Linear programming relaxation

In abstract algebra, a heap (sometimes also called a groud) is a mathematical generalization of a group. Informally speaking, a heap is obtained from a group by "forgetting" which element is the unit, in the same way that an affine space can be viewed as a vector space in which the 0 element has been "forgotten". A heap is essentially the same thing as a torsor, and the category of heaps is equivalent to the category of torsors, with morphisms given by transport of structure under group homomorphisms, but the theory of heaps emphasizes the intrinsic composition law, rather than global structures such as the geometry of bundles.

Formally, a heap is an algebraic structure consisting of a non-empty set H with a ternary operation denoted $[x,y,z]\in H$ which satisfies

• the para-associative law

$[[a,b,c],d,e]=[a,[d,c,b],e]=[a,b,[c,d,e]]\ \forall \ a,b,c,d,e\in H$

• the identity law

$[a,a,x]=[x,a,a]=x\ \forall \ a,x\in H.$

A group can be regarded as a heap under the operation $[x,y,z]=xy^{-1}z$. Conversely, let H be a heap, and choose an element e ∈H. The binary operation $x*y=[x,e,y]$ makes H into a group with identity e and inverse $x^{-1}=[e,x,e]$. A heap can thus be regarded as a group in which the identity has yet to be decided.

Whereas the automorphisms of a single object form a group, the set of isomorphisms between two isomorphic objects naturally forms a heap, with the operation $[f,g,h]=fg^{-1}h$ (here juxtaposition denotes composition of functions). This heap becomes a group once a particular isomorphism by which the two objects are to be identified is chosen.

Examples

Two element heap

If $H=\{a,b\}$ then the following structure is a heap:

$[a,a,a]=a,\,[a,a,b]=b,\,[b,a,a]=b,\,[b,a,b]=a,$

$[a,b,a]=b,\,[a,b,b]=a,\,[b,b,a]=a,\,[b,b,b]=b.$

Heap of a group

As noted above, any group becomes a heap under the operation

$[x,y,z]=xy^{-1}z.$

One important special case:

Heap of integers

If $x,y,z$ are integers, we can set $[x,y,z]=x-y+z$ to produce a heap. We can then choose any integer $k$ to be the identity of a new group on the set of integers, with the operation $*$

$x*y=x+y-k$

and inverse

$x^{-1}=2k-x$.

Generalizations and related concepts

• A pseudoheap or pseudogroud satisfies the partial para-associative condition

$[[a,b,c],d,e]=[a,b,[c,d,e]].$

• A semiheap or semigroud is required to satisfy only the para-associative law but need not obey the identity law.

An example of a semigroud that is not in general a groud is given by M a ring of matrices of fixed size with

$[x,y,z]=x\cdot y^{\top }\cdot z$

where • denotes matrix multiplication and ⊤ denotes matrix transpose.

• An idempotent semiheap is a semiheap where $[a,a,a]=a$ for all a.
• A generalised heap or generalised groud is an idempotent semiheap where

$[a,a,[b,b,x]]=[b,b,[a,a,x]]$ and $[[x,a,a],b,b]=[[x,b,b],a,a]$ for all a and b.

A semigroud is a generalised groud if the relation → defined by

$a\rightarrow b\Leftrightarrow [a,b,a]=a$

is reflexive (idempotence) and anti-symmetric. In a generalised groud, → is an order relation.

• A torsor is an equivalent notion to a heap which places more emphasis on the associated group. Any $G$-torsor $X$ is a heap under the operation $[x,y,z]=(x/y)\cdot z$. Conversely, if $X$ is a heap, any $x,y\in X$ define a permutation $\varphi _{x,y}(z)=[x,y,z]$ of $X$. If we let $G$ be the set of all such permutations $\varphi _{x,y}$, then $G$ is a group and $X$ is a $G$-torsor under the natural action.

Notes

43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.

References

• 20 year-old Real Estate Agent Rusty from Saint-Paul, has hobbies and interests which includes monopoly, property developers in singapore and poker. Will soon undertake a contiki trip that may include going to the Lower Valley of the Omo.
  
  My blog: http://www.primaboinca.com/view_profile.php?userid=5889534
• One of the biggest reasons investing in a Singapore new launch is an effective things is as a result of it is doable to be lent massive quantities of money at very low interest rates that you should utilize to purchase it. Then, if property values continue to go up, then you'll get a really high return on funding (ROI). Simply make sure you purchase one of the higher properties, reminiscent of the ones at Fernvale the Riverbank or any Singapore landed property Get Earnings by means of Renting
  
  In its statement, the singapore property listing - website link, government claimed that the majority citizens buying their first residence won't be hurt by the new measures. Some concessions can even be prolonged to chose teams of consumers, similar to married couples with a minimum of one Singaporean partner who are purchasing their second property so long as they intend to promote their first residential property. Lower the LTV limit on housing loans granted by monetary establishments regulated by MAS from 70% to 60% for property purchasers who are individuals with a number of outstanding housing loans on the time of the brand new housing purchase. Singapore Property Measures - 30 August 2010 The most popular seek for the number of bedrooms in Singapore is 4, followed by 2 and three. Lush Acres EC @ Sengkang
  
  Discover out more about real estate funding in the area, together with info on international funding incentives and property possession. Many Singaporeans have been investing in property across the causeway in recent years, attracted by comparatively low prices. However, those who need to exit their investments quickly are likely to face significant challenges when trying to sell their property – and could finally be stuck with a property they can't sell. Career improvement programmes, in-house valuation, auctions and administrative help, venture advertising and marketing, skilled talks and traisning are continuously planned for the sales associates to help them obtain better outcomes for his or her shoppers while at Knight Frank Singapore. No change Present Rules
  
  Extending the tax exemption would help. The exemption, which may be as a lot as $2 million per family, covers individuals who negotiate a principal reduction on their existing mortgage, sell their house short (i.e., for lower than the excellent loans), or take part in a foreclosure course of. An extension of theexemption would seem like a common-sense means to assist stabilize the housing market, but the political turmoil around the fiscal-cliff negotiations means widespread sense could not win out. Home Minority Chief Nancy Pelosi (D-Calif.) believes that the mortgage relief provision will be on the table during the grand-cut price talks, in response to communications director Nadeam Elshami. Buying or promoting of blue mild bulbs is unlawful.
  
  A vendor's stamp duty has been launched on industrial property for the primary time, at rates ranging from 5 per cent to 15 per cent. The Authorities might be trying to reassure the market that they aren't in opposition to foreigners and PRs investing in Singapore's property market. They imposed these measures because of extenuating components available in the market." The sale of new dual-key EC models will even be restricted to multi-generational households only. The models have two separate entrances, permitting grandparents, for example, to dwell separately. The vendor's stamp obligation takes effect right this moment and applies to industrial property and plots which might be offered inside three years of the date of buy. JLL named Best Performing Property Brand for second year running
  
  The data offered is for normal info purposes only and isn't supposed to be personalised investment or monetary advice. Motley Fool Singapore contributor Stanley Lim would not personal shares in any corporations talked about. Singapore private home costs increased by 1.eight% within the fourth quarter of 2012, up from 0.6% within the earlier quarter. Resale prices of government-built HDB residences which are usually bought by Singaporeans, elevated by 2.5%, quarter on quarter, the quickest acquire in five quarters. And industrial property, prices are actually double the levels of three years ago. No withholding tax in the event you sell your property. All your local information regarding vital HDB policies, condominium launches, land growth, commercial property and more
  
  There are various methods to go about discovering the precise property. Some local newspapers (together with the Straits Instances ) have categorised property sections and many local property brokers have websites. Now there are some specifics to consider when buying a 'new launch' rental. Intended use of the unit Every sale begins with 10 p.c low cost for finish of season sale; changes to 20 % discount storewide; follows by additional reduction of fiftyand ends with last discount of 70 % or extra. Typically there is even a warehouse sale or transferring out sale with huge mark-down of costs for stock clearance. Deborah Regulation from Expat Realtor shares her property market update, plus prime rental residences and houses at the moment available to lease Esparina EC @ Sengkang