# What Are Multipoles? Answers & More

• kyle_soule
In summary, a multipole refers to the procedures used to solve problems involving long-range Coulombic forces by taking advantage of symmetry and dividing the space into grids. This allows for more efficient calculation of pairwise interactions within a system. Additionally, the concept of a graviton, which has an exclusively attractive force and emulates a quadrupole, is often used in discussions of multipole algorithms.
kyle_soule
What is a multipole? or, perhaps, more appropriately, what are multipoles?

The whole subject of multipole algorithms is infinitely unclear to me, so literally any information will be helpful.

if this can help...

http://www-aix.gsi.de/~weick/gico/gicohow/node17.html

http://www.mpip-mainz.mpg.de/~gelessus/pubs/pub4.html

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As Sulaiman already provided some good links on the basic idea of what a multipole is, here's a bit of the rest...

Multipole algorithms/methods generally refer to the procedures used to solve problems where you have to find the long-range Coulombic forces from a group of charges via a multipole expansion of the potential. In a more general sense, it's a way to determine pairwise interactions by essentially taking advantage of the symmetry of the problem, dividing the space into grids, and then first calculating within each grid and more or less summing up their subtotals. So, after a fashion, instead of calculating each and every pairwise interaction of a system, you only calculate the pairwise interactions explicitly within the grid so as to save yourself time and CPU/memory capacity.

Added after edit: Sorry about that, Sulaiman. :) I've fixed it now.

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The graviton, having exclusively attractive force of infinite extent, is supposed to emulate a quadrupole in order to generate gravitational waves.

Can you please call me Sulaiman...thanks

Originally posted by Loren Booda
The graviton, having exclusively attractive force of infinite extent, is supposed to emulate a quadrupole in order to generate gravitational waves.

I was actually wondering what a multipole was because of gravitons Funny you would use that example.

## 1. What are multipoles?

Multipoles are mathematical representations of the distribution of electric charge or magnetic moments in a system. They are used to describe the strength and direction of electric or magnetic fields in a given space.

## 2. How are multipoles calculated?

Multipoles are calculated by expanding the potential of the system into a series of terms, with each term representing a different order of multipole moment. These terms are derived from the Cartesian coordinates of the charges or magnetic moments in the system.

## 3. What is the significance of multipoles?

Multipoles are important in understanding the behavior of electric and magnetic fields in complex systems. They allow for a more precise description of the distribution of charges or magnetic moments, and can be used to calculate the potential and field at any point in space.

## 4. Can multipoles be negative?

Yes, multipoles can have negative values. This occurs when the distribution of charges or magnetic moments is not symmetrical, resulting in a negative value for the corresponding multipole moment.

## 5. How are multipoles used in practical applications?

Multipoles have a wide range of uses in various scientific fields, including electromagnetism, astrophysics, and molecular biology. They are used in the design of electronic devices, the study of gravitational and magnetic fields in space, and in determining the structure of molecules and proteins.

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