0,0)$.
Since the sphere is a solid by revolution, and in particular of revolution of the graph of the function $f(x)=sqrtr^2-x^2$ around the $x-$axis, then
$$
F(y)=2piint_-r_0^r_0 f(x)sqrt1+big(f'(x)big)^2g(x),dx
=cdots=2pi r_0int_-r_0^r_0 g(x),dx
$$
where
$$
g(x)=frac1big(x,sqrtr_0^2-x^2,0big)-(=frac1(x-=frac1r_0^2-2x
$$
and hence
$$
F(y)=2pi r_0int_-r_0^r_0fracdxy=
left.-fraclog(r_0^2+yright|_-r_0^r_0
=fraclogleft(fracyr^2_0-2r_0right)y=
frac
logleft(
fracr_0+y
right)
$$
Clearly,
$$
lim_yF(y)=infty
$$
$endgroup$
add a comment |
$begingroup$
Clearly,
$$
F(y)=int_fracds^2
$$
is a function of $|y|$. For simplicity, assume that $y=(|y|,0,0)$.
Since the sphere is a solid by revolution, and in particular of revolution of the graph of the function $f(x)=sqrtr^2-x^2$ around the $x-$axis, then
$$
F(y)=2piint_-r_0^r_0 f(x)sqrt1+big(f'(x)big)^2g(x),dx
=cdots=2pi r_0int_-r_0^r_0 g(x),dx
$$
where
$$
g(x)=frac1big(x,sqrtr_0^2-x^2,0big)-(=frac1(x-=frac1r_0^2-2x
$$
and hence
$$
F(y)=2pi r_0int_-r_0^r_0fracdxy=
left.-fraclog(r_0^2+yright|_-r_0^r_0
=fraclogleft(fracyr^2_0-2r_0right)y=
frac
logleft(
fracr_0+y
right)
$$
Clearly,
$$
lim_yF(y)=infty
$$
$endgroup$
add a comment |
$begingroup$
Clearly,
$$
F(y)=int_fracds^2
$$
is a function of $|y|$. For simplicity, assume that $y=(|y|,0,0)$.
Since the sphere is a solid by revolution, and in particular of revolution of the graph of the function $f(x)=sqrtr^2-x^2$ around the $x-$axis, then
$$
F(y)=2piint_-r_0^r_0 f(x)sqrt1+big(f'(x)big)^2g(x),dx
=cdots=2pi r_0int_-r_0^r_0 g(x),dx
$$
where
$$
g(x)=frac1big(x,sqrtr_0^2-x^2,0big)-(=frac1(x-=frac1r_0^2-2x
$$
and hence
$$
F(y)=2pi r_0int_-r_0^r_0fracdxy=
left.-fraclog(r_0^2+yright|_-r_0^r_0
=fraclogleft(fracyr^2_0-2r_0right)y=
frac
logleft(
fracr_0+y
right)
$$
Clearly,
$$
lim_yF(y)=infty
$$
$endgroup$
Clearly,
$$
F(y)=int_fracds^2
$$
is a function of $|y|$. For simplicity, assume that $y=(|y|,0,0)$.
Since the sphere is a solid by revolution, and in particular of revolution of the graph of the function $f(x)=sqrtr^2-x^2$ around the $x-$axis, then
$$
F(y)=2piint_-r_0^r_0 f(x)sqrt1+big(f'(x)big)^2g(x),dx
=cdots=2pi r_0int_-r_0^r_0 g(x),dx
$$
where
$$
g(x)=frac1big(x,sqrtr_0^2-x^2,0big)-(=frac1(x-=frac1r_0^2-2x
$$
and hence
$$
F(y)=2pi r_0int_-r_0^r_0fracdxy=
left.-fraclog(r_0^2+yright|_-r_0^r_0
=fraclogleft(fracyr^2_0-2r_0right)y=
frac
logleft(
fracr_0+y
right)
$$
Clearly,
$$
lim_yF(y)=infty
$$
answered yesterday
Yiorgos S. SmyrlisYiorgos S. Smyrlis
63.6k1385165
63.6k1385165
add a comment |
add a comment |
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1
$begingroup$
What has this to do with
functional-analysis
?$endgroup$
– José Carlos Santos
yesterday
1
$begingroup$
It's not true... for instance, when $|x-y|to 0$, it explose.
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– user657324
yesterday
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@user657324 since $xin D$ and $y in partial D$ there exists $delta>0$ with $|x-y|>delta$
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– Chloe.Sannon
yesterday
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Yes, but $delta $ depend on $x$, so you can't upper bound $S$ uniformly in $x$. @Chloe.Sannon
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– user657324
yesterday