A Two-Component Generalization of the Integrable rdDym Equation
We find a two-component generalization of the integrable case of rdDym equation. The reductions of this system include the general rdDym equation, the Boyer-Finley equation, and the deformed Boyer-Finley equation. Also we find a Bäcklund transformation between our generalization and Bodganov's...
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irk-123456789-1483872019-02-19T01:24:45Z A Two-Component Generalization of the Integrable rdDym Equation Morozov, O.I. We find a two-component generalization of the integrable case of rdDym equation. The reductions of this system include the general rdDym equation, the Boyer-Finley equation, and the deformed Boyer-Finley equation. Also we find a Bäcklund transformation between our generalization and Bodganov's two-component generalization of the universal hierarchy equation. 2012 Article A Two-Component Generalization of the Integrable rdDym Equation / O.I. Morozov // Symmetry, Integrability and Geometry: Methods and Applications. — 2012. — Т. 8. — Бібліогр.: 26 назв. — англ. 1815-0659 2010 Mathematics Subject Classification: 35A30; 58H05; 58J70 DOI: http://dx.doi.org/10.3842/SIGMA.2012.051 http://dspace.nbuv.gov.ua/handle/123456789/148387 en Symmetry, Integrability and Geometry: Methods and Applications Інститут математики НАН України |
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We find a two-component generalization of the integrable case of rdDym equation. The reductions of this system include the general rdDym equation, the Boyer-Finley equation, and the deformed Boyer-Finley equation. Also we find a Bäcklund transformation between our generalization and Bodganov's two-component generalization of the universal hierarchy equation. |
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Morozov, O.I. A Two-Component Generalization of the Integrable rdDym Equation Symmetry, Integrability and Geometry: Methods and Applications |
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Morozov, O.I. |
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Morozov, O.I. |
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A Two-Component Generalization of the Integrable rdDym Equation |
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A Two-Component Generalization of the Integrable rdDym Equation |
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A Two-Component Generalization of the Integrable rdDym Equation |
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A Two-Component Generalization of the Integrable rdDym Equation |
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A Two-Component Generalization of the Integrable rdDym Equation |
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two-component generalization of the integrable rddym equation |
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Інститут математики НАН України |
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2012 |
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A Two-Component Generalization of the Integrable rdDym Equation / O.I. Morozov // Symmetry, Integrability and Geometry: Methods and Applications. — 2012. — Т. 8. — Бібліогр.: 26 назв. — англ. |
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Symmetry, Integrability and Geometry: Methods and Applications |
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AT morozovoi atwocomponentgeneralizationoftheintegrablerddymequation AT morozovoi twocomponentgeneralizationoftheintegrablerddymequation |
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Symmetry, Integrability and Geometry: Methods and Applications SIGMA 8 (2012), 051, 5 pages
A Two-Component Generalization
of the Integrable rdDym Equation?
Oleg I. MOROZOV
Institute of Mathematics and Statistics, University of Tromsø, Tromsø 90-37, Norway
E-mail: Oleg.Morozov@uit.no
Received May 26, 2012, in final form August 09, 2012; Published online August 11, 2012
http://dx.doi.org/10.3842/SIGMA.2012.051
Abstract. We find a two-component generalization of the integrable case of rdDym equa-
tion. The reductions of this system include the general rdDym equation, the Boyer–Finley
equation, and the deformed Boyer–Finley equation. Also we find a Bäcklund transformation
between our generalization and Bodganov’s two-component generalization of the universal
hierarchy equation.
Key words: coverings of differential equations; Bäcklund transformations
2010 Mathematics Subject Classification: 35A30; 58H05; 58J70
1 Introduction
Recent papers [3, 8, 16] provide two-component generalizations for the hyper-CR Einstein–Weil
structure equation [6, 22]
syy = stx + sysxx − sxsxy, (1.1)
Plebański’s second heavenly equation [25]
sxz = sty + sxxsyy − s2xy (1.2)
and the universal hierarchy equation [18, 19, 22]
sxx = sxsty − stsxy. (1.3)
Namely, equations (1.1)–(1.3) appear from systems
syy = stx + (sy + r)sxx − sxsxy,
ryy = rtx + (sy + r)rxx − sxrxy + r2x;
(1.4)
sxz = sty + sxxsyy − s2xy + r,
rxz = rty + syyrxx + sxxryy − 2sxyrxy,
(1.5)
and
sxx = er(sxsty − stsxy),(
e−r
)
xx
= sxrty − strxy,
(1.6)
respectively, by substituting for r = 0. Other reductions for (1.4) are found in [7, 16]: when
u = 0, system (1.4) gives the Khokhlov–Zabolotskaya (or dispersionless Kadomtsev–Petviashvili)
equation
vyy = vtx + vvxx + v2x,
?This paper is a contribution to the Special Issue “Geometrical Methods in Mathematical Physics”. The full
collection is available at http://www.emis.de/journals/SIGMA/GMMP2012.html
mailto:Oleg.Morozov@uit.no
http://dx.doi.org/10.3842/SIGMA.2012.051
http://www.emis.de/journals/SIGMA/GMMP2012.html
2 O.I. Morozov
while substituting for v = ux in (1.4) produces the normal form
uyy = utx + (ux + uy)uxx − uxuxy,
for the family of equations studied in [7]. Also, we note the reduction v = uy for system (1.4).
This reduction yields equation
uyy = utx − uxuxy
studied in [9, 14, 17, 21].
As it was shown in [3], the reduction s = x for system (1.6) gives the Boyer–Finley equation
rty =
(
e−r
)
xx
. (1.7)
The purpose of the present paper is to introduce the two-component generalization for equa-
tion
uty = uxuxy − uyuxx, (1.8)
which is integrable in the following sense: it has the differential covering [2, 11, 12, 13]
pt = (ux − λ)px, py = λ−1uypx (1.9)
containing the non-removable parameter λ 6= 0 [20]. We show that reductions of the generaliza-
tion include the general r-th dispersionless Dym equation [1]
uty = uxuxy + κuyuxx, (1.10)
the Boyer–Finley equation (1.7), and the deformed Boyer–Finley equation. Also we find a Bäck-
lund transformation between our generalization and Bodganov’s two-component generaliza-
tion (1.6) of the universal hierarchy equation (1.3).
2 The two-component generalization
Along with the covering (1.9) equation (1.8) has the covering
qt = (ux − q)qx, qy = uyq
−1qx, (2.1)
which can be obtained by the method of [20]. While the coverings (1.9) and (2.1) are not
equivalent w.r.t. the pseudo-group of contact transformations, (2.1) can be derived from (1.9)
by the following procedure, see, e.g., [24]. We consider the function p = p(t, x, y) from (1.9) to
be defined implicitly by the equation q(t, x, y, p(t, x, y)) = λ with qp 6= 0. Then for (x1, x2, x3) =
(t, x, y) we have qxi + qppxi = 0, so pxi = −qxi/qp. Substituting these into (1.9) yields (2.1).
Our main observation in this paper is that the covering (2.1) allows the generalization
qt = (ux − q + v)qx + vxq, qy = uyq
−1qx + vy. (2.2)
This system is compatible whenever the two-component system
uty = (ux + v)uxy − uyuxx, (2.3)
vty = (ux + v)vxy − uyvxx + vxvy (2.4)
holds. In other words, (2.2) is a covering for system (2.3), (2.4).
A Two-Component Generalization of the Integrable rdDym Equation 3
3 Reductions
By the construction, we have the following reduction for system (2.2):
Reduction A. Substituting for v = 0 in equations (2.3), (2.2) gives equations (1.8) and (2.1),
while (2.4) becomes an identity.
Also, we have three other reductions.
Reduction B. If we put v = −(κ−1 + 1)ux, then (2.3) gets the form
uty = −κ−1uxuxy − uyuxx, (3.1)
while (2.4) is its differential consequence. The transformation u 7→ −κu maps (3.1) to (1.10).
The corresponding reduction of (2.2) produces the covering of (1.10) studied in [20, 23].
Reduction C. Taking v = −ux in (2.3), (2.4), we obtain
uty = −uyuxx
and its differential consequence. Then we divide this equation by uy, differentiate w.r.t. y and
put uy = −ew. This gives the Boyer–Finley equation [4]
wty = (ew)xx (3.2)
This equation is equation (1.7) in a different notation. Substituting for q = ep in the corre-
sponding reduction of (2.2), we have the covering [10, 15, 26] for equation (3.2):
pt = wt − eppx, py = ew−p(wx − px).
Reduction D. Finally, when we put v = uy − ux into (2.3) and (2.4), we get the equation
uty = uy (uxy − uxx)
and its differential consequence. Then for uy = ew we have the deformed Boyer–Finley equa-
tion [5]
wty = (ew)xy − (ew)xx , (3.3)
and the corresponding reduction of equations (2.2) with q = es gives the covering
st = (es − ew)sx − wt, sy = ew(sx − wx + wy).
for (3.3). This covering in other notations was found in [5, 20].
4 Bäcklund transformations
The substitution
ux = −v +
st
sx
, uy = −e
−r
sx
, vx =
rxst
sx
− rt, vy = −e
−rrx
sx
(4.1)
maps system (2.2) to system
qt =
(
st
sx
− q
)
qx +
(
strx
sx
− rt
)
q, qy = −e
−r
qsx
(qx + rxq) (4.2)
found in [3]. This system is the two-component generalization of the covering
qt =
(
st
sx
− q
)
qx, qy = − qx
qsx
.
4 O.I. Morozov
of equation (1.3). The compatibility conditions for (4.2) coincide with (1.6). Solving (4.1) for
st, sx, rt, rx yields
st = −(ux + v)
e−r
uy
, sx = −e
−r
uy
, rt =
vy
uy
, rx =
(ux + v)vy
uy
− vx. (4.3)
This system is compatible whenever equations (2.3), (2.4) are satisfied. Thus equations (4.1)
define a Bäcklund transformation from (2.3), (2.4) to (1.6) with the inverse transformation (4.3).
In particular, when v = 0 and r = 0, we have a Bäcklund transformation
ux =
st
sx
, uy = − 1
sx
,
between (1.1) and (1.3) with the inverse transformation
st = −ux
uy
, sx = − 1
uy
.
Acknowledgments
I am very grateful to M.V. Pavlov and A.G. Sergyeyev for the valuable discussions. Also I’d
like to thank M. Marvan and A.G. Sergyeyev for the warm hospitality in Mathematical Insti-
tute, Silezian University at Opava, Czech Republic, where this work was initiated and partially
supported by the ESF project CZ.1.07/2.3.00/20.0002.
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1 Introduction
2 The two-component generalization
3 Reductions
4 Bäcklund transformations
References
|