In this paper we study a characterization of minimal translation graphs which are generalization of minimal translation hypersurfaces in semi-Euclidean space.
Citation: Derya Sağlam. Minimal translation graphs in semi-Euclidean space[J]. AIMS Mathematics, 2021, 6(9): 10207-10221. doi: 10.3934/math.2021591
[1] | Derya Sağlam . Correction: Minimal translation graphs in semi-Euclidean space. AIMS Mathematics, 2022, 7(5): 9508-9508. doi: 10.3934/math.2022528 |
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In this paper we study a characterization of minimal translation graphs which are generalization of minimal translation hypersurfaces in semi-Euclidean space.
As is wellknown the first non-trivial examples of minimal surfaces in 3-dimensional Euclidean space E3 are the catenoids, the helicoids and the minimal translation surfaces. A surface is called a translation surface if it is given by an immersion
X:U⊂E2→E3,(x,y)→(x,y,z), |
where z=f(x)+g(y). Scherk proved in 1835 that the only minimal translation surfaces (besides the planes) are the surfaces given by
z=1alog|cos(ax)cos(ay)|, |
where a is a non-zero constant [1].
In [2], it has been shown that the minimal translation surfaces are generalized to minimal translation hypersurfaces as follows:
"Let Mn(n≥2) be a translation hypersurface in En+1 i.e. Mn is the graph of a function
F:Rn→R:(x1,…,xn)→F(x1,…,xn)=f1(x1)+⋯+fn(xn), |
where fi is a smooth function of one real variable for i=1,…,n. Then Mn is minimal if and only if either Mn is a hyperplane or a product submanifold Mn=M2×En−2, where M2 is a minimal translation surface of Scherk in E3."
In [3], Woestyne parameterized minimal translation surfaces in the 3-dimensional Minkowski space R31 with metric g=dx21+dx22−dx23, in the following theorems:
Theorem 1. Every minimal, spacelike surface of translation in R31, is congruent to a part of one of the following surfaces:
1. A spacelike plane,
2. The surface of Scherk of the first kind, a parametrization of the surface is F(x,y)=(x,y,a−1log(cosh(ay)/cosh(ax))), with tanh2(ax)+tanh2(ay)<1 [3].
Theorem 2. Every minimal, timelike surface of translation in R31, is congruent to a part of one of the following surfaces:
1. A timelike plane,
2. The surface of Scherk of the first kind, a parametrization of the surface is F(x,y)=(x,y,a−1log(cosh(ay)/cosh(−ax)))with tanh2(−ax)+tanh2(ay)>1.
3. The surface of Scherk of the second kind, a parametrization of the surface is F(x,y)=(x,y,a−1log(cosh(ay)/sinh(−ax))).
4. The surface of Scherk of the third kind, a parametrization of the surface is F(x,y)=(x,y,a−1log(sinh(ay)/sinh(−ax))).
5. A flat B-scroll over a null curve, a parametrization of the surface is F(x,y)=(x,y,±x+g(y))with g(y) an arbitrary function [3].
Seo, gave a classification of the translation hypersurfaces with constant mean curvature or constant Gauss–Kronecker curvature in Euclidean space or Lorentz– Minkowski space in [4]. Also they characterized the minimal translation hypersurfaces in the upper half-space model of hyperbolic space. In particular, they proved the following theorem:
Theorem 3. Let M be a translation hypersurface with constant mean curvature H in Rn+1. Then M is congruent to a cylinder Σ×Rn−2, where Σ is a constant mean curvature surface in R3. In particular, if H=0, then M is either a hyperplane or M=Σ×Rn−2, where Σ is a Scherk's minimal translation surface in R3[4].
And they can obtained a similar result in the Lorentz–Minkowski space as follows:
Theorem 4. Let M be a spacelike translation hypersurface with constant mean curvature H in Ln+1. Then M is congruent to a cylinder Σ×Rn−2, where Σ is a constant mean curvature surface in L3. In particular, if H=0, then M is either a hyperplane or M=Σ×Rn−2, where Σ is a Scherk's maximal spacelike translation surface in L3 [4].
In [5], Hasanis and Lopez classified and described the construction of all minimal translation surfaces in R3. In 2019, Aydın and Ogrenmis investigated translation hypersurfaces generated by translating planar curves and classified these translation hypersurfaces with constant Gauss-Kronecker and mean curvature [6]. Recently, many authors have studied the geometry of minimal translational hypersurface [7,8,9,10,11,12].
In [12], Yang, Zhang and Fu gave a characterization of a class of minimal translation graphs which are generalization of minimal translation hypersurfaces in Euclidean space. In this paper we study a characterization of minimal translation graphs in semi-Euclidean space.
By the (n+1)-dimensional semi-Euclidean space with index ν, denoted by Rn+1ν, mean Rn+1 equipped with the semi-Euclidean metric
g=ε1dx21+ε2dx22+⋯+εn+1dx2n+1, | (2.1) |
for which εi,(i=1,2,…,n+1) is either −1 or 1. We assume n≥2. The number of minus signs is equal to the index ν and is given by
ν=12(n+1−n+1∑j=1εj). |
Let Mn be a hypersurface of Rn+1ν for which the induced metric is non-degenerate. Then Mn can locally always be seen as the graph of a function F:Rn→R. In what follows, we will assume that f is a function of the coordinates x1,…,xn. This can easily be achieved possibly by rearranging the coordinates of Rn+1ν. So Mn is locally given by
xn+1=F(x1,…xn). | (2.2) |
Assume that Mn is minimal. This means that the mean curvature vector vanishes at every point. The graph Mn in the semi-Euclidean space Rnν is minimal if and only if
n∑j=1εj[∂2F∂x2j(n∑i=1εi(∂F∂xi)2+εn+1)−∂F∂xjn∑i=1εi∂F∂xi∂2F∂xi∂xj]=0. | (2.3) |
One easily calculates that minimality condition above [13].
A hypersurface Mn in the semi-Euclidean space Rn+1ν is called translation graph if it is the graph of the function given by
F(x1,…,xn)=f1(x1)+⋯+fn−1(xn−1)+fn(u), |
where u=n∑i=1cixi, ci are constants, cn≠0 and each fi is a smooth function of one real variable for i=1,2,…,n. Additionally in this paper, we assume that the following condition are provided:
n∑i=1εic2i≠0andn∑j=1j≠iεjc2j≠0,foralli=1,…,n−1. | (2.4) |
fi vanishes nowhere for i=1,2,…,n, otherwise Mn is a non-degenerate hyperplane.
The minimality condition (2.3) can be rewritten as
εn+1n∑j=1εjFjj+n∑i≠jεiεj(F2iFjj−FiFjFij)=0. | (2.5) |
Then we calculate the partial derivatives in the Eq (2.5) for the translation graph,
Fi=f′i+cif′n,Fn=cnf′n, | (2.6) |
Fii=f′ii+c2if′′n,Fnn=c2nf′′n, | (2.7) |
Fij=cicjf′′n,Fin=cicnf′′n, | (2.8) |
for 1≤i≤n−1. Since Mn is minimal, we substitute (2.6)–(2.8) into (2.5) and we obtain
εn+1n−1∑i=1εif′′i+(εn+1n∑i=1εic2i+εnc2nn−1∑i=1εif′2i)f′′n+εnc2n(n−1∑i=1εif′′i)f′2n+n−1∑i,j=1i≠jεiεj(f′i+cif′n)2f′′j+12n−1∑i,j=1i≠jεiεj(cif′j−cjf′i)2f′′n=0. | (2.9) |
Since cn≠0, we take the derivative of the Eq (2.9) with respect to xn, we have
[εn+1n∑i=1εic2i+εnc2nn−1∑i=1εif′2i+12n−1∑i,j=1i≠jεiεj(cif′j−cjf′i)2]f′′′n+2[n−1∑i,j=1εi(n∑j=1j≠iεjc2j)f′′i]f′nf′′n+2n−1∑i,j=1i≠jεiεjcif′if′′jf′′n=0. | (2.10) |
According to the Eq (2.10), we get following cases:
Case 1. f′′′n=0.
With proper translation, fn=mu2 for a constant m≠0 such that fn=mu2. If m=0, then Mn would not be a translation graph. According to this, we rewrite (2.10)
2m2un−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i+mn−1∑i,j=1i≠jεiεjcif′if′′j=0. | (2.11) |
Since m≠0, we get
n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i=0,n−1∑i,j=1i≠jεiεjcif′if′′j=0. | (2.12) |
In the first equation of (2.12), each f′′i depends on a different variable, then f′′i has to be a constant for i=1,…,n−1. Also, let be fi(xi)=aix2i, where ai is constant. Then from (2.12) we obtain following equations
n−1∑i=1εi(n∑j=1j≠iεjc2j)ai=0,aicin−1∑j=1j≠iεjaj=0,wherei=1,…,n−1. | (2.13) |
Now we substitute fn=mu2 and fi(xi)=aix2i for i=1,…,n−1 in the Eq (2.9), we find
4m2[n−1∑i=1εi(n∑j=1j≠iεjc2j)ai]u2+8m(n−1∑i,j=1i≠jεiεjaiciajxi)u−4mn−1∑i,j=1i≠jεiεjaiajcicjxixj+4n−1∑i=1εia2i(mn∑j=1j≠iεjc2j+n−1∑j=1j≠iεjaj)x2i+εn+1n−1∑i=1εiai+εn+1mn∑i=1εic2i=0. | (2.14) |
According to (2.13) and (2.14), we obtain
4mn−1∑i,j=1i≠jεiεjaiajcicjxixj=4n−1∑i=1εia2i(mn∑j=1j≠iεjc2j+n−1∑j=1j≠iεjaj)x2i+εn+1n−1∑i=1εiai+εn+1mn∑i=1εic2i | (2.15) |
Since the above equation is a quadratic polynomial with x1,…,xn−1, by the arbitrariness of xi, we get
a2i(mn∑j=1j≠iεjc2j+n−1∑j=1j≠iεjaj)=0,fori=1,…,n−1, | (2.16) |
n−1∑i=1εiai+mn∑i=1εic2i=0 | (2.17) |
and
aiajcicj=0,fori,j=1,…,n−1,i≠j. | (2.18) |
According to (2.16) and (2.17), we find
a3i=−m(ciai)2,fori=1,…,n−1. | (2.19) |
From (2.18), we can see that at most one akck≠0. Without loss of generality, we assume ak0ck0≠0 and every akck=0 for k≠k0. From (2.19), we get ak0≠0 and ak=0 for k≠k0. According to this, with the first equation of (2.13) and the assumption (2.4), we have a contradiction. Therefore, we obtain that every ak=0 for k=1,…,n−1 and f′′i(xi)=0. By substituting this equalities in (2.9) we obtain mn∑i=1εic2i=0, which is a contradiction with the assumption (2.4).
Case 2. f′′′n≠0.
If we divide by f′′′n on both sides of the Eq (2.10), we obtain
[εn+1n∑i=1εic2i+εnc2nn−1∑i=1εif′2i+12n−1∑i,j=1i≠jεiεj(cif′j−cjf′i)2]+2[n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i]f′nf′′nf′′′n+2[n−1∑i,j=1i≠jεiεjcif′if′′j]f′′nf′′′n=0 | (2.20) |
Differentiating (2.20) with respect to u, we get
[n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i](f′nf′′nf′′′n)u+[n−1∑i,j=1i≠jεiεjcif′if′′j](f′′nf′′′n)u=0 | (2.21) |
We have 3 possibilities.
Case 2a. (f′′nf′′′n)u≠0.
In this case,
fn=af′n+bu, | (2.22) |
where a,b are constants. Since f′′′n≠0, then a≠0. By solving this equation we obtain
fn(u)=keua+bu+ab, |
where k is a nonzero constant. According to this equation, we get
(f′nf′′nf′′′n)u=kaeua≠0. |
Thus, according to (2.21), we obtain
n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i=0. | (2.23) |
Since each f′′i depends on a different variable, then f′′i has to be a constant for i=1,…,n−1. Let be fi(xi)=aix2i, where ai is constant. From (2.23) we obtain
n−1∑i=1εi(n∑j=1j≠iεjc2j)ai=0. |
Hence, from (2.20) we have
εn+1n∑i=1εic2i+εnc2nn−1∑i=1εi(2aixi)2+12n−1∑i,j=1i≠jεiεj(2ciajxj−2cjaixi)2+8an−1∑i,j=1i≠jεiεjciaiajxi=0. |
This is a contradiction.
Case 2b. n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i≠0.
Let be n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i=0. Then each f′′i is constant for i=1,…,n−1. Also we can write fi(xi)=aix2i, where ai is constant. From the assumption, we have
n−1∑i=1εi(n∑j=1j≠iεjc2j)ai=0. |
According to (2.21), we get
n−1∑i,j=1i≠jεiεjcif′if′′j=0. |
From (2.20), we obtain
εn+1n∑i=1εic2i+εnc2nn−1∑i=1εi(2aixi)2+12n−1∑i,j=1i≠jεiεj(2ciajxj−2cjaixi)2=0, |
which is a contradiction. Also it must be n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i≠0. According to Cases 2a and 2b, we can rewrite (2.21)
n−1∑i,j=1i≠jεiεjcif′if′′jn−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i=−(f′nf′′nf′′′n)u(f′′nf′′′n)u=m, | (2.24) |
where m is constant. Thus we have
(f′nf′′nf′′′n)u=−m(f′′nf′′′n)u. |
By integration of this equation, we get
f′nf′′nf′′′n=−mf′′nf′′′n+c | (2.25) |
where c is a constant. Thus we have f′nf′′n=−mf′′n+cf′′′n. By integration of this equation, we obtain
f′2n+2mf′n=2cf′′n+c0, | (2.26) |
where c0 is a constant. By solving this ODE, after a translation, we find
fn={−mu−2clncos(√−(m2+c0)2cu),ifm2+c0<0−mu−2clncosh(√m2+c02cu),ifm2+c0>0and|f′n+m√m2+c0|<1−mu−2clnsinh(√m2+c02cu),ifm2+c0>0and|f′n+m√m2+c0|>1−mu−2cln|u|,ifm2+c0=0. |
Moreover, from (2.24), we get
n−1∑i,j=1i≠jεiεjcif′if′′j=mn−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i. | (2.27) |
Since
n−1∑i=1εi(n∑j=1j≠iεjc2j)f′′i≠0, |
all f′′i functions don't vanish for i=1,…,n−1. Let be f′′i0≠0. By differentiating the Eq (2.27) with respect to xi0, we obtain
(mn∑i=1i≠i0εic2i−n−1∑i=1i≠i0εicif′i)f′′′i0f′′i0=ci0n−1∑i=1i≠i0εif′′i. | (2.28) |
Thus we get the following case.
Case 2c. mn∑i=1i≠i0εic2i−n−1∑i=1i≠i0εicif′i=0.
Let be mn∑i=1i≠i0εic2i−n−1∑i=1i≠i0εicif′i≠0. From (2.28), we get
f′′′i0ci0f′′i0=n−1∑i=1i≠i0εif′′imn∑i=1i≠i0εic2i−n−1∑i=1i≠i0εicif′i=a, | (2.29) |
where a is a constant. From (2.29), we obtain
fi0=bi0eaci0xi0−di0aci0xi0, | (2.30) |
where bi0 and di0 are constants. According to (2.29), we get
εi(f′′i+acif′i)=man∑i=1i≠i0εic2i, |
for each i=1,…,i0−1,i0+1,…,n−1. By solving the equation, we obtain
fi=bie−acixi+mn∑i=1i≠i0εic2iεicixi, | (2.31) |
where bi are constants for i=1,…,i0−1,i0+1,…,n−1. By differentiating (2.27) with respect to xk for k=1,…,i0−1,i0+1,…,n−1, we get
f′′′k(n−1∑i=1i≠kεicif′i−mn∑i=1i≠kεic2i)+ckf′′kn−1∑i=1i≠kεif′′i=0. | (2.32) |
We substitute (2.30) and (2.31) in (2.32) and we obtain
2ac3kbkn∑i=1i≠k,i≠i0εic2ibie−a(cixi+ckxk)=c3kbkBke−ackxk, | (2.33) |
where
Bk=(n−3)mn∑i=1i≠i0εic2i−mn∑i=1i≠kεic2i−εi0di0a |
for k=1,…,i0−1,i0+1,…,n−1. Since xk is arbitrary and from (2.31), we get c3kbkc2ibi=0. Hence ckbkcibi=0 for i,k=1,…,i0−1,i0+1,…,n−1 and i≠k. Thus, there is at most one ckbk≠0. Let be all ckbk=0 for k=1,…,i0−1,i0+1,…,n−1 and k≠j0. It follows
f′j0=−abj0cj0e−acj0xj0+mn∑i=1i≠i0εic2iεj0cj0 | (2.34) |
and
f′k=mn∑k=1k≠i0εkc2kεkck | (2.35) |
for k=1,…,i0−1,i0+1,…,n−1 and k≠j0. By substituting (2.30), (2.34) and (2.35) in (2.27), we obtain
εi0(n−3)m(n∑i=1i≠i0εic2i)a2bi0c2i0eaci0xi0+εj0a2bj0c2j0Ce−acj0xj0=0, |
where
C=(n−3)mn∑i=1i≠i0εic2i−mn∑i=1i≠j0εic2i−εi0di0a. |
We rewrite the Eq (2.20) for n=3
ε43∑i=1εic2i+ε3c232∑i=1εif′2i+ε1ε2(c1f′2−c2f′1)2+2[2∑i=1εi(3∑j=1j≠iεjc2j)f′′i]f′3f′′3f′′′3+2[2∑i,j=1i≠jεiεjcif′if′′j]f′′3f′′′3=0. | (2.36) |
According to (2.25) and (2.27), (2.36) becomes
ε4(ε1c21+ε2c22+ε3c23)+ε3c23(ε1f′21+ε2f′22)+ε1ε2(c1f′2−c2f′1)2+2c(ε1(ε2c22+ε3c23)f′′1+ε2(ε1c21+ε3c23)f′′2)=0. | (2.37) |
By differentiating the Eq (2.37) with respect to x1, we obtain
ε3c23f′1f′′1−ε2c2(c1f′2−c2f′1)f′′1+c(ε2c22+ε3c23)f′′′1=0. |
If we arrange the equation above, then we get
(ε2c22+ε3c23)(f′1+cf′′′1f′′1)=ε2c1c2f′2. | (2.38) |
From this equation, f′′2 is constant and f′′2=0. This is a contradiction. Also it must be
mn∑i=1i≠i0εic2i−n−1∑i=1i≠i0εicif′i=0. |
We showed that mn∑i=1i≠i0εic2i−n−1∑i=1i≠i0εicif′i=0 and f′′i are constants for 1≤i≤n−1,i≠i0. Then f′i(xi)=ai, where ai are constants for i=1,…,i0−1,i0+1,…,n−1 and
mn∑i=1i≠i0εic2i=n−1∑i=1i≠i0εiciai | (2.39) |
We rewrite (2.20),
εn+1n∑i=1εic2i+εnc2nn−1∑i=1i≠i0εia2i+εi0f′2i0n∑i=1i≠i0εic2i+n−1∑j=1j≠i0(εja2jn−1∑i=1i≠jεic2i)−2εi0ci0f′i0n−1∑i=1i≠i0εiciai−n−1∑j=1j≠i0(εjcjajn−1∑i=1i≠j,i≠i0εiciai)+2εi0f′′i0(n∑i=1i≠i0εic2i)f′nf′′nf′′′n+2εi0f′′i0(n−1∑i=1i≠i0εiciai)f′′nf′′′n=0 | (2.40) |
According to (2.25) and (2.39), we rewrite (2.40)
εn+1n∑i=1εic2i+εnc2nn−1∑i=1i≠i0εia2i+εi0f′2i0n∑i=1i≠i0εic2i+n−1∑j=1j≠i0(εja2jn−1∑i=1i≠jεic2i)−2εi0ci0f′i0n−1∑i=1i≠i0εiciai−n−1∑j=1j≠i0(εjcjajn−1∑i=1i≠j,i≠i0εiciai)+2εi0cf′′i0n∑i=1i≠i0εic2i=0. | (2.41) |
We arrange this equation
εi0(n∑i=1i≠i0εic2i)f′2i0−2εi0ci0(n−1∑i=1i≠i0εiciai)f′i0+2εi0c(n∑i=1i≠i0εic2i)f′′i0+B=0, | (2.42) |
with
B=εn+1n∑i=1εic2i+εnc2nn−1∑i=1i≠i0εia2i+n−1∑j=1j≠i0(εja2jn−1∑i=1i≠jεic2i)−n−1∑j=1j≠i0(εjcjajn−1∑i=1i≠j,i≠i0εiciai)=εn+1n∑i=1εic2i+(εnc2n+εi0c2i0)n−1∑i=1i≠i0εia2i+12n−1∑i,j=1i≠j,i,j≠i0εiεj(aicj−ajci)2. |
From (2.39), we rewrite (2.42)
f′2i0−2mci0f′i0+2cf′′i0+Bεi0(n∑i=1i≠i0εic2i)=0. |
By solving the equation, we find
fi0={2clncos√−A2cxi0+mci0xi0,ifA<02clncosh√A2cxi0+mci0xi0,ifA>0and|f′i0−mci0√A|<12clnsinh√A2cxi0+mci0xi0,ifA>0and|f′i0−mci0√A|>12cln|xi0|+mci0xi0,ifA=0 | (2.43) |
with
A=Bεi0n∑i=1i≠i0εic2i−m2c2i0. |
Moreover f′i(xi)=ai, where ai are constants for i=1,…,i0−1,i0+1,…,n−1 and we rewrite (2.9) again
[εn+1n∑i=1εic2i+εnc2nn−1∑i=1i≠i0εia2i+εi0f′2i0n∑i=1i≠i0εic2i+n−1∑j=1j≠i0(εja2jn−1∑i=1i≠jεic2i)−2εi0ci0f′i0n−1∑i=1i≠i0εiciai−n−1∑j=1j≠i0(εjcjajn−1∑i=1i≠j,i≠i0εiciai)]f′′n+[εn+1εi0+εi0n−1∑i=1i≠i0εia2i+(εi0n∑i=1i≠i0εic2i)f′2n+2(εi0n−1∑i=1i≠i0εiaici)f′n]f′′i0=0. | (2.44) |
According to (2.41) and (2.44), we get
[εn+1−2c(n∑i=1i≠i0εic2i)f′′n+n−1∑i=1i≠i0εia2i+(n∑i=1i≠i0εic2i)f′2n+2(n−1∑i=1i≠i0εiaici)f′n]f′′i0=0. | (2.45) |
Since f′′i0≠0, by substituting (2.39) into (2.45) and we obtain
f′2n+2mf′n=2cf′′n−εn+1+n−1∑i=1i≠i0εia2in∑i=1i≠i0εic2i. |
When considered this equation with (2.26), then
c0=−εn+1+n−1∑i=1i≠i0εia2in∑i=1i≠i0εic2i. |
According to (2.39), we get
m2+c0=−εn+1n∑i=1i≠i0εic2i−εnc2nn−1∑i=1i≠i0εia2i−[n−1∑i=1i≠i0εia2in−1∑i=1i≠i0εic2i−(n−1∑i=1i≠i0εiciai)2](n∑i=1i≠i0εic2i)2 |
Depending on the epsilones (-1 or +1) in the above equation, m2+c0 can be positive, negative and zero. With suitable translation, we get fi=0 for i=1,…,i0−1,i0+1,…,n−1 and following the equations
fi0={2clncos√−M2cxi0,ifM<02clncosh√M2cxi0,ifM>0and|f′i0√M|<12clnsinh√M2cxi0,ifM>0and|f′i0√M|>12cln|xi0|,ifM=0 | (2.46) |
and
fn={−2clncos(√−N2c(c1x1+⋯+cnxn)),ifN<0−2clncosh(√N2c(c1x1+⋯+cnxn)),ifN>0and|f′n√N|<1−2clnsinh(√N2c(c1x1+⋯+cnxn)),ifN>0and|f′n√N|>1−2cln|c1x1+⋯+cnxn|,ifN=0 | (2.47) |
where
M=εi0εn+1n∑i=1εic2in∑i=1i≠i0εic2i,N=−εn+1n∑i=1i≠i0εic2i. |
Therefore we complete the proof of the following main theorem.
Main theorem. Mn is a non-degenerate minimal translation graph in semi-Euclidean space Rn+1ν, if it is congruent to a part of one of the following surfaces:
1. A non-degenerate hyperplane,
2. A hypersurface parameterized by
ϕ(x1,…,xn)=(x1,…,xn,F(x1,…,xn)),F(x1,…,xn)=fi0(xi0)+fn(u) |
where u=n∑i=1cixi, ci are constants, cn≠0, with the conditions in the Eq (2.4), for a unique i0, 1≤i0≤n−1, such that fi0 and fn one of the previous forms in (2.46) and (2.47), respectively. In additionally, fk(xk)=0 for k≠i0 and 1≤k≤n−1.
Semi-Euclidean spaces are important in applications of general relativity which is the explanation of gravity in modern physics. In this study, we have a characterization of minimal translation graphs which are generalization of minimal translation hypersurfaces in semi-Euclidean space. Also, we obtain the main theorem by which we classify all non-degenerate minimal translation graphs.
The author would like to thank the referees for their valuable suggestions.
The author declares no conflict of interest.
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1. | Derya Sağlam, Correction: Minimal translation graphs in semi-Euclidean space, 2022, 7, 2473-6988, 9508, 10.3934/math.2022528 | |
2. | Derya Sağlam, Minimal homothetical and translation lightlike graphs in Rn+2q, 2022, 7, 2473-6988, 17198, 10.3934/math.2022946 | |
3. | Derya Sağlam, Cumali Sunar, Translation hypersurfaces of semi-Euclidean spaces with constant scalar curvature, 2022, 8, 2473-6988, 5036, 10.3934/math.2023252 |