# What symbol is this?

I need the command to display this symbol in LaTeX or, at least, its name.

I guess it’s from some kind of a mathematical or informatics discipline. I saw it in article called “A comparison of collapsed Bayesian methods for probabilistic finite automata”. Actually, I have no idea what it is all about: I just started learning LaTeX and I have to copy this article. This symbol is used just as if it is a casual letter like x or y. The line which includes it is,

Input : a(this symbol), N, BurnInTime, SamplingNum, Period

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Welcome to tex.sx! Where did you see this symbol, what does it mean, what field of study does it belong to? – doncherry Jul 2 '14 at 13:24
I have never seen this symbol before. Have you checked the comprehensive symbol list already? mirrors.ctan.org/info/symbols/comprehensive/symbols-a4.pdf – Christian Hupfer Jul 2 '14 at 13:29
possible duplicate of How to look up a symbol or identify a math alphabet? – Martin Schröder Jul 2 '14 at 14:54
@MartinSchröder If it is not possible to find via tools in that question we tend to leave these open, with emphasis on tend to – percusse Jul 2 '14 at 15:04
@samcarter detexify.kirelabs.org didn't find the letter (or symbol) and that I tried to draw it as best I could. – skpblack Jul 2 '14 at 15:28

To me this looks like a blackboard bold lowercase a. Specifically, it looks like the lowercase a from the bbold font.

For blackboard bold capitals you can use the \mathbb macro provided by the amsfonts or amssymb packages. But $\mathbb{a}$ gives a backwards G.

Instead, you need to load the whole bbold font. Here's a quick snippet to do that.

\documentclass{article}
\DeclareSymbolFont{bbold}{U}{bbold}{m}{n}
\DeclareSymbolFontAlphabet{\mathbbold}{bbold}

\begin{document}
$\mathbbold{a}$
\end{document}


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good sleuthing. i would never have gotten this without help. i'm much more accustomed to the shape shown in the unicode charts at U+1D552. – barbara beeton Jul 2 '14 at 14:23
@barbarabeeton: Thanks. It was a hunch and some quick googling. Knowing that it was used as a variable instead of a binary operation or relation was a hint that it might be a letter of some kind. – Matthew Leingang Jul 2 '14 at 14:37
@MatthewLeingang i can't get a a letter with good quality, if i run your code i get a a pixelled, very different to this test. If you can help me! – skpblack Jul 2 '14 at 14:47
@skpblack: Hm, it's possible your installation doesn't have the fonts at the size you want? What does the log file say? – Matthew Leingang Jul 2 '14 at 14:48
Something like LaTeX Font Info: Try loading font information for U+bbold on input line 9. ("C:\Program Files\LaTeX\MiKTeX 2.9\tex\latex\jknappen\ubbold.fd" File: ubbold.fd 1996/01/01 Blackboard Bold Font Definition File (jk) ) [1 – skpblack Jul 2 '14 at 14:55

I think Matthew is right, there is the pdffonts output from the article Barbara linked to

name                                 type              emb sub uni object ID
------------------------------------ ----------------- --- --- --- ---------
Times-Roman                          Type 1C           yes no  no     763  0
Times-Bold                           Type 1C           yes no  no     764  0
MTSYB                                Type 1C           yes no  yes    765  0
MTSYN                                Type 1C           yes no  yes    771  0
MarVoSym                             Type 1C           yes no  yes    778  0
Times-Italic                         Type 1C           yes no  no     459  0
MTMI                                 Type 1C           yes no  yes    463  0
BBOLD5                               Type 1C           yes no  yes    480  0
BBOLD7                               Type 1C           yes no  yes    475  0
MTEX                                 Type 1C           yes no  yes    470  0
Courier                              Type 1C           yes no  no     491  0
MSBM10                               Type 1C           yes no  yes    500  0

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