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Apr 26, 2020, 6:05:49 PM4/26/20

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Some journals require upright Greek letters for constants as opposed to

variables, for example $\upi$ when used to denote 3.14159... as opposed

to a variable ($\pi$ is sometimes used to denote parallax in astronomy,

for instance). (Some journals define \upi as "upright pi", \upi as

"upright i", and so on.)

I certainly agree that LABELS should be upright (though they are usually

Latin not Greek) and not italic to distinguish them from variables, e.g.

$T_{mathrm{eff}}$ for effective temperature or $\rho_{textrm{g}}$ for

gas density, say, as opposed to $G_{\mu\nu}$ where $\mu$ and $\nu$ are

not constants but variables.

And it is not just Greek letters. For example, e for the Euler number

or i for the square root of -1 should also not be in math italic, to

distinguish them from variables. I tend to agree with that as well.

Also, units should be upright, e.g. 5 m and not $5m$ for 5 metres.

On the other hand, I have never seen the gravitational constant $G$,

which is even by definition a constant and not a variable, written

upright. Ditto for the Hubble constant $H$ and so on.

Or is there a difference between mathematical constants and physical

constants?

Perhaps because standard (La)TeX provides Greek letters only in math

italic, upright Greek letters are less common than upright Latin

letters, even when used in the same way (labels, units, symbols which

are not variables).

When writing for a specific journal, one usually has to follow the house

style. However, if there is no rule, I prefer to do what is generally

deemed to be correct. What is generally deemed to be correct here?

variables, for example $\upi$ when used to denote 3.14159... as opposed

to a variable ($\pi$ is sometimes used to denote parallax in astronomy,

for instance). (Some journals define \upi as "upright pi", \upi as

"upright i", and so on.)

I certainly agree that LABELS should be upright (though they are usually

Latin not Greek) and not italic to distinguish them from variables, e.g.

$T_{mathrm{eff}}$ for effective temperature or $\rho_{textrm{g}}$ for

gas density, say, as opposed to $G_{\mu\nu}$ where $\mu$ and $\nu$ are

not constants but variables.

And it is not just Greek letters. For example, e for the Euler number

or i for the square root of -1 should also not be in math italic, to

distinguish them from variables. I tend to agree with that as well.

Also, units should be upright, e.g. 5 m and not $5m$ for 5 metres.

On the other hand, I have never seen the gravitational constant $G$,

which is even by definition a constant and not a variable, written

upright. Ditto for the Hubble constant $H$ and so on.

Or is there a difference between mathematical constants and physical

constants?

Perhaps because standard (La)TeX provides Greek letters only in math

italic, upright Greek letters are less common than upright Latin

letters, even when used in the same way (labels, units, symbols which

are not variables).

When writing for a specific journal, one usually has to follow the house

style. However, if there is no rule, I prefer to do what is generally

deemed to be correct. What is generally deemed to be correct here?

May 15, 2020, 11:09:32 PM5/15/20

to

On 2020-04-27 00:05, Phillip Helbig (undress to reply) wrote:

> Some journals require upright Greek letters for constants as opposed to

> variables, for example $\upi$ when used to denote 3.14159... as opposed

> to a variable ($\pi$ is sometimes used to denote parallax in astronomy,

> for instance). (Some journals define \upi as "upright pi", \upi as

> "upright i", and so on.)

...
> Some journals require upright Greek letters for constants as opposed to

> variables, for example $\upi$ when used to denote 3.14159... as opposed

> to a variable ($\pi$ is sometimes used to denote parallax in astronomy,

> for instance). (Some journals define \upi as "upright pi", \upi as

> "upright i", and so on.)

> Or is there a difference between mathematical constants and physical

> constants?

The principle probably comes from pure mathematics, but even there,
> constants?

historically, they have not been available, just as well certain styles,

such as bold italic, for the simple reason that it was expensive in led

typesetting to keep them. Some journals would though have them, and one

could mark up the manuscript to get the right one.

Unicode changed that by adding those as characters (code points), in

addition adding some styles that are not properly semantic, like sans

serif and monospace variations. (The sans serif style is used for

tensors by some engineers, but I have found no example in mathematics,

physics or computer science of that.)

[[Mod. note -- Checking a few general-relativity textbooks, I see that

Misner, Thorne, & Wheeler "Gravitation" (W.H. Freeman, 1973) uses sans

serif for tensors and differential forms, but none of the other books

I checked do this.

-- jt]]

So when those are available, one can experiment with adhering to this

principle, upright for constants and italic/slanted for variables.

In some cases it may not be immediately clear what to use: Unicode

unifies the upright style with the original language letters.

TeX, by contrast, translates them automatically to italic in math mode.

For Greek, it only has the slanted styles, and in addition not the

uppercase letters that look like the Latin.

> Perhaps because standard (La)TeX provides Greek letters only in math

> italic, upright Greek letters are less common than upright Latin

> letters, even when used in the same way (labels, units, symbols which

> are not variables).

file, and the fastest way to do that, both to implement and use, I found

is to use text substitutions. Then the LaTeX unicode math package was

insufficient, so I switched to ConTeXt.

> When writing for a specific journal, one usually has to follow the house

> style. However, if there is no rule, I prefer to do what is generally

> deemed to be correct. What is generally deemed to be correct here?

May 23, 2020, 2:10:06 PM5/23/20

to

On 2020-05-16 05:09, Mod wrote:

> Unicode changed that by adding those as characters (code points), in

> addition adding some styles that are not properly semantic, like sans

> serif and monospace variations. (The sans serif style is used for

> tensors by some engineers, but I have found no example in mathematics,

> physics or computer science of that.)

>

> [[Mod. note -- Checking a few general-relativity textbooks, I see that

> Misner, Thorne, & Wheeler "Gravitation" (W.H. Freeman, 1973) uses sans

> serif for tensors and differential forms, but none of the other books

> I checked do this.

> -- jt]]

They use bold sans-serif when not having indices, but switches to
> Unicode changed that by adding those as characters (code points), in

> addition adding some styles that are not properly semantic, like sans

> serif and monospace variations. (The sans serif style is used for

> tensors by some engineers, but I have found no example in mathematics,

> physics or computer science of that.)

>

> [[Mod. note -- Checking a few general-relativity textbooks, I see that

> Misner, Thorne, & Wheeler "Gravitation" (W.H. Freeman, 1973) uses sans

> serif for tensors and differential forms, but none of the other books

> I checked do this.

> -- jt]]

non-bold serif, that is, plain italic, when having indices on the same

object. In mathematics, like in differential geometry, one uses serifs

and not switching styles, like between plain and bold, allowing the

styles to be used for more different types of objects objects.

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