# What is renormalization group?

**Asked by: Patrick Williams**| Last update: 18 June 2021

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In theoretical physics, the term renormalization group refers to a formal apparatus that allows systematic investigation of the changes of a physical system as viewed at different scales.

View full answerLikewise, people ask, Why is it called renormalization group?

All Answers (5) The transformations underlying a

**renormalization group**scheme share the properties of the elements of a

**group**. Hence the name.

Beside the above, What is renormalization group equation?. An exact

**renormalization group equation**(ERGE) is one that takes irrelevant couplings into account. ... The smoothness of the cutoff, however, allows us to derive a functional differential

**equation**in the cutoff scale Λ. As in Wilson's approach, we have a different action functional for each cutoff energy scale Λ.

Also, What is renormalization theory?

**Renormalization**, the procedure in quantum field

**theory**by which divergent parts of a calculation, leading to nonsensical infinite results, are absorbed by redefinition into a few measurable quantities, so yielding finite answers.

Why the renormalization group is a good thing?

They are efficient calculational methods (for Feynman diagrams). ... They completely hide the physics of many scales. These methods are hard to follow in detail for physicists without quantum field theoretical training. "

**21 related questions found**

### Is renormalization group a group?

Is the "**renormalization group" a group**? The answer is "no".

### What is renormalization scale?

The charge of the electron, say, would be defined in terms of a quantity measured at a specific kinematic **renormalization** point or subtraction point (which will generally have a characteristic energy, called the **renormalization scale** or simply the energy **scale**).

### Is there a quantum theory of gravity?

**Quantum gravity** (QG) is a field of theoretical **physics** that seeks to describe **gravity** according to the principles of **quantum mechanics**, and where **quantum** effects cannot be ignored, such as in the vicinity of black holes or similar compact astrophysical objects where the effects of **gravity** are strong, such as neutron ...

### Is deep learning an RG flow?

**Deep learning** performs a sophisticated coarse graining. ... Since coarse graining is a key ingredient of the **renormalization group** (**RG**), **RG** may provide a useful theoretical framework directly relevant to **deep learning**.

### Why gravity is non renormalizable?

Gluons carry color charge and couple to themselves, yet QCD is **renormalizable**. ... In general, **non**-abelian gauge theories are **renormalizable** despite the fact that their force-carriers couple to each other. The problem with **gravity** is that its coupling constant G is **not** dimensionless (in units where ℏ and c are 1).

### Is gravity understood?

We don't really know. We can define what it is as a field of influence, because we know how it operates in the universe. And some scientists think that it is made up of particles called gravitons which travel at the speed of light.

### Who invented quantum gravity?

Giovanni Amelino-Camelia: physicist who developed the idea of doubly special relativity, and founded **Quantum**-**Gravity** phenomenology. Abhay Ashtekar: **inventor** of the Ashtekar variables, one of the founders of loop **quantum gravity**.

### Is gravity a wave?

Gravitational **waves** are 'ripples' in space-time caused by some of the most violent and energetic processes in the Universe. Albert Einstein predicted the existence of gravitational **waves** in 1916 in his general theory of relativity. ... Note that gravitational **waves** themselves are invisible.

### What frequency is gravity?

The **gravitational** wave spectrum

In general, **gravitational** wave **frequencies** are much lower than those of the electromagnetic spectrum (a few thousand hertz at most, compared to some 10^{16} to 10^{19} Hz for X-rays).

### Has a graviton been found?

One consequence of that: while scientists know of particles associated with the strong, weak and electromagnetic forces, they **have** yet to discover a particle of gravity, or **graviton**.

### How fast is gravity?

The best results, at the present time, tell us that the speed of **gravity** is between 2.993 × 10^8 and 3.003 × 10^8 meters per second, which is an amazing confirmation of General Relativity and a terrible difficulty for alternative theories of **gravity** that don't reduce to General Relativity!

### How many dimensions are there?

The world as we know it has three **dimensions** of space—length, width and depth—and one **dimension** of time. But **there's** the mind-bending possibility that **many** more **dimensions** exist out **there**. According to string theory, one of the leading physics model of the last half century, the universe operates with 10 **dimensions**.

### Can gravity be entangled?

We have shown that two nearby masses—both trapped and released—**can** become **entangled** via **gravitational** interaction.

### Is time a quantum?

While **time** is a continuous quantity in both standard **quantum** mechanics and general relativity, many physicists have suggested that a discrete model of **time** might work, especially when considering the combination of **quantum** mechanics with general relativity to produce a theory of **quantum** gravity.