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In [[mathematics]], and specifically [[differential geometry]], a '''connection form''' is a manner of organizing the data of a [[connection (mathematics)|connection]] using the language of [[moving frame]]s and [[differential form]]s.


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Historically, connection forms were introduced by [[Élie Cartan]] in the first half of the 20th century as part of, and one of the principal motivations for, his method of moving frames.  The connection form generally depends on a choice of ''frame'', and so is not a [[tensor]]ial object.  Various generalizations and reinterpretations of the connection form were formulated subsequent to Cartan's initial work.  In particular, on a [[principal bundle]], a [[connection (principal bundle)|principal connection]] is a natural reinterpretation of the connection form as a tensorial object.  On the other hand, the connection form has the advantage that it is a differential form defined on the [[differentiable manifold]], rather than on an abstract principal bundle over it.  Hence, despite their lack of tensoriality, connection forms continue to be used because of the relative ease of performing calculations with them.{{harvtxt|Griffiths|Harris|1978}} {{harvtxt|Wells|1980}} {{harvtxt|Spivak|1999}}  In [[physics]], connection forms are also used broadly in the context of [[gauge theory]], through the [[gauge covariant derivative]].
 
A connection form associates to each [[basis of a vector space|basis]] of a [[vector bundle]] a [[matrix (mathematics)|matrix]] of differential forms.  The connection form is not tensorial because under a [[change of basis]], the connection form transforms in a manner that involves the [[exterior derivative]] of the [[Atlas (topology)#Transition maps|transition functions]], in much the same way as the [[Christoffel symbols]] for the [[Levi-Civita connection]].  The main ''tensorial'' invariant of a connection form is its [[curvature form]].  In the presence of a [[solder form]] identifying the vector bundle with the [[tangent bundle]], there is an additional invariant: the [[torsion (differential geometry)|torsion form]].  In many cases, connection forms are considered on vector bundles with additional structure: that of a [[fiber bundle]] with a [[Lie group|structure group]].
 
==Vector bundles==
===Preliminaries===
====Frames on a vector bundle====
Let ''E'' be a [[vector bundle]] of fibre dimension ''k'' over a [[differentiable manifold]] ''M''.  A '''local frame''' for ''E'' is an ordered [[basis of a vector space|basis]] of [[section (fiber bundle)|local sections]] of ''E''.
 
Let '''e'''=(''e''<sub>α</sub>)<sub>α=1,2,...,k</sub> be a local frame on ''E''.  This frame can be used to express locally any section of ''E''.  For suppose that ξ is a local section, defined over the same open set as the frame '''e''', then
:<math>\xi = \sum_{\alpha=1}^k e_\alpha \xi^\alpha(\mathbf e)</math>
where ξ<sup>α</sup>('''e''') denotes the ''components'' of ξ in the frame '''e'''.  As a matrix equation, this reads
:<math>\xi = {\mathbf e}
\begin{bmatrix}
\xi^1(\mathbf e)\\
\xi^2(\mathbf e)\\
\vdots\\
\xi^k(\mathbf e)
\end{bmatrix}=
{\mathbf e}\, \xi(\mathbf e)
</math>
 
====Exterior connections====
{{see also|Exterior covariant derivative}}
A [[connection (vector bundle)|connection]] in ''E'' is a type of [[differential operator]]
:<math>D : \Gamma(E) \rightarrow \Gamma(E\otimes\Omega^1M)</math>
where Γ denotes the [[sheaf (mathematics)|sheaf]] of local [[section (fibre bundle)|sections]] of a vector bundle, and Ω<sup>1</sup>''M'' is the bundle of differential 1-forms on ''M''.  For ''D'' to be a connection, it must be correctly coupled to the [[exterior derivative]].  Specifically, if ''v'' is a local section of ''E'', and ''f'' is a smooth function, then
:<math>D(fv) = v\otimes (df) + fDv</math>
where ''df'' is the exterior derivative of ''f''.
 
Sometimes it is convenient to extend the definition of ''D'' to arbitrary [[vector-valued differential form|''E''-valued forms]], thus regarding it as a differential operator on the tensor product of ''E'' with the full [[exterior algebra]] of differential forms.  Given an exterior connection ''D'' satisfying this compatibility property, there exists a unique extension of ''D'':
:<math>D : \Gamma(E\otimes\Omega^*M) \rightarrow \Gamma(E\otimes\Omega^*M)</math>
such that
:<math> D(v\wedge\alpha) = (Dv)\wedge\alpha + (-1)^{\text{deg}\, v}v\wedge d\alpha</math>
where ''v'' is homogeneous of degree deg ''v''.  In other words, ''D'' is a [[derivation (abstract algebra)|derivation]] on the sheaf of graded modules Γ(''E'' ⊗ Ω<sup>*</sup>''M'').
 
===Connection forms===
The '''connection form''' arises when applying the exterior connection to a particular frame '''e'''.  Upon applying the exterior connection to the ''e''<sub>α</sub>, it is the unique ''k'' &times; ''k'' matrix (ω<sub>α</sub><sup>β</sup>) of [[one-form]]s on ''M'' such that
:<math>D e_\alpha = \sum_{\beta=1}^k e_\beta\otimes\omega^\beta_\alpha.</math>
In terms of the connection form, the exterior connection of any section of ''E'' can now be expressed, for suppose that ξ = Σ<sub>α</sub> e<sub>α</sub>ξ<sup>α</sup>.  Then
:<math>D\xi = \sum_{\alpha=1}^k D(e_\alpha\xi^\alpha(\mathbf e)) = \sum_{\alpha=1}^k e_\alpha\otimes d\xi^\alpha(\mathbf e) + \sum_{\alpha=1}^k\sum_{\beta=1}^k e_\beta\otimes\omega^\beta_\alpha \xi^\alpha(\mathbf e).</math>
 
Taking components on both sides,
:<math>D\xi(\mathbf e) = d\xi(\mathbf e)+\omega \xi(\mathbf e) = (d+\omega)\xi(\mathbf e)</math>
where it is understood that ''d'' and ω refer to the exterior derivative and a matrix of 1-forms, respectively, acting on the components of ξ.  Conversely, a matrix of 1-forms ω is ''a priori'' sufficient to completely determine the connection locally on the open set over which the basis of sections '''e''' is defined.
 
====Change of frame====
In order to extend ω to a suitable global object, it is necessary to examine how it behaves when a different choice of basic sections of ''E'' is chosen.  Write ω<sub>α</sub><sup>β</sup> = ω<sub>α</sub><sup>β</sup>('''e''') to indicate the dependence on the choice of '''e'''.
 
Suppose that '''e'''&prime; is a different choice of local basis.  Then there is an invertible ''k'' &times; ''k'' matrix of functions ''g'' such that
:<math>{\mathbf e}' = {\mathbf e}\, g,\quad \text{i.e., }\,e'_\alpha = \sum_\beta e_\beta g^\beta_\alpha.</math>
Applying the exterior connection to both sides gives the transformation law for ω:
:<math>\omega(\mathbf e\, g) = g^{-1}dg+g^{-1}\omega(\mathbf e)g.</math>
Note in particular that ω fails to transform in a [[tensor]]ial manner, since the rule for passing from one frame to another involves the derivatives of the transition matrix ''g''.
 
====Global connection forms====
If {''U''<sub>p</sup>} is an open covering of ''M'', and each ''U''<sub>p</sub> is equipped with a trivialization '''e'''<sub>p</sub> of ''E'', then it is possible to define a global connection form in terms of the patching data between the local connection forms on the overlap regions.  In detail, a '''connection form''' on ''M'' is a system of matrices ω('''e'''<sub>p</sub>) of 1-forms defined on each ''U''<sub>p</sub> that satisfy the following compatibility condition
:<math>\omega(\mathbf e_q) = (\mathbf e_p^{-1}\mathbf e_q)^{-1}d(\mathbf e_p^{-1}\mathbf e_q)+(\mathbf e_p^{-1}\mathbf e_q)^{-1}\omega(\mathbf e_p)(\mathbf e_p^{-1}\mathbf e_q).</math>
This ''compatibility condition'' ensures in particular that the exterior connection of a section of ''E'', when regarded abstractly as a section of ''E'' ⊗ Ω<sup>1</sup>''M'', does not depend on the choice of basis section used to define the connection.
 
===Curvature===
The '''curvature two-form''' of a connection form in ''E'' is defined by
:<math>\Omega(\mathbf e) = d\omega(\mathbf e) + \omega(\mathbf e)\wedge\omega(\mathbf e).</math>
Unlike the connection form, the curvature behaves tensorially under a change of frame, which can be checked directly by using the [[Poincaré lemma]]. Specifically, if '''e''' → '''e''' ''g'' is a change of frame, then the curvature two-form transforms by
:<math>\Omega(\mathbf e\, g) = g^{-1}\Omega(\mathbf e)g.</math>
One interpretation of this transformation law is as follows.  Let '''e'''<sup>*</sup> be the [[dual basis]] corresponding to the frame ''e''.  Then the 2-form
:<math>\Omega={\mathbf e}\Omega(\mathbf e){\mathbf e}^*</math>
is independent of the choice of frame.  In particular, Ω is a vector-valued two-form on ''M'' with values in the [[endomorphism ring]] Hom(''E'',''E'').  Symbolically,
:<math>\Omega\in \Gamma(\Omega^2M\otimes \text{Hom}(E,E)).</math>
 
In terms of the exterior connection ''D'', the curvature endomorphism is given by
:<math>\Omega(v) = D(D v) = D^2v\, </math>
for ''v'' ∈ ''E''. Thus the curvature measures the failure of the sequence
:<math>\Gamma(E)\ \stackrel{D}{\to}\ \Gamma(E\otimes\Omega^1M)\ \stackrel{D}{\to}\ \Gamma(E\otimes\Omega^2M)\ \stackrel{D}{\to}\ \dots\ \stackrel{D}{\to}\ \Gamma(E\otimes\Omega^n(M))</math>
to be a [[chain complex]] (in the sense of [[de Rham cohomology]]).
 
===Soldering and torsion===
Suppose that the fibre dimension ''k'' of ''E'' is equal to the dimension of the manifold ''M''.  In this case, the vector bundle ''E'' is sometimes equipped with an additional piece of data besides its connection: a [[solder form]]. A '''solder form''' is a globally defined [[vector-valued form|vector-valued one-form]] θ ∈ Γ(Ω<sup>1</sup>(''M'',''E'')) such that the mapping
:<math>\theta_x : T_xM \rightarrow E_x</math>
is a linear isomorphism for all ''x'' ∈ ''M''.  If a solder form is given, then it is possible to define the '''[[torsion (differential geometry)|torsion]]''' of the connection (in terms of the exterior connection) as
:<math>\Theta = D\theta.\, </math>
The torsion Θ is an ''E''-valued 2-form on ''M''.
 
A solder form and the associated torsion may both be described in terms of a local frame '''e''' of ''E''. If θ is a solder form, then it decomposes into the frame components
:<math>\theta = \sum_i \theta^i(\mathbf e) e_i.</math>
The components of the torsion are then
:<math>\Theta^i(\mathbf e) = d\theta^i(\mathbf e) + \sum_j \omega_j^i(\mathbf e)\wedge \theta^j(\mathbf e).</math>
Much like the curvature, it can be shown that Θ behaves as a [[Covariance and contravariance of vectors|contravariant tensor]] under a change in frame:
:<math>\Theta^i(\mathbf e\, g)=\sum_j g_j^i \Theta^j(\mathbf e).</math>
 
The frame-independent torsion may also be recovered from the frame components:
:<math>\Theta = \sum_i e_i \Theta^i(\mathbf e).</math>
 
===Example: The Levi-Civita connection===
As an example, suppose that ''M'' carries a [[Riemannian metric]], and consider the [[Levi-Civita connection]] on the [[tangent bundle]] of ''M''.<ref>See {{harvtxt|Spivak|1999}}, II.7 for a complete account of the Levi-Civita connection from this point of view.</ref>  A local frame on the tangent bundle is an ordered list of vector fields '''e''' = (''e''<sub>i</sub> | i = 1,2,...,n=dim ''M'') defined on an open subset of ''M'' that are linearly independent at every point of their domain.  The Christoffel symbols define the Levi-Civita connection by
:<math>\nabla_{e_i}e_j = \sum_{k=1}^n\Gamma_{ij}^k(\mathbf e)e_k.</math>
If θ = (θ<sub>i</sub> | i=1,2,...,n), denotes the [[dual basis]] of the [[cotangent bundle]], such that θ<sub>i</sub>(''e''<sub>j</sub>) = δ<sub>ij</sub> (the [[Kronecker delta]]), then the connection form is
:<math>\omega_i^j(\mathbf e) = \sum_k \Gamma_{ki}^j(\mathbf e)\theta^k.</math>
 
In terms of the connection form, the exterior connection on a vector field ''v'' = Σ<sub>i</sub>''e''<sub>i</sub>''v''<sup>i</sup> is given by
:<math> Dv=\sum_k e_k\otimes(dv^k) + \sum_{j,k}e_k\otimes\omega^k_j(\mathbf e)v^j.</math>
One can recover the Levi-Civita connection, in the usual sense, from this by contracting with ''e''<sub>i</sub>:
:<math> \nabla_{e_i} v = \langle Dv, e_i\rangle = \sum_k e_k \left(\nabla_{e_i} v^k + \Sigma_j\Gamma^k_{ij}(\mathbf e)v^j\right)</math>
 
====Curvature====
The curvature 2-form of the Levi-Civita connection is the matrix (Ω<sub>i</sub><sup>j</sup>) given by
:<math>
\Omega_i^j(\mathbf e) = d\omega_i^j(\mathbf e)+\sum_k\omega_k^j(\mathbf e)\wedge\omega_i^k(\mathbf e).
</math>
For simplicity, suppose that the frame '''e''' is [[Holonomic basis|holonomic]], so that dθ<sup>i</sup>=0.<ref>In a non-holonomic frame, the expression of curvature is further complicated by the fact that the derivatives dθ<sup>i</sup> must be taken into account.</ref>  Then, employing now the [[summation convention]] on repeated indices,
:<math>\begin{array}{ll}
\Omega_i^j &= d(\Gamma^j_{qi}\theta^q) + (\Gamma^j_{pk}\theta^p)\wedge(\Gamma^k_{qi}\theta^q)\\
&\\
&=\theta^p\wedge\theta^q\left(\partial_p\Gamma^j_{qi}+\Gamma^j_{pk}\Gamma^k_{qi})\right)\\
&\\
&=\tfrac12\theta^p\wedge\theta^q R_{pqi}{}^j
\end{array}
</math>
where ''R'' is the [[Riemann curvature tensor]].
 
====Torsion====
The Levi-Civita connection is characterized as the unique [[metric connection]] in the tangent bundle with zero torsion.  To describe the torsion, note that the vector bundle ''E'' is the tangent bundle.  This carries a canonical solder form (sometimes called the '''canonical one-form''') that is the section θ of Hom(T''M'',T''M'') = T<sup>*</sup>''M'' ⊗ T''M'' corresponding to the identity endomorphism of the tangent spaces.  In the frame '''e''', the solder form is θ = Σ<sub>i</sub> ''e''<sub>i</sub> ⊗ θ<sup>i</sup>, where again θ<sup>i</sup> is the dual basis.
 
The torsion of the connection is given by Θ = ''D'' θ, or in terms of the frame components of the solder form by
:<math>\Theta^i(\mathbf e) = d\theta^i+\sum_j\omega^i_j(\mathbf e)\wedge\theta^j.</math>
Assuming again for simplicity that '''e''' is holonomic, this expression reduces to
:<math>\Theta^i = \Gamma^i_{kj} \theta^k\wedge\theta^j</math>,
which vanishes if and only if Γ<sup>i</sup><sub>kj</sub> is symmetric on its lower indices.
 
==Structure groups==
A more specific type of connection form can be constructed when the vector bundle ''E'' carries a [[associated bundle|structure group]].  This amounts to a preferred class of frames '''e''' on ''E'', which are related by a [[Lie group]] ''G''.  For example, in the presence of a [[metric (vector bundle)|metric]] in ''E'', one works with frames that form an [[orthonormal basis]] at each point. The structure group is then the [[orthogonal group]], since this group preserves the orthonormality of frames.  Other examples include:
* The usual frames, considered in the preceding section, have structural group GL(''k'') where ''k'' is the fibre dimension of ''E''.
* The holomorphic tangent bundle of a [[complex manifold]] (or [[almost complex manifold]]).<ref>Wells (1973).</ref>  Here the structure group is GL<sub>n</sub>('''C''') ⊂ GL<sub>2n</sub>('''R''').<ref>See for instance Kobayashi and Nomizu, Volume II.</ref>  In case a [[hermitian metric]] is given, then the structure group reduces to the [[unitary group]] acting on unitary frames.<ref>Wells, ''ibid''.</ref>
* [[Spinor]]s on a manifold equipped with a [[spin structure]].  The frames are unitary with respect to an invariant inner product on the spin space, and the group reduces to the [[spin group]].
* Holomorphic tangent bundles on [[CR manifold]]s.<ref>See Chern and Moser.</ref>
 
In general, let ''E'' be a given vector bundle of fibre dimension ''k'' and ''G'' ⊂ GL(''k'') a given Lie subgroup of the general linear group of '''R'''<sup>k</sup>. If (''e''<sub>α</sub>) is a local frame of ''E'', then a matrix-valued function (''g''<sub>i</sub></sup>j</sup>): ''M'' → ''G'' may act on the ''e''<sub>α</sub> to produce a new frame
:<math>e_\alpha' = \sum_\beta e_\beta g_\alpha^\beta.</math>
Two such frames are '''''G''-related'''.  Informally, the vector bundle ''E'' has the '''structure of a ''G''-bundle''' if a preferred class of frames is specified, all of which are locally ''G''-related to each other.  In formal terms, ''E'' is a [[fibre bundle]] with structure group ''G'' whose typical fibre is '''R'''<sup>k</sup> with the natural action of ''G'' as a subgroup of GL(''k'').
 
===Compatible connections===
A connection is [[metric compatible|compatible]] with the structure of a ''G''-bundle on ''E'' provided that the associated [[parallel transport]] maps always send one ''G''-frame to another.  Formally, along a curve γ, the following must hold locally (that is, for sufficiently small values of ''t''):
:<math>\Gamma(\gamma)_0^t e_\alpha(\gamma(0)) = \sum_\beta e_\beta(\gamma(t))g_\alpha^\beta(t) </math>
for some matrix ''g''<sub>α</sub><sup>β</sup> (which may also depend on ''t'').  Differentiation at ''t''=0 gives
:<math>\nabla_{\dot{\gamma}(0)} e_\alpha = \sum_\beta e_\beta \omega_\alpha^\beta(\dot{\gamma}(0))</math>
where the coefficients ω<sub>α</sub><sup>β</sup> are in the [[Lie algebra]] '''g''' of the Lie group ''G''.
 
With this observation, the connection form ω<sub>α</sub><sup>β</sup> defined by
:<math>D e_\alpha = \sum_\beta e_\beta\otimes \omega_\alpha^\beta(\mathbf e)</math>
is '''compatible with the structure''' if the matrix of one-forms ω<sub>α</sub><sup>β</sup>('''e''') takes its values in '''g'''.
 
The curvature form of a compatible connection is, moreover, a '''g'''-valued two-form.
 
===Change of frame===
Under a change of frame
:<math>e_\alpha' = \sum_\beta e_\beta g_\alpha^\beta</math>
where ''g'' is a ''G''-valued function defined on an open subset of ''M'', the connection form transforms via <!--Todo: incorporate index version above as well. -->
:<math>\omega_\alpha^\beta(\mathbf e\cdot g) = (g^{-1})_\gamma^\beta dg_\alpha^\gamma + (g^{-1})_\gamma^\beta \omega_\delta^\gamma(\mathbf e)g_\alpha^\delta.</math>
Or, using matrix products:
:<math>\omega({\mathbf e}\cdot g) = g^{-1}dg + g^{-1}\omega g.</math>
To interpret each of these terms, recall that ''g'' : ''M'' → ''G'' is a ''G''-valued (locally defined) function. With this in mind,
:<math>\omega({\mathbf e}\cdot g) = g^*\omega_{\mathfrak g} + \text{Ad}_{g^{-1}}\omega(\mathbf e)</math>
where ω<sub>'''g'''</sub> is the [[Maurer-Cartan form]] for the group ''G'', here [[pullback (differential geometry)|pulled back]] to ''M'' along the function ''g'', and Ad is the [[adjoint representation]] of ''G'' on its Lie algebra.
 
==Principal bundles==
The connection form, as introduced thus far, depends on a particular choice of frame.  In the first definition, the frame is just a local basis of sections.  To each frame, a connection form is given with a transformation law for passing from one frame to another. In the second definition, the frames themselves carry some additional structure provided by a Lie group, and changes of frame are constrained to those that take their values in it. The language of principal bundles, pioneered by [[Charles Ehresmann]] in the 1940s, provides a manner of organizing these many connection forms and the transformation laws connecting them into a single intrinsic form with a single rule for transformation. The disadvantage to this approach is that the forms are no longer defined on the manifold itself, but rather on a larger principal bundle.
 
===The principal connection for a connection form===
Suppose that ''E'' → ''M'' is a vector bundle with structure group ''G''. Let {''U''} be an open cover of ''M'', along with ''G''-frames on each ''U'', denoted by '''e'''<sub>U</sub>.  These are related on the intersections of overlapping open sets by
:<math>{\mathbf e}_V={\mathbf e}_U\cdot h_{UV}</math>
for some ''G''-valued function ''h''<sub>UV</sup> defined on ''U'' ∩ ''V''.
 
Let F<sub>G</sub>''E'' be the set of all ''G''-frames taken over each point of ''M''.  This is a principal ''G''-bundle over ''M''.  In detail, using the fact that the ''G''-frames are all ''G''-related, F<sub>G</sub>''E'' can be realized in terms of gluing data among the sets of the open cover:
:<math>F_GE = \left.\coprod_U U\times G\right/\sim</math>
where the [[equivalence relation]] <math>\sim</math> is defined by
:<math>((x,g_U)\in U\times G) \sim ((x,g_V) \in V\times G) \iff {\mathbf e}_V={\mathbf e}_U\cdot h_{UV} \text{ and } g_U = h_{UV}^{-1}(x) g_V. </math>
 
On F<sub>G</sub>''E'', define a [[connection (principal bundle)|principal ''G''-connection]] as follows, by specifying a '''g'''-valued one-form on each product ''U'' &times; ''G'', which respects the equivalence relation on the overlap regions.  First let
:<math>\pi_1:U\times G \to U,\quad \pi_2 : U\times G \to G</math>
be the projection maps.  Now, for a point (''x'',''g'') ∈ ''U'' &times; ''G'', set
:<math>\omega_{(x,g)} = Ad_{g^{-1}}\pi_1^*\omega(\mathbf e_U)+\pi_2^*\omega_{\mathbf g}.</math>
The 1-form ω constructed in this way respects the transitions between overlapping sets, and therefore descends to give a globally defined 1-form on the principal bundle F<sub>G</sub>''E''. It can be shown that ω is a principal connection in the sense that it reproduces the generators of the right ''G'' action on F<sub>G</sub>''E'', and equivariantly intertwines the right action on T(F<sub>G</sub>''E'') with the adjoint representation of ''G''.
 
===Connection forms associated to a principal connection===
Conversely, a principal ''G''-connection ω in a principal ''G''-bundle ''P''→''M'' gives rise to a collection of connection forms on ''M''.  Suppose that '''e''' : ''M'' → ''P'' is a local section of ''P''.  Then the pullback of ω along '''e''' defines a '''g'''-valued one-form on ''M'':
:<math>\omega({\mathbf e}) = {\mathbf e}^*\omega.</math>
Changing frames by a ''G''-valued function ''g'', one sees that ω('''e''') transforms in the required manner by using the Leibniz rule, and the adjunction:
:<math>\langle X, ({\mathbf e}\cdot g)^*\omega\rangle = \langle [d(\mathbf e\cdot g)](X), \omega\rangle</math>
where ''X'' is a vector on ''M'', and ''d'' denotes the [[pushforward (differential)|pushforward]].
 
==See also==
* [[Ehresmann connection]]
* [[Cartan connection]]
* [[Affine connection]]
* [[Curvature form]]
 
==Notes==
<references/>
 
==References==
* Chern, S.-S., ''Topics in Differential Geometry'', Institute for Advanced Study, mimeographed lecture notes, 1951.
 
* {{citation|author=Chern S. S. and Moser, J.K.|title=Real hypersurfaces in complex manifolds|journal=Acta Math.|volume=133|pages=219–271|year=1974|doi=10.1007/BF02392146}}
 
* {{citation| last1=Griffiths | first1=Phillip | last2=Harris | first2=Joseph |author-link1=Phillip Griffiths |author-link2=Joseph Harris |title=Principles of algebraic geometry|isbn=0-471-05059-8|year=1978|publisher=John Wiley and sons}}
 
* {{citation | author=Kobayashi, Shoshichi and Nomizu, Katsumi | title = [[Foundations of Differential Geometry]], Vol. 1 | publisher=Wiley-Interscience | year=1996 (New edition) |isbn = 0-471-15733-3}}
 
* {{citation | author=Kobayashi, Shoshichi and Nomizu, Katsumi | title = Foundations of Differential Geometry, Vol. 2 | publisher=Wiley-Interscience | year=1996 (New edition) |isbn = 0-471-15732-5}}
 
* {{citation|last=Spivak|first=Michael|title=A Comprehensive introduction to differential geometry (Volume 2)|year=1999|publisher=Publish or Perish|isbn=0-914098-71-3}}
 
* {{citation|last=Spivak|first=Michael|title=A Comprehensive introduction to differential geometry (Volume 3)|year=1999|publisher=Publish or Perish|isbn=0-914098-72-1}}
 
* {{citation|last=Wells|first=R.O.|authorlink=Raymond O. Wells, Jr.|title=Differential analysis on complex manifolds|year=1973|publisher=Springer-Verlag|isbn=0-387-90419-0}}
 
* {{citation|last=Wells|first=R.O.|authorlink=Raymond O. Wells, Jr.|title=Differential analysis on complex manifolds|year=1980|publisher=Prentice–Hall }}
 
{{Tensors}}
 
[[Category:Differential geometry]]
[[Category:Fiber bundles]]
[[Category:Connection (mathematics)]]

Revision as of 17:23, 20 October 2013

In mathematics, and specifically differential geometry, a connection form is a manner of organizing the data of a connection using the language of moving frames and differential forms.

Historically, connection forms were introduced by Élie Cartan in the first half of the 20th century as part of, and one of the principal motivations for, his method of moving frames. The connection form generally depends on a choice of frame, and so is not a tensorial object. Various generalizations and reinterpretations of the connection form were formulated subsequent to Cartan's initial work. In particular, on a principal bundle, a principal connection is a natural reinterpretation of the connection form as a tensorial object. On the other hand, the connection form has the advantage that it is a differential form defined on the differentiable manifold, rather than on an abstract principal bundle over it. Hence, despite their lack of tensoriality, connection forms continue to be used because of the relative ease of performing calculations with them.Template:Harvtxt Template:Harvtxt Template:Harvtxt In physics, connection forms are also used broadly in the context of gauge theory, through the gauge covariant derivative.

A connection form associates to each basis of a vector bundle a matrix of differential forms. The connection form is not tensorial because under a change of basis, the connection form transforms in a manner that involves the exterior derivative of the transition functions, in much the same way as the Christoffel symbols for the Levi-Civita connection. The main tensorial invariant of a connection form is its curvature form. In the presence of a solder form identifying the vector bundle with the tangent bundle, there is an additional invariant: the torsion form. In many cases, connection forms are considered on vector bundles with additional structure: that of a fiber bundle with a structure group.

Vector bundles

Preliminaries

Frames on a vector bundle

Let E be a vector bundle of fibre dimension k over a differentiable manifold M. A local frame for E is an ordered basis of local sections of E.

Let e=(eα)α=1,2,...,k be a local frame on E. This frame can be used to express locally any section of E. For suppose that ξ is a local section, defined over the same open set as the frame e, then

where ξα(e) denotes the components of ξ in the frame e. As a matrix equation, this reads

Exterior connections

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In 12 months 2013, c ommercial retails, shoebox residences and mass market properties continued to be the celebrities of the property market. Models are snapped up in report time and at document breaking prices. Builders are having fun with overwhelming demand and patrons need more. We feel that these segments of the property market are booming is a repercussion of the property cooling measures no.6 and no. 7. With additional buyer's stamp responsibility imposed on residential properties, buyers change their focus to commercial and industrial properties. I imagine every property purchasers need their property funding to understand in value. A connection in E is a type of differential operator

where Γ denotes the sheaf of local sections of a vector bundle, and Ω1M is the bundle of differential 1-forms on M. For D to be a connection, it must be correctly coupled to the exterior derivative. Specifically, if v is a local section of E, and f is a smooth function, then

where df is the exterior derivative of f.

Sometimes it is convenient to extend the definition of D to arbitrary E-valued forms, thus regarding it as a differential operator on the tensor product of E with the full exterior algebra of differential forms. Given an exterior connection D satisfying this compatibility property, there exists a unique extension of D:

such that

where v is homogeneous of degree deg v. In other words, D is a derivation on the sheaf of graded modules Γ(E ⊗ Ω*M).

Connection forms

The connection form arises when applying the exterior connection to a particular frame e. Upon applying the exterior connection to the eα, it is the unique k × k matrix (ωαβ) of one-forms on M such that

In terms of the connection form, the exterior connection of any section of E can now be expressed, for suppose that ξ = Σα eαξα. Then

Taking components on both sides,

where it is understood that d and ω refer to the exterior derivative and a matrix of 1-forms, respectively, acting on the components of ξ. Conversely, a matrix of 1-forms ω is a priori sufficient to completely determine the connection locally on the open set over which the basis of sections e is defined.

Change of frame

In order to extend ω to a suitable global object, it is necessary to examine how it behaves when a different choice of basic sections of E is chosen. Write ωαβ = ωαβ(e) to indicate the dependence on the choice of e.

Suppose that e′ is a different choice of local basis. Then there is an invertible k × k matrix of functions g such that

Applying the exterior connection to both sides gives the transformation law for ω:

Note in particular that ω fails to transform in a tensorial manner, since the rule for passing from one frame to another involves the derivatives of the transition matrix g.

Global connection forms

If {Up} is an open covering of M, and each Up is equipped with a trivialization ep of E, then it is possible to define a global connection form in terms of the patching data between the local connection forms on the overlap regions. In detail, a connection form on M is a system of matrices ω(ep) of 1-forms defined on each Up that satisfy the following compatibility condition

This compatibility condition ensures in particular that the exterior connection of a section of E, when regarded abstractly as a section of E ⊗ Ω1M, does not depend on the choice of basis section used to define the connection.

Curvature

The curvature two-form of a connection form in E is defined by

Unlike the connection form, the curvature behaves tensorially under a change of frame, which can be checked directly by using the Poincaré lemma. Specifically, if ee g is a change of frame, then the curvature two-form transforms by

One interpretation of this transformation law is as follows. Let e* be the dual basis corresponding to the frame e. Then the 2-form

is independent of the choice of frame. In particular, Ω is a vector-valued two-form on M with values in the endomorphism ring Hom(E,E). Symbolically,

In terms of the exterior connection D, the curvature endomorphism is given by

for vE. Thus the curvature measures the failure of the sequence

to be a chain complex (in the sense of de Rham cohomology).

Soldering and torsion

Suppose that the fibre dimension k of E is equal to the dimension of the manifold M. In this case, the vector bundle E is sometimes equipped with an additional piece of data besides its connection: a solder form. A solder form is a globally defined vector-valued one-form θ ∈ Γ(Ω1(M,E)) such that the mapping

is a linear isomorphism for all xM. If a solder form is given, then it is possible to define the torsion of the connection (in terms of the exterior connection) as

The torsion Θ is an E-valued 2-form on M.

A solder form and the associated torsion may both be described in terms of a local frame e of E. If θ is a solder form, then it decomposes into the frame components

The components of the torsion are then

Much like the curvature, it can be shown that Θ behaves as a contravariant tensor under a change in frame:

The frame-independent torsion may also be recovered from the frame components:

Example: The Levi-Civita connection

As an example, suppose that M carries a Riemannian metric, and consider the Levi-Civita connection on the tangent bundle of M.[1] A local frame on the tangent bundle is an ordered list of vector fields e = (ei | i = 1,2,...,n=dim M) defined on an open subset of M that are linearly independent at every point of their domain. The Christoffel symbols define the Levi-Civita connection by

If θ = (θi | i=1,2,...,n), denotes the dual basis of the cotangent bundle, such that θi(ej) = δij (the Kronecker delta), then the connection form is

In terms of the connection form, the exterior connection on a vector field v = Σieivi is given by

One can recover the Levi-Civita connection, in the usual sense, from this by contracting with ei:

Curvature

The curvature 2-form of the Levi-Civita connection is the matrix (Ωij) given by

For simplicity, suppose that the frame e is holonomic, so that dθi=0.[2] Then, employing now the summation convention on repeated indices,

where R is the Riemann curvature tensor.

Torsion

The Levi-Civita connection is characterized as the unique metric connection in the tangent bundle with zero torsion. To describe the torsion, note that the vector bundle E is the tangent bundle. This carries a canonical solder form (sometimes called the canonical one-form) that is the section θ of Hom(TM,TM) = T*M ⊗ TM corresponding to the identity endomorphism of the tangent spaces. In the frame e, the solder form is θ = Σi ei ⊗ θi, where again θi is the dual basis.

The torsion of the connection is given by Θ = D θ, or in terms of the frame components of the solder form by

Assuming again for simplicity that e is holonomic, this expression reduces to

,

which vanishes if and only if Γikj is symmetric on its lower indices.

Structure groups

A more specific type of connection form can be constructed when the vector bundle E carries a structure group. This amounts to a preferred class of frames e on E, which are related by a Lie group G. For example, in the presence of a metric in E, one works with frames that form an orthonormal basis at each point. The structure group is then the orthogonal group, since this group preserves the orthonormality of frames. Other examples include:

In general, let E be a given vector bundle of fibre dimension k and G ⊂ GL(k) a given Lie subgroup of the general linear group of Rk. If (eα) is a local frame of E, then a matrix-valued function (gij): MG may act on the eα to produce a new frame

Two such frames are G-related. Informally, the vector bundle E has the structure of a G-bundle if a preferred class of frames is specified, all of which are locally G-related to each other. In formal terms, E is a fibre bundle with structure group G whose typical fibre is Rk with the natural action of G as a subgroup of GL(k).

Compatible connections

A connection is compatible with the structure of a G-bundle on E provided that the associated parallel transport maps always send one G-frame to another. Formally, along a curve γ, the following must hold locally (that is, for sufficiently small values of t):

for some matrix gαβ (which may also depend on t). Differentiation at t=0 gives

where the coefficients ωαβ are in the Lie algebra g of the Lie group G.

With this observation, the connection form ωαβ defined by

is compatible with the structure if the matrix of one-forms ωαβ(e) takes its values in g.

The curvature form of a compatible connection is, moreover, a g-valued two-form.

Change of frame

Under a change of frame

where g is a G-valued function defined on an open subset of M, the connection form transforms via

Or, using matrix products:

To interpret each of these terms, recall that g : MG is a G-valued (locally defined) function. With this in mind,

where ωg is the Maurer-Cartan form for the group G, here pulled back to M along the function g, and Ad is the adjoint representation of G on its Lie algebra.

Principal bundles

The connection form, as introduced thus far, depends on a particular choice of frame. In the first definition, the frame is just a local basis of sections. To each frame, a connection form is given with a transformation law for passing from one frame to another. In the second definition, the frames themselves carry some additional structure provided by a Lie group, and changes of frame are constrained to those that take their values in it. The language of principal bundles, pioneered by Charles Ehresmann in the 1940s, provides a manner of organizing these many connection forms and the transformation laws connecting them into a single intrinsic form with a single rule for transformation. The disadvantage to this approach is that the forms are no longer defined on the manifold itself, but rather on a larger principal bundle.

The principal connection for a connection form

Suppose that EM is a vector bundle with structure group G. Let {U} be an open cover of M, along with G-frames on each U, denoted by eU. These are related on the intersections of overlapping open sets by

for some G-valued function hUV defined on UV.

Let FGE be the set of all G-frames taken over each point of M. This is a principal G-bundle over M. In detail, using the fact that the G-frames are all G-related, FGE can be realized in terms of gluing data among the sets of the open cover:

where the equivalence relation is defined by

On FGE, define a principal G-connection as follows, by specifying a g-valued one-form on each product U × G, which respects the equivalence relation on the overlap regions. First let

be the projection maps. Now, for a point (x,g) ∈ U × G, set

The 1-form ω constructed in this way respects the transitions between overlapping sets, and therefore descends to give a globally defined 1-form on the principal bundle FGE. It can be shown that ω is a principal connection in the sense that it reproduces the generators of the right G action on FGE, and equivariantly intertwines the right action on T(FGE) with the adjoint representation of G.

Connection forms associated to a principal connection

Conversely, a principal G-connection ω in a principal G-bundle PM gives rise to a collection of connection forms on M. Suppose that e : MP is a local section of P. Then the pullback of ω along e defines a g-valued one-form on M:

Changing frames by a G-valued function g, one sees that ω(e) transforms in the required manner by using the Leibniz rule, and the adjunction:

where X is a vector on M, and d denotes the pushforward.

See also

Notes

  1. See Template:Harvtxt, II.7 for a complete account of the Levi-Civita connection from this point of view.
  2. In a non-holonomic frame, the expression of curvature is further complicated by the fact that the derivatives dθi must be taken into account.
  3. Wells (1973).
  4. See for instance Kobayashi and Nomizu, Volume II.
  5. Wells, ibid.
  6. See Chern and Moser.

References

  • Chern, S.-S., Topics in Differential Geometry, Institute for Advanced Study, mimeographed lecture notes, 1951.
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    Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.

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    Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.

    In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.

    Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region

    Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.

    15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.

    To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010
  • Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.

    Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.

    In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.

    Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region

    Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.

    15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.

    To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010
  • Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.

    Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.

    In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.

    Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region

    Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.

    15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.

    To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010
  • Many property agents need to declare for the PIC grant in Singapore. However, not all of them know find out how to do the correct process for getting this PIC scheme from the IRAS. There are a number of steps that you need to do before your software can be approved.

    Naturally, you will have to pay a safety deposit and that is usually one month rent for annually of the settlement. That is the place your good religion deposit will likely be taken into account and will kind part or all of your security deposit. Anticipate to have a proportionate amount deducted out of your deposit if something is discovered to be damaged if you move out. It's best to you'll want to test the inventory drawn up by the owner, which can detail all objects in the property and their condition. If you happen to fail to notice any harm not already mentioned within the inventory before transferring in, you danger having to pay for it yourself.

    In case you are in search of an actual estate or Singapore property agent on-line, you simply should belief your intuition. It's because you do not know which agent is nice and which agent will not be. Carry out research on several brokers by looking out the internet. As soon as if you end up positive that a selected agent is dependable and reliable, you can choose to utilize his partnerise in finding you a home in Singapore. Most of the time, a property agent is taken into account to be good if he or she locations the contact data on his website. This may mean that the agent does not mind you calling them and asking them any questions relating to new properties in singapore in Singapore. After chatting with them you too can see them in their office after taking an appointment.

    Have handed an trade examination i.e Widespread Examination for House Brokers (CEHA) or Actual Property Agency (REA) examination, or equal; Exclusive brokers are extra keen to share listing information thus making certain the widest doable coverage inside the real estate community via Multiple Listings and Networking. Accepting a severe provide is simpler since your agent is totally conscious of all advertising activity related with your property. This reduces your having to check with a number of agents for some other offers. Price control is easily achieved. Paint work in good restore-discuss with your Property Marketing consultant if main works are still to be done. Softening in residential property prices proceed, led by 2.8 per cent decline within the index for Remainder of Central Region

    Once you place down the one per cent choice price to carry down a non-public property, it's important to accept its situation as it is whenever you move in – faulty air-con, choked rest room and all. Get round this by asking your agent to incorporate a ultimate inspection clause within the possibility-to-buy letter. HDB flat patrons routinely take pleasure in this security net. "There's a ultimate inspection of the property two days before the completion of all HDB transactions. If the air-con is defective, you can request the seller to repair it," says Kelvin.

    15.6.1 As the agent is an intermediary, generally, as soon as the principal and third party are introduced right into a contractual relationship, the agent drops out of the image, subject to any problems with remuneration or indemnification that he could have against the principal, and extra exceptionally, against the third occasion. Generally, agents are entitled to be indemnified for all liabilities reasonably incurred within the execution of the brokers´ authority.

    To achieve the very best outcomes, you must be always updated on market situations, including past transaction information and reliable projections. You could review and examine comparable homes that are currently available in the market, especially these which have been sold or not bought up to now six months. You'll be able to see a pattern of such report by clicking here It's essential to defend yourself in opposition to unscrupulous patrons. They are often very skilled in using highly unethical and manipulative techniques to try and lure you into a lure. That you must also protect your self, your loved ones, and personal belongings as you'll be serving many strangers in your home. Sign a listing itemizing of all of the objects provided by the proprietor, together with their situation. HSR Prime Recruiter 2010

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