FrobeniusAutomorphism
✖
FrobeniusAutomorphism
gives the value of the Frobenius automorphism at the finite field element a.
gives the value of the kth functional power of the Frobenius automorphism at a.
Details

- For a finite field
with characteristic
, the Frobenius automorphism is given by
.
- All finite field automorphisms are functional powers of the Frobenius automorphism.
- The number of different field automorphisms of
is equal to the extension degree of
over
.
- Any field automorphism
satisfies equations
and
.
- If n is the degree of the MinimalPolynomial f of an element a of
, then Table[FrobeniusAutomorphism[a,k],{k,n}] gives all the roots of f in
.
Examples
open allclose allBasic Examples (1)Summary of the most common use cases
Represent a finite field with characteristic and extension degree
:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-o809yt

Compute the value of the Frobenius automorphism at an element of the field:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-gwq297


https://wolfram.com/xid/0vu3wx0nj254f057ce0-djcrnz

The third functional power of the Frobenius automorphism:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-vpp8c


https://wolfram.com/xid/0vu3wx0nj254f057ce0-7ay06

Scope (1)Survey of the scope of standard use cases
Compute the value of the Frobenius automorphism at an element of a finite field:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-cx03mi


https://wolfram.com/xid/0vu3wx0nj254f057ce0-l52b8q

Conjugates of a are roots of the minimal polynomial of a:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-kiesl

Applications (1)Sample problems that can be solved with this function
Compute the minimal polynomial of an element of a finite field:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-1pb6k

The minimal polynomial of is the product of
over all conjugates
of
:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-dcabog

Convert to integer coefficients:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-ngey2

Compare with the result obtained using the built-in MinimalPolynomial:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-48d8j

Properties & Relations (5)Properties of the function, and connections to other functions
Frobenius automorphism is a field automorphism:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-d33o2a


https://wolfram.com/xid/0vu3wx0nj254f057ce0-ehms77


https://wolfram.com/xid/0vu3wx0nj254f057ce0-gvurha

For a finite field with characteristic
, the Frobenius automorphism is given by
:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-gn6eg5


https://wolfram.com/xid/0vu3wx0nj254f057ce0-voiz9

All finite field automorphisms are functional powers of the Frobenius automorphism:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-i1siun

Use FiniteFieldEmbedding to find an automorphism of :

https://wolfram.com/xid/0vu3wx0nj254f057ce0-bwlb2j

Identify the functional power of the Frobenius automorphism that gives the same mapping:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-n4s2fm


https://wolfram.com/xid/0vu3wx0nj254f057ce0-eul20t

The number of different field automorphisms of is equal to the extension degree of
over
:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-qa4ju


https://wolfram.com/xid/0vu3wx0nj254f057ce0-buhqp2


https://wolfram.com/xid/0vu3wx0nj254f057ce0-pyk0vz

Compute all conjugates of a finite field element a:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-carevw

The absolute trace of a is equal to the sum of conjugates:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-kxn2o7

Use FiniteFieldElementTrace to compute the absolute trace:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-c14e4b

The absolute norm of a is equal to the product of conjugates:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-ubopn

Use FiniteFieldElementNorm to compute the absolute norm:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-z1ad7

The conjugates are roots of MinimalPolynomial[a]:

https://wolfram.com/xid/0vu3wx0nj254f057ce0-bgtnzk

Wolfram Research (2023), FrobeniusAutomorphism, Wolfram Language function, https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html.
Text
Wolfram Research (2023), FrobeniusAutomorphism, Wolfram Language function, https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html.
Wolfram Research (2023), FrobeniusAutomorphism, Wolfram Language function, https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html.
CMS
Wolfram Language. 2023. "FrobeniusAutomorphism." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html.
Wolfram Language. 2023. "FrobeniusAutomorphism." Wolfram Language & System Documentation Center. Wolfram Research. https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html.
APA
Wolfram Language. (2023). FrobeniusAutomorphism. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html
Wolfram Language. (2023). FrobeniusAutomorphism. Wolfram Language & System Documentation Center. Retrieved from https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html
BibTeX
@misc{reference.wolfram_2025_frobeniusautomorphism, author="Wolfram Research", title="{FrobeniusAutomorphism}", year="2023", howpublished="\url{https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html}", note=[Accessed: 04-April-2025
]}
BibLaTeX
@online{reference.wolfram_2025_frobeniusautomorphism, organization={Wolfram Research}, title={FrobeniusAutomorphism}, year={2023}, url={https://reference.wolfram.com/language/ref/FrobeniusAutomorphism.html}, note=[Accessed: 04-April-2025
]}