YIMBY

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/YIMBY 

YIMBY is an acronym for "yes, in my back yard", a pro-housing movement in contrast and opposition to the NIMBY ("not in my back yard") phenomenon. The YIMBY position supports increasing the supply of housing within cities where housing costs have escalated to unaffordable levels. YIMBYs often seek rezoning that would allow denser housing to be produced or the repurposing of obsolete buildings, such as shopping malls, into housing. Some YIMBYs have also supported public-interest projects like clean energy or alternative transport.

The YIMBY movement has supporters across the political spectrum including left-leaning adherents who believe housing production is a social justice issue and free-market libertarian proponents who think the supply of housing should not be regulated by the government. YIMBYs argue cities can be made increasingly affordable and accessible by building more infill housing, and that greenhouse gas emissions will be reduced by denser cities.

History

A 1993 essay published in the Journal of the American Planning Association entitled "Planners' Alchemy, Transforming NIMBY to YIMBY: Rethinking NIMBY" used 'YIMBY' in general reference to development, not only housing development.

The pro-housing YIMBY position emerged in regions experiencing unaffordable housing prices. The Guardian and Raidió Teilifís Éireann say this movement began in the San Francisco Bay area in the 2010s due to high housing costs created as a result of the local technology industry adding many more jobs to the region than the number of housing units constructed in the same time span.

Political debate

The debate over YIMBY policies does not follow the usual political lines. The YIMBY coalition includes libertarians, leftists, the tech industry, affordable-housing developers, labor groups, and environmental groups.

Because "NIMBY" is a pejorative, self-identified NIMBYs are rare, but opposition to YIMBY policies comes from other leftists, right-wing figures like Donald Trump and Tucker Carlson, historical preservationists, local power brokers, wealthy homeowners concerned about their property values, and renter advocates concerned about displacement and gentrification who disagree with the prevailing view among progressive housing economists that displacement is caused by lack of enough housing.

In terms of public opinion, support for more infill development is higher among renters, Democrats, and black people, though it enjoys majority support among all groups in California. In general, support for development is higher when the development is less local. For example, a statewide upzoning bill will have more popular support statewide than a new apartment building will have from the immediate neighbors. For example, while the national Sierra Club is in favor of infill development, local Sierra Club chapters oppose making development easier in their own cities. Because of this, YIMBYs have attempted to reduce local discretion over housing construction in order to move decision-making to a level which is more pro-development.

The particular contours of housing politics have led to some unusual political bedfellows and accompanying political beliefs. For example, opposition to market-rate housing has been branded as "PHIMBY", for "public housing in my backyard"; because new public housing in the United States is currently illegal to construct, this is, in effect, the same as NIMBYism. Similarly, refusal to support any non-subsidized housing or requiring an unrealistically high inclusionary (i.e., subsidized) percentage for new construction has the same result, as subsidized homes are more expensive to build than market-rate ones. The origins of the modern YIMBY movement are separate from pre-existing tenants' rights groups, which are suspicious of their association with young, white technology workers and may be wary of disrupting the status quo, which allows incumbent groups to use discretionary planning processes to negotiate for benefits while slowing development in general. This can manifest as "vacancy trutherism", the idea that most new apartments or condos remain empty even in high-demand cities and therefore will not alleviate the housing crisis. (This is untrue; vacancies are negatively correlated with rising rents.) It can also manifest in a belief that new housing in an expensive city draws more migration than it houses, and will actually worsen the housing crisis via induced demand. (This is also untrue; adding more housing reduces rents.)

Academic research

Academic research has yielded some generalizable results on the effects of upzoning, the root causes of unaffordability, and the most efficacious policy prescriptions to help low-income workers in prosperous cities.

Housing supply and prices

Studies show that strict land use regulations reduce housing supply and raise the price of houses and land.

Research into the granular effects of additional housing supply show that new housing units in hot markets do not increase nearby rents: the effect on demand pressure is greater than the amenity effect. This has been observed in New York City, in San Francisco, in Helsinki, and across multiple cities. Additionally, in California, new market-rate housing reduced displacement and slowed rises in rent.

Upzoning (rezoning for more housing) in the absence of additional housing production appeared to raise prices in Chicago, though the author disputed that this could lead to general conclusions about the affordability effects of upzoning.

Another study published in Urban Studies in 2006 observed price trends within Canadian cities and noted very slow price drops for older housing over a period of decades; the author concluded that newly constructed housing would not become affordable in the near future, meaning that filtering was not a viable method for producing affordable housing, especially in the most expensive cities.

Affordability and homelessness

The change in rent is inversely proportional to vacancy rates in a city, which are related to the demand for housing and the rate of construction. Homelessness rates are correlated with higher rents, with an inflection point where the median rent passes thirty percent of the median income.

Racial segregation

Research shows that strict land use regulations contribute to racial housing segregation in the United States. Surveys have shown that white communities are more likely to have strict land use regulations and whites are more likely to support those regulations.

Economy

A 2019 study by Chang-Tai Hsieh and Enrico Moretti in the American Economic Journal found that liberalization of land use regulations would lead to enormous productivity gains. The study estimated that strict land use regulations "lowered aggregate US growth by 36 percent from 1964 to 2009."

Examples

Canada

In Toronto, a self-styled YIMBY movement was established in 2006 by community members in response to significant development proposals in the West Queen West area, and a YIMBY festival, launched the same year, has been held annually since. The festival's organizer stated that "YIMBYism is a community mindset that's open to change and development." An advocacy group called HousingNowTO fights to maximize the number of homes when the government builds housing. Another group, More Neighbours Toronto (MNTO), advocates for policy changes to increase the housing supply.

In Vancouver, Abundant Housing Vancouver was formed in 2016 to support more housing.

Slovakia

In 2014, the blog YIMBY Bratislava was created as a response to rising aversion to development in Bratislava, the capital of Slovakia. The blog informs about development in the city, promotes it, but also criticizes it. In 2018 it was renamed to YIM.BA — Yes In My Bratislava. It's a private blog of one author with the fan group of its readers and fans on Facebook.

Sweden

Yimby is an independent political party network founded in Stockholm in 2007, which advocates physical development, densification and promotion of urban environment with chapters in Stockholm, Gothenburg, and Uppsala. The group believes that the PBL (Plans and Constructions Act, from 1987) is a major impediment to any new construction, and should be eliminated or dramatically reformed.

United Kingdom

London YIMBY was set up in 2016, publishing its first report with the Adam Smith Institute in 2017 which received national press coverage. Its members advocate a policy termed 'Better Streets'. This proposal would allow residents of individual streets to vote by a two-thirds majority to pick a design code and allow extensions or replacement buildings of up to five or six stories, allowing suburban homes to be gradually replaced by mansion blocks. This flagship policy has achieved a degree of recognition, being endorsed by former Liberal Democrat MP Sam Gyimah and the leader of the House of Commons Jacob Rees-Mogg.

Other YIMBY groups have been set up in individual London boroughs and in cities suffering similar housing shortages, such as Brighton, Bristol and Edinburgh.

Members of the British YIMBY movement have been critical of established planning organisations such as the Town and Country Planning Association and the Campaign to Protect Rural England, accusing them of pursuing policies that worsen Britain's housing shortage.

United States

California

The YIMBY movement has been particularly strong in California, a state experiencing a substantial housing shortage crisis. Since 2017, YIMBY groups in California have pressured California state and its localities to pass laws to expedite housing construction, follow their own zoning laws, and reduce the stringency of zoning regulations. YIMBY activists have also been active in helping to enforce state law on housing by bringing law-breaking cities to the attention of authorities.

Since 2014, in response to California's housing affordability crisis, several YIMBY groups were created in the San Francisco Bay Area. These groups have lobbied both locally and at the state level for increased housing production at all price levels, as well as using California's Housing Accountability Act (the "anti-NIMBY law") to sue cities when they attempt to block or downsize housing development. The New York Times explained about one organization: "Members want San Francisco and its suburbs to build more of every kind of housing. More subsidized affordable housing, more market-rate rentals, more high-end condominiums."

In 2017, YIMBY groups successfully lobbied for the passage of Senate Bill 35 (SB 35), which streamlines housing under certain criteria, among other "housing package" of bills.

From 2018 to 2020, the lobbying group California YIMBY joined over 100 Bay Area technology industry executives in supporting state senator Scott Wiener's Senate Bills 827 and 50. The bills failed in the state senate after multiple attempts at passage. California YIMBY received $100,000 from Yelp CEO Jeremy Stoppelman, $1 million from Irish entrepreneurs John and Patrick Collison through their company, Stripe, and $500,000 raised by Pantheon CEO Zach Rosen and GitHub CEO Nat Friedman.

YIMBY groups in California have supported the split roll effort to eliminate Proposition 13 protections for commercial properties, and supported the ballot measure known as Proposition 15, which would implement this change but failed to pass in 2020. This change would have potentially incentivized local governments to approve commercial property development (for its attendant business, payroll, sales and property tax revenue) over residential development and would not have provided funding earmarked for affordable housing development.

Massachusetts

Since 2012, several YIMBY groups were established in the greater Boston area. One group argues that "...more smart housing development is the only way to retain a middle class in pricey cities like Boston and Cambridge."

New York

Several YIMBY groups, chiefly Open New York, have been created in New York City; according to an organizer: "In high-opportunity areas where people actually really want to live, the well-heeled, mostly white residents are able to use their perceived political power to stop the construction of basically anything," adding that low-income communities don't share that ability to keep development at bay: "Philosophically, we think that the disproportionate share of the burden of growth has been borne by low income, minority or industrial neighborhoods for far too long.".

In 2011, a news website called `New York YIMBY` was created that focuses on construction trends in New York City. While this news website is not strictly related to YIMBY political movement, in an interview with Politico, the creator of the site stated: "Zoning is the problem, not development in this city. I think people don't really understand that."

International

In September 2018, the third annual Yes In My Backyard conference, named "YIMBYTown" occurred in Boston, hosted by that area's YIMBY community. The first YIMBY conference was held in 2016 in Boulder, Colorado and hosted by a group that included Boulder's former mayor, who commented that: "It is clearer than ever that if we really care about solving big national issues like inequality and climate change, tackling the lack of housing in thriving urban areas, caused largely by local zoning restrictions, is key." The second annual conference was held in the San Francisco Bay Area city of Oakland, California. These conferences have attracted attendees from the United States, as well as some from Canada, England, Australia, and other countries.

Galilean transformation

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Galilean_transformation 

In physics, a Galilean transformation is used to transform between the coordinates of two reference frames which differ only by constant relative motion within the constructs of Newtonian physics. These transformations together with spatial rotations and translations in space and time form the inhomogeneous Galilean group (assumed throughout below). Without the translations in space and time the group is the homogeneous Galilean group. The Galilean group is the group of motions of Galilean relativity acting on the four dimensions of space and time, forming the Galilean geometry. This is the passive transformation point of view. In special relativity the homogenous and inhomogenous Galilean transformations are, respectively, replaced by the Lorentz transformations and Poincaré transformations; conversely, the group contraction in the classical limit c → ∞ of Poincaré transformations yields Galilean transformations.

The equations below are only physically valid in a Newtonian framework, and not applicable to coordinate systems moving relative to each other at speeds approaching the speed of light.

Galileo formulated these concepts in his description of uniform motion. The topic was motivated by his description of the motion of a ball rolling down a ramp, by which he measured the numerical value for the acceleration of gravity near the surface of the Earth.

Translation

Standard configuration of coordinate systems for Galilean transformations.

Although the transformations are named for Galileo, it is the absolute time and space as conceived by Isaac Newton that provides their domain of definition. In essence, the Galilean transformations embody the intuitive notion of addition and subtraction of velocities as vectors.

The notation below describes the relationship under the Galilean transformation between the coordinates (x, y, z, t) and (x′, y′, z′, t′) of a single arbitrary event, as measured in two coordinate systems S and S′, in uniform relative motion (velocity v) in their common x and x′ directions, with their spatial origins coinciding at time t = t′ = 0:

${\displaystyle x'=x-vt}$

${\displaystyle y'=y}$

${\displaystyle z'=z}$

${\displaystyle t'=t.}$

Note that the last equation holds for all Galilean transformations up to addition of a constant, and expresses the assumption of a universal time independent of the relative motion of different observers.

In the language of linear algebra, this transformation is considered a shear mapping, and is described with a matrix acting on a vector. With motion parallel to the x-axis, the transformation acts on only two components:

${\displaystyle {\begin{pmatrix}x'\\t'\end{pmatrix}}={\begin{pmatrix}1&-v\\0&1\end{pmatrix}}{\begin{pmatrix}x\\t\end{pmatrix}}}$

Though matrix representations are not strictly necessary for Galilean transformation, they provide the means for direct comparison to transformation methods in special relativity.

Galilean transformations

The Galilean symmetries can be uniquely written as the composition of a rotation, a translation and a uniform motion of spacetime. Let x represent a point in three-dimensional space, and t a point in one-dimensional time. A general point in spacetime is given by an ordered pair (x, t).

A uniform motion, with velocity v, is given by

${\displaystyle (\mathbf {x} ,t)\mapsto (\mathbf {x} +t\mathbf {v} ,t),}$

where v ∈ R³. A translation is given by

${\displaystyle (\mathbf {x} ,t)\mapsto (\mathbf {x} +\mathbf {a} ,t+s),}$

where a ∈ R³ and s ∈ R. A rotation is given by

${\displaystyle (\mathbf {x} ,t)\mapsto (R\mathbf {x} ,t),}$

where R : R³ → R³ is an orthogonal transformation.

As a Lie group, the group of Galilean transformations has dimension 10.

Galilean group

Two Galilean transformations G(R, v, a, s) and G(R' , v′, a′, s′) compose to form a third Galilean transformation,

G(R′, v′, a′, s′) ⋅ G(R, v, a, s) = G(R′ R, R′ v + v′, R′ a + a′ + v′ s, s′ + s).

The set of all Galilean transformations Gal(3) forms a group with composition as the group operation.

The group is sometimes represented as a matrix group with spacetime events (x, t, 1) as vectors where t is real and x ∈ R³ is a position in space. The action is given by

${\displaystyle {\begin{pmatrix}R&v&a\\0&1&s\\0&0&1\end{pmatrix}}{\begin{pmatrix}x\\t\\1\end{pmatrix}}={\begin{pmatrix}Rx+vt+a\\t+s\\1\end{pmatrix}},}$

where s is real and v, x, a ∈ R³ and R is a rotation matrix. The composition of transformations is then accomplished through matrix multiplication. Care must be taken in the discussion whether one restricts oneself to the connected component group of the orthogonal transformations.

Gal(3) has named subgroups. The identity component is denoted SGal(3).

Let m represent the transformation matrix with parameters v, R, s, a:

• ${\displaystyle \{m:R=I_{3}\},}$ anisotropic transformations.
• ${\displaystyle \{m:s=0\},}$ isochronous transformations.
• ${\displaystyle \{m:s=0,v=0\},}$ spatial Euclidean transformations.
• ${\displaystyle G_{1}=\{m:s=0,a=0\},}$ uniformly special transformations / homogenous transformations, isomorphic to Euclidean transformations.
• ${\displaystyle G_{2}=\{m:v=0,R=I_{3}\}\cong \left(\mathbf {R} ^{4},+\right),}$ shifts of origin / translation in Newtonian spacetime.
• ${\displaystyle G_{3}=\{m:s=0,a=0,v=0\}\cong \mathrm {SO} (3),}$ rotations (of reference frame) (see SO(3)), a compact group.
• ${\displaystyle G_{4}=\{m:s=0,a=0,R=I_{3}\}\cong \left(\mathbf {R} ^{3},+\right),}$ uniform frame motions / boosts.

The parameters s, v, R, a span ten dimensions. Since the transformations depend continuously on s, v, R, a, Gal(3) is a continuous group, also called a topological group.

The structure of Gal(3) can be understood by reconstruction from subgroups. The semidirect product combination (${\displaystyle A\rtimes B}$) of groups is required.

1. ${\displaystyle G_{2}\triangleleft \mathrm {SGal} (3)}$ (G₂ is a normal subgroup)
2. ${\displaystyle \mathrm {SGal} (3)\cong G_{2}\rtimes G_{1}}$
3. ${\displaystyle G_{4}\trianglelefteq G_{1}}$
4. ${\displaystyle G_{1}\cong G_{4}\rtimes G_{3}}$
5. ${\displaystyle \mathrm {SGal} (3)\cong \mathbf {R} ^{4}\rtimes (\mathbf {R} ^{3}\rtimes \mathrm {SO} (3)).}$

Origin in group contraction

The Lie algebra of the Galilean group is spanned by H, P_i, C_i and L_ij (an antisymmetric tensor), subject to commutation relations, where

${\displaystyle [H,P_{i}]=0}$

${\displaystyle [P_{i},P_{j}]=0}$

${\displaystyle [L_{ij},H]=0}$

${\displaystyle [C_{i},C_{j}]=0}$

${\displaystyle [L_{ij},L_{kl}]=i[\delta _{ik}L_{jl}-\delta _{il}L_{jk}-\delta _{jk}L_{il}+\delta _{jl}L_{ik}]}$

${\displaystyle [L_{ij},P_{k}]=i[\delta _{ik}P_{j}-\delta _{jk}P_{i}]}$

${\displaystyle [L_{ij},C_{k}]=i[\delta _{ik}C_{j}-\delta _{jk}C_{i}]}$

${\displaystyle [C_{i},H]=iP_{i}\,\!}$

${\displaystyle [C_{i},P_{j}]=0~.}$

H is the generator of time translations (Hamiltonian), P_i is the generator of translations (momentum operator), C_i is the generator of rotationless Galilean transformations (Galileian boosts), and L_ij stands for a generator of rotations (angular momentum operator).

This Lie Algebra is seen to be a special classical limit of the algebra of the Poincaré group, in the limit c → ∞. Technically, the Galilean group is a celebrated group contraction of the Poincaré group (which, in turn, is a group contraction of the de Sitter group SO(1,4)). Formally, renaming the generators of momentum and boost of the latter as in

P₀ ↦ H / c

K_i ↦ c ⋅ C_i,

where c is the speed of light (or any unbounded function thereof), the commutation relations (structure constants) in the limit c → ∞ take on the relations of the former. Generators of time translations and rotations are identified. Also note the group invariants L_mn L^mn and P_i Pⁱ.

In matrix form, for d = 3, one may consider the regular representation (embedded in GL(5; R), from which it could be derived by a single group contraction, bypassing the Poincaré group),

${\displaystyle iH=\left({\begin{array}{ccccc}0&0&0&0&0\\0&0&0&0&0\\0&0&0&0&0\\0&0&0&0&1\\0&0&0&0&0\\\end{array}}\right),\qquad }$ ${\displaystyle i{\vec {a}}\cdot {\vec {P}}=\left({\begin{array}{ccccc}0&0&0&0&a_{1}\\0&0&0&0&a_{2}\\0&0&0&0&a_{3}\\0&0&0&0&0\\0&0&0&0&0\\\end{array}}\right),\qquad }$ ${\displaystyle i{\vec {v}}\cdot {\vec {C}}=\left({\begin{array}{ccccc}0&0&0&v_{1}&0\\0&0&0&v_{2}&0\\0&0&0&v_{3}&0\\0&0&0&0&0\\0&0&0&0&0\\\end{array}}\right),\qquad }$ ${\displaystyle i\theta _{i}\epsilon ^{ijk}L_{jk}=\left({\begin{array}{ccccc}0&\theta _{3}&-\theta _{2}&0&0\\-\theta _{3}&0&\theta _{1}&0&0\\\theta _{2}&-\theta _{1}&0&0&0\\0&0&0&0&0\\0&0&0&0&0\\\end{array}}\right)~.}$

The infinitesimal group element is then

${\displaystyle G(R,{\vec {v}},{\vec {a}},s)=1\!\!1_{5}+\left({\begin{array}{ccccc}0&\theta _{3}&-\theta _{2}&v_{1}&a_{1}\\-\theta _{3}&0&\theta _{1}&v_{2}&a_{2}\\\theta _{2}&-\theta _{1}&0&v_{3}&a_{3}\\0&0&0&0&s\\0&0&0&0&0\\\end{array}}\right)+\ ...~.}$

Central extension of the Galilean group

One may consider a central extension of the Lie algebra of the Galilean group, spanned by H′, P′_i, C′_i, L′_ij and an operator M: The so-called Bargmann algebra is obtained by imposing ${\displaystyle [C'_{i},P'_{j}]=iM\delta _{ij}}$, such that M lies in the center, i.e. commutes with all other operators.

In full, this algebra is given as

${\displaystyle [H',P'_{i}]=0\,\!}$

${\displaystyle [P'_{i},P'_{j}]=0\,\!}$

${\displaystyle [L'_{ij},H']=0\,\!}$

${\displaystyle [C'_{i},C'_{j}]=0\,\!}$

${\displaystyle [L'_{ij},L'_{kl}]=i[\delta _{ik}L'_{jl}-\delta _{il}L'_{jk}-\delta _{jk}L'_{il}+\delta _{jl}L'_{ik}]\,\!}$

${\displaystyle [L'_{ij},P'_{k}]=i[\delta _{ik}P'_{j}-\delta _{jk}P'_{i}]\,\!}$

${\displaystyle [L'_{ij},C'_{k}]=i[\delta _{ik}C'_{j}-\delta _{jk}C'_{i}]\,\!}$

${\displaystyle [C'_{i},H']=iP'_{i}\,\!}$

and finally

${\displaystyle [C'_{i},P'_{j}]=iM\delta _{ij}~.}$

where the new parameter ${\displaystyle M}$ shows up. This extension and projective representations that this enables is determined by its group cohomology.