Some journals require upright Greek letters for constants as opposed to=20 variables, for example $\upi$ when used to denote 3.14159... as opposed=20
to a variable ($\pi$ is sometimes used to denote parallax in astronomy,=20 for instance). (Some journals define \upi as "upright pi", \upi as=20 "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.=20
And it is not just Greek letters. For example, e for the Euler number=20
or i for the square root of -1 should also not be in math italic, to=20 distinguish them from variables. I tend to agree with that as well. =20 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 $G$,=20
which is even by definition a constant and not a variable, written=20 upright. Ditto for the Hubble constant $H$ and so on.=20
Or is there a difference between mathematical constants and physical=20 constants?
Perhaps because standard (La)TeX provides Greek letters only in math=20 italic, upright Greek letters are less common than upright Latin=20
letters, even when used in the same way (labels, units, symbols which=20
are not variables).
When writing for a specific journal, one usually has to follow the house=20 style. However, if there is no rule, I prefer to do what is generally=20 deemed to be correct. What is generally deemed to be correct here? =20
These are great journals since they care for century-old good practice
in microtypography.
The rules are that mathematical constants like i, e, pi etc. are set
upright. The same holds for operators like the differential d. All units
have to be set upright. Physical constants (even those which are
exactly defined in the new SI like c, h, \hbar, etc.) however have to be
set in italics.
The Newton gravitational constant is also to be set in
italics (it's not even a fixed value in the SI for understandable
reasons).
All variable quantities are set in italics.
The only exception are
capital greek letters (in the German and the Anglo-Saxxon tradition; the French also set these letters in italics).
The same holds for indices,
which are variable (e.g., running over 1 to 3 in 3D in Euclidean or from
0 to 3 in Minkowski/GR vector calculus). In contradistinction to that if
the index is a descriptor like $k_{\text{B}}$, where the B stands for Boltzmann and is not variable, it should be set upright.
In LaTeX there are extra packages for a full upright Greek math
alphabeth (it's also included in the exceptionally good font package mathdesign, where you have the choice full math alphabeths in very nice
fonts like Garamond, Utopia, Charter).
In article <hgl318Fcvr0U1@mid.dfncis.de>, Hendrik van Hees <hees@fias.uni-frankfurt.de> writes:
These are great journals since they care for century-old good practiceRight; that seems to be what the journals who care about those things
in microtypography.
The rules are that mathematical constants like i, e, pi etc. are set
upright. The same holds for operators like the differential d. All units
have to be set upright. Physical constants (even those which are
exactly defined in the new SI like c, h, \hbar, etc.) however have to be
set in italics.
do.
The Newton gravitational constant is also to be set inTrue, but it is certainly not a variable in the mathematical sense.
italics (it's not even a fixed value in the SI for understandable
reasons).
All variable quantities are set in italics.My question is really why mathematical, but not physical, constants
should be upright. In maths is clear: italic means variable, upright
means constant or label or operator or unit. In physics, italic means variable OR constant, upright means label or operator or unit.
The only exception areWhat is a common example of a capital Greek letter being used as a
capital greek letters (in the German and the Anglo-Saxxon tradition; the
French also set these letters in italics).
variable? Perhaps the Gamma factor in special relativity? (Zel'dovich
used Delta = 1 - 1/(1+z) for the cosmological redshift, but that has
gone out of fashion.)
The same holds for indices,Right; it is a label.
which are variable (e.g., running over 1 to 3 in 3D in Euclidean or from
0 to 3 in Minkowski/GR vector calculus). In contradistinction to that if
the index is a descriptor like $k_{\text{B}}$, where the B stands for
Boltzmann and is not variable, it should be set upright.
In LaTeX there are extra packages for a full upright Greek mathYes, I've used some of those. At least in some cases, the upright
alphabeth (it's also included in the exceptionally good font package
mathdesign, where you have the choice full math alphabeths in very nice
fonts like Garamond, Utopia, Charter).
letters have new commands, since the usual ones are used for the italic characters. This makes it a pain when recycling something like a
complicated formula. In general, I try to have all differences between journals which are not handled by the corresponding LaTeX class handled
by my own macros. So first I load my own macros, which are my
defaults, then journal-specific macro packages which redefine things
which differ from my defaults. (That applies to many things, such as spelling, punctuation, italicization (or not) of foreign expressions,
forms of dashes, and so on. Using \newcommand, \renewcommand, and \providecommand gives the necessary flexibility (e.g. one can define something (sensibly, with the same definition) if it hasn't been defined
by the class, otherwise use the definition from the class).
So basically, my question is what should the defaults be, but it seems
that you agree with the great journals, so I'll go that route.
But what is the origin of the difference between mathematical and
physical constants and for the exception to set capital Greek variables upright (but not in France)?
Of course, $W$ is the variable for energy, W the unit watt, $m$ the
variable for mass, m the unit meter, and so on. Could that be the
reason?
What about alpha, beta, and gamma rays? Should probably be upright?
Of course, after all these are conventions and often just a tradition.
Why the physical fundamental constants are in italics and not upright
is something I'm also puzzled about, but on the other hand, while mathematical constants are really constant and what they are, the
values of the fundamental constants depend on the choice of the
units.
E.g., with the official change to the new SI the magnetic
field constant became a derived quantity with an error, while before
it was defined as an exact quantity by the old definition of the
Ampere (two infinite straight wires...).
Now it's to be measured
based on the fixed value of the elementary charge and the definition
of the second in terms of the Cesium hyperfine splitting frequency.
Last but not least, not all journals follow these rules. Sometimes
they even don't like to set the differential d upright.
If you use Word, it's impossible to get a good microtypography
anyway. There you can only hope that the journal transforms it
into a readable text ;-)).
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