The different only shows up for field, not with particles. For fields, there are two types of changes that we can make that can keep the Lagrangian unchanged as mentioned at Physics from Symmetry by Jakob Schwichtenberg (2015) chapter "4.5.2 Noether's Theorem for Field Theories - Spacetime":
- spacetime symmetry: act with the Poincaré group on the Four-vector spacetime inputs of the field itself, i.e. transforming into
- internal symmetry: act on the output of the field, i.e.:
From the spacetime theory alone, we can derive the Lagrangian for the free theories for each spin:Then the internal symmetries are what add the interaction part of the Lagrangian, which then completes the Standard Model Lagrangian.
Node.js does have Node.js
worker_threads however.async is all present in JavaScript for two reasons:- you make network requests all the time
- JavaScript is single threaded, so if you are waiting for a network request, the UI freezes, see remarks on the deprecation of synchronous HTTP request at: developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest/Synchronous_and_Asynchronous_Requests
However, it is also Hell: how to convert
async to sync in JavaScript.God, it's impossible! You just have to convert the entire fucking call stack all the way up to async functions. It could mean refactoring hundreds of functions.
To be fair, there is a logic to this, if you put yourself within the crappiness of the JavaScript threading model. And Python is not that much better with its Global Interpreter Lock.
The problem is that async was introduced relatively late, previously we just had to use infinitely deep callback trees, which was worse:compared to the new infinitely more readable:But now we are in an endless period of transition between both worlds.
myAsync().then(ret => myAsync2(ret).then(ret2 => myAsync3(re3)))ret = await myAsync()
ret2 = await myAsync2(ret)
ret3 = await myAsync3(ret3)It is also worth mentioning that callbacks are still inescapable if you really want to fan out into a non-linear dependency graph, usually with
Promise.all:await Promise.all([
myAsync(1).then(ret => myAsync2(ret)),
myAsync(2).then(ret => myAsync2(ret)),
])Bibliography:
- stackoverflow.com/questions/21819858/how-to-wrap-async-function-calls-into-a-sync-function-in-node-js-or-javascript
- stackoverflow.com/questions/9121902/call-an-asynchronous-javascript-function-synchronously
- stackoverflow.com/questions/47227550/using-await-inside-non-async-function
- stackoverflow.com/questions/43832490/is-it-possible-to-use-await-without-async-in-js
- stackoverflow.com/questions/6921895/synchronous-delay-in-code-execution
And then, after many many hours of this work, you might notice that the new code is way, way way slower than before, because making small functions
async has a large performance impact: madelinemiller.dev/blog/javascript-promise-overhead/. Real world case with a 4x slowdown: github.com/ourbigbook/ourbigbook/tree/async-slow.Anyways, since you Googled here, you might as well learn the standard pattern to convert callbacks functions into async functions using a promise: stackoverflow.com/questions/4708787/get-password-from-input-using-node-js/71868483#71868483
WellSync, if you are gonna useSync this wonky language thing inSync one place, you might as well useSync it everywhereSync and make it more decent. See also: how to convert
async to sync in JavaScript.Their CLI debugger is a bit crap compared to GDB, basic functionality is either lacking or too verbose:Documentation at: nodejs.org/dist/latest-v16.x/docs/api/debugger.html
- stackoverflow.com/questions/65493221/how-to-break-at-a-specific-function-or-line-with-the-node-js-node-inspect-comman
- stackoverflow.com/questions/70486188/how-to-break-on-uncaught-exception-on-the-node-js-node-inspect-command-line-debu Some operations are only possible on the browser debug UI...
Quantum field theory lecture by Tobias Osborne (2017) Lecture 1 by 
Ciro Santilli 40 Updated 2025-07-16
Ciro Santilli 40 Updated 2025-07-16Bibliography review:
- Quantum Field Theory lecture notes by David Tong (2007) is the course basis
- quantum field theory in a nutshell by Anthony Zee (2010) is a good quick and dirty book to start
Course outline given:
- classical field theory
- quantum scalar field. Covers bosons, and is simpler to get intuition about.
- quantum Dirac field. Covers fermions
- interacting fields
- perturbation theory
- renormalization
Non-relativistic QFT is a limit of relativistic QFT, and can be used to describe for example condensed matter physics systems at very low temperature. But it is still very hard to make accurate measurements even in those experiments.
Mentions that "QFT is hard" because (a finite list follows???):But I guess that if you fully understand what that means precisely, QTF won't be too hard for you!
There are no nontrivial finite-dimensional unitary representations of the Poincaré group.
Notably, this is stark contrast with rotation symmetry groups (SO(3)) which appears in space rotations present in non-relativistic quantum mechanics.
www.youtube.com/watch?v=T58H6ofIOpE&t=5097 describes the relativistic particle in a box thought experiment with shrinking walls
Some usage examples under: Section "Sequelize example".
As of 2021, this library is extremely painful to use. It does feel semi-mature, but there are just too much horrible things going on;
- the documentation is a bit messy and misses a lot of stuff. The examples are often too short, and it is hard to understand what specific options they are talking about do because they lack clear input/expected output pairs. Examples:
- the implementation has several inelegant/unintuitive annoyances/requirements of code repetition that drive you mad.The association API feels notably bad, it took a few days for Ciro Santilli to learn to do what he considers "basic" association operations, knowledge which he dumped to: stackoverflow.com/questions/22958683/how-to-implement-many-to-many-association-in-sequelize/67973948#67973948See also: how to decide if an ORM is good?.
- bugs are piling up. It appears that many key devs left, and current maintainers are just not being able to keep up.
Some glaring issues are listed at the horrors of Sequelize.
- foreign keys are capitalized:
- you must give
foreignKeywhen using aliases, otherwise it fails subtely. That would be derived automatically. - stackoverflow.com/questions/41502699/return-flat-object-from-sequelize-with-association can't auto-flatten to reuse the database's
ORDER limitandoffsetdon't work withoutsubQuery: falsewhen doing includes! It is just too buggy. Examples of this can be found e.g. under nodejs/sequelize/many_to_many_same_model.js.- stackoverflow.com/questions/34059081/how-do-i-reference-an-association-when-creating-a-row-in-sequelize-without-assum hard to not duplicate foreign keys values everywhere
- stack traces permanently broken or requiring non-obvious configs:
- does not automatically update fields on hooks: github.com/sequelize/sequelize/issues/8586#issuecomment-422877555
- cannot change columns when other columns have constraints due to the backup table?
- you have to use
.get()forattributealiased fields, why? stackoverflow.com/questions/32649218/how-do-i-select-a-column-using-an-alias/69890944#69890944 .idgets added toSELECTno matter what, breakingGROUP BYunless you do horrible workarounds:- no simple built-in mechanism for transaction retries: Sequelize transaction retries
- impossible to do subqueries in general. Docs just tell you to use literals. This in particular prevents single query deletes with join as done at nodejs/sequelize/raw/many_to_many.js:Also, you can't get query strings either: github.com/sequelize/sequelize/issues/2325
- sequelize.org/master/manual/sub-queries.html: the docs actually just tell you to use literals, lol
- stackoverflow.com/questions/45354001/nodejs-sequelize-delete-with-nested-select-query
- migrations. Generally speaking, anything but the simplest migrations are exceedingly hard to get right, as you have to go very low level when doing migrations. Syntax can be very different from regular DB operations.
- no way to do (non-raw) queries during migrations, e.g. to update fields based on other fields in a complex way?
- github.com/sequelize/cli/issues/862
- stackoverflow.com/questions/18742962/add-data-in-sequelize-migration-script
- stackoverflow.com/questions/38671483/sequelize-migration-update-model-after-updating-column-attributes
- stackoverflow.com/questions/38998397/can-i-use-sequelize-models-in-migration-scripts
- stackoverflow.com/questions/45286429/custom-query-on-sequelize-seeder
queryInterface.sequelize.modelscontains onlySequelizeMeta. Not sure why they have this limitation. - stackoverflow.com/questions/56043246/node-js-sequelize-no-primary-keys-when-migrating/56046101#56046101
- SQLite
changeColumnmigrations do on delete cascades of other tables. SQLite does not have change column statements, so they have to drop and recreate tables, but they don't temporarily remove cascades, so you lose data: stackoverflow.com/questions/62667269/sequelize-js-how-do-we-change-column-type-in-migration/70486686#70486686 - associations require full explicit index construction: stackoverflow.com/questions/39651853/how-to-create-join-table-with-foreign-keys-with-sequelize-or-sequelize-cli
- ability to iterate over a large result without blowing up memory and without using limit + offset (which is inneficient e.g. when looping over recursive queries). This is also known as cursor or streaming interfaces:E.g. the Python SQLite interface supports this just fine: stackoverflow.com/questions/29582736/python3-is-there-a-way-to-iterate-row-by-row-over-a-very-large-sqlite-table-wi
- stack overflow
- stackoverflow.com/questions/28787889/how-can-i-set-up-sequelize-js-to-stream-data-instead-of-a-promise-callback
- stackoverflow.com/questions/43964067/how-to-implement-cursor-pagination-using-sequelize
- stackoverflow.com/questions/57164242/perform-sequelize-findall-in-a-huge-array
- stackoverflow.com/questions/55191891/how-to-loop-through-result-in-sequelize generic loop
- issue tracker
- stack overflow
- empty
attributes: []breaks some nested queries: github.com/sequelize/sequelize/issues/16436 - does not expose a iteration API that supports large arrays?E.g. Python SQLite does: stackoverflow.com/questions/29582736/python3-is-there-a-way-to-iterate-row-by-row-over-a-very-large-sqlite-table-wi
To run examples on a specific database:All examples can be tested on all databases with:
./index.jsor./index.js l: SQLite./index.js p: PostgreSQL. You must manually create a database calledtmpand ensure that peer authentication works for it
cd sequelize
./testOverview of the examples:
- nodejs/sequelize/index.js: a bunch of basic examples
- nodejs/sequelize/update.js: This file is also where we are storing our expression-foo for now, e.g. how to do stuff like
col1 + col2. Such knowledge can however be used basically anywhere else however, e.g. inASorWHEREclauses, not just inUPDATE. - nodejs/sequelize/count.js: a simplified single-table count example. In practice, this will be usually done together with JOIN queries across multiple tables. Answers: stackoverflow.com/questions/22627258/how-does-group-by-works-in-sequelize/69896449#69896449
- nodejs/sequelize/date.js: automatic date typecasts
- nodejs/sequelize/like.js: LIKE
- nodejs/sequelize/camel_case.js: trying to get everything in the database camel cased, columns starting with lowercase, and tables starting with uppercase. The defaults documented on getting started documentation do uppercase foreign keys, and lowercase non-foreign keys. It's a mess.
- nodejs/sequelize/ignore_duplicates.js: ignore query on unique violation with
ignoreDuplicates: truewhich does SQLiteINSERT OR IGNORE INTOor PostgreSQLON CONFLICT DO NOTHING. Closely related Upsert versions:- Upsert
- nodejs/sequelize/upsert.js:
.upsertselects the conflict column automatically by unique columns. Both SQLite and PostgreSQL doINSERT INTO ON CONFLICT. PostgreSQL usesRETURNING, which was added too recently to SQLite: www.sqlite.org/lang_returning.html - nodejs/sequelize/update_on_duplicate.js:
.bulkCreate({}, { updateOnDuplicate: ['col1', col2'] }. Produces queries analogous to.upsert. This method is cool because it can upsert multiple columns at once. But it is annoying that you have to specify all fields to be updated one by one manually. - stackoverflow.com/questions/29063232/how-to-get-the-id-of-an-inserted-or-updated-record-in-sequelize-upsert/72092277#72092277
- stackoverflow.com/questions/55531860/sequelize-bulkcreate-updateonduplicate-for-postgresql
- Upsert
- nodejs/sequelize/inc.js: demonstrate the
incrementmethod. In SQLite, it produces a statement of type:UPDATE `IntegerNames` SET `value`=`value`+ 1,`updatedAt`='2021-11-03 10:23:45.409 +00:00' WHERE `id` = 3 - nodejs/sequelize/sync_alter.js: illustrates
Model.sync({alter: true})to modify a table definition, answers: stackoverflow.com/questions/54898994/bulkupdate-in-sequelize-orm/69044138#69044138 - nodejs/sequelize/truncate_key.js
- nodejs/sequelize/validation.js: is handled by a third-party library: github.com/validatorjs/validator.js. They then add a few extra validators on top of that.The
args: truething is explained at: stackoverflow.com/questions/58522387/unhandled-rejection-sequelizevalidationerror-validation-error-cannot-create-pr/70263032#70263032 - nodejs/sequelize/composite_index.js: stackoverflow.com/questions/34664853/sequelize-composite-unique-constraint
- nodejs/sequelize/indent_log.js: stackoverflow.com/questions/34664853/sequelize-composite-unique-constraint
- association examples:
- nodejs/sequelize/one_to_many.js: basic one-to-many examples.
- nodejs/sequelize/many_to_many.js: basic many-to-many examples, each user can like multiple posts. Answers: stackoverflow.com/questions/22958683/how-to-implement-many-to-many-association-in-sequelize/67973948#67973948
- ORDER BY include:
- nodejs/sequelize/many_to_many_custom_table.js: many-to-many example, but where we craft our own table which can hold extra data. In our case, users can like posts, but likes have a integer weight associated with them. Related threads:
- nodejs/sequelize/many_to_many_same_model.js: association between a model and itself: users can follow other users. Related:
- nodejs/sequelize/many_to_many_same_model_super.js
- nodejs/sequelize/many_to_many_super.js: "Super many to many": sequelize.org/master/manual/advanced-many-to-many.html This should not exist and shows how bad this library is for associations, you need all that boilerplate in order to expose certain relationships that aren't otherwise exposed by a direct
hasManywith implicit join table.
- nested includes to produce queries with multiple JOIN:
- nodejs/sequelize/nested_include.js: find all posts by users that a given user follows. Answers: stackoverflow.com/questions/42632943/sequelize-multiple-where-clause/68018083#68018083
- nodejs/sequelize/nested_include_super.js: like nodejs/sequelize/nested_include.js but with a super many to many. We should move this to nodejs/sequelize/many_to_many_super.js.
- two relationships between two specific tables: we need to use
as:to disambiguate them- nodejs/sequelize/many_to_many_double.js: users can both follow and like posts
- nodejs/sequelize/one_to_many_double.js: posts have the author and a mandatory reviewer
- hooks
- internals:
- nodejs/sequelize/common.js: common utilities used across examples, most notably:
- to easily setup different DBRM
- nodejs/sequelize/min_nocommon.js: to copy paste to Stack Overflow
- nodejs/sequelize/min.js: template for new exapmles in the folder
- nodejs/sequelize/common.js: common utilities used across examples, most notably:
Exampes under nodejs/sequelize/raw:
- nodejs/sequelize/raw/index.js: Sequelize raw query hello world. Ideally one should never use a raw query in a real project. We use raw examples mostly as a SQL tutorial under SQL example, and will not comment on them much further on this section.
No support:
Example with raw examples under nodejs/sequelize/raw/many_to_many.js
Pinned article: Introduction to the OurBigBook Project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Intro to OurBigBook
. Source. We have two killer features:
- topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculusArticles of different users are sorted by upvote within each article page. This feature is a bit like:
- a Wikipedia where each user can have their own version of each article
- a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
Figure 1. Screenshot of the "Derivative" topic page. View it live at: ourbigbook.com/go/topic/derivativeVideo 2. OurBigBook Web topics demo. Source. - local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
- to OurBigBook.com to get awesome multi-user features like topics and likes
- as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
Figure 3. Visual Studio Code extension installation.
Figure 4. Visual Studio Code extension tree navigation.
Figure 5. Web editor. You can also edit articles on the Web editor without installing anything locally.Video 3. Edit locally and publish demo. Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.Video 4. OurBigBook Visual Studio Code extension editing and navigation demo. Source. 
- Infinitely deep tables of contents:
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact