Home: go to the homepage U+2980 to U+29FF Miscellaneous Mathematical Symbols-B

# U+29E0Square with Contoured Outline

U+29E0 was added in Unicode version 3.2 in 2002. It belongs to the block U+2980 to U+29FF Miscellaneous Mathematical Symbols-B in the U+0000 to U+FFFF Basic Multilingual Plane.

This character is a Math Symbol and is commonly used, that is, in no specific script. The character is also known as D'Alembertian.

The glyph is not a composition. It has no designated width in East Asian texts. In bidirectional text it acts as Other Neutral. When changing direction it is not mirrored. The word that U+29E0 forms with similar adjacent characters prevents a line break inside it.

In special relativity, electromagnetism and wave theory, the d'Alembert operator (denoted by a box: $◻$), also called the d'Alembertian, wave operator, box operator or sometimes quabla operator (cf. nabla symbol) is the Laplace operator of Minkowski space. The operator is named after French mathematician and physicist Jean le Rond d'Alembert.

In Minkowski space, in standard coordinates (t, x, y, z), it has the form

Here ${\nabla }^{2}:=\Delta$ is the 3-dimensional Laplacian and ημν is the inverse Minkowski metric with

${\eta }_{00}=1$, ${\eta }_{11}={\eta }_{22}={\eta }_{33}=-1$, ${\eta }_{\mu \nu }=0$ for $\mu \ne \nu$.

Note that the μ and ν summation indices range from 0 to 3: see Einstein notation.

(Some authors alternatively use the negative metric signature of (− + + +), with ${\eta }_{00}=-1,\phantom{\rule{thickmathspace}{0ex}}{\eta }_{11}={\eta }_{22}={\eta }_{33}=1$.)

Lorentz transformations leave the Minkowski metric invariant, so the d'Alembertian yields a Lorentz scalar. The above coordinate expressions remain valid for the standard coordinates in every inertial frame.

## Representations

System Representation
10720
UTF-8 E2 A7 A0
UTF-16 29 E0
UTF-32 00 00 29 E0
URL-Quoted %E2%A7%A0
HTML hex reference &#x29E0;
Wrong windows-1252 Mojibake â§
alias D'Alembertian

## Complete Record

Property Value
Age (age) 3.2 (2002)
Unicode Name (na) SQUARE WITH CONTOURED OUTLINE
Unicode 1 Name (na1)
Block (blk) Miscellaneous Symbols
General Category (gc) Math Symbol
Script (sc) Common
Bidirectional Category (bc) Other Neutral
Combining Class (ccc) Not Reordered
Decomposition Type (dt) none
Decomposition Mapping (dm) Square with Contoured Outline
Lowercase (Lower)
Simple Lowercase Mapping (slc) Square with Contoured Outline
Lowercase Mapping (lc) Square with Contoured Outline
Uppercase (Upper)
Simple Uppercase Mapping (suc) Square with Contoured Outline
Uppercase Mapping (uc) Square with Contoured Outline
Simple Titlecase Mapping (stc) Square with Contoured Outline
Titlecase Mapping (tc) Square with Contoured Outline
Case Folding (cf) Square with Contoured Outline
ASCII Hex Digit (AHex)
Alphabetic (Alpha)
Bidi Control (Bidi_C)
Bidi Mirrored (Bidi_M)
Composition Exclusion (CE)
Case Ignorable (CI)
Changes When Casefolded (CWCF)
Changes When Casemapped (CWCM)
Changes When NFKC Casefolded (CWKCF)
Changes When Lowercased (CWL)
Changes When Titlecased (CWT)
Changes When Uppercased (CWU)
Cased (Cased)
Full Composition Exclusion (Comp_Ex)
Default Ignorable Code Point (DI)
Dash (Dash)
Deprecated (Dep)
Diacritic (Dia)
Emoji Modifier Base (EBase)
Emoji Component (EComp)
Emoji Modifier (EMod)
Emoji Presentation (EPres)
Emoji (Emoji)
Extender (Ext)
Extended Pictographic (ExtPict)
FC NFKC Closure (FC_NFKC) Square with Contoured Outline
Grapheme Cluster Break (GCB) Any
Grapheme Base (Gr_Base)
Grapheme Extend (Gr_Ext)
Hex Digit (Hex)
Hyphen (Hyphen)
ID Continue (IDC)
ID Start (IDS)
IDS Binary Operator (IDSB)
IDS Trinary Operator and (IDST)
IDSU (IDSU) 0
ID_Compat_Math_Continue (ID_Compat_Math_Continue) 0
ID_Compat_Math_Start (ID_Compat_Math_Start) 0
Ideographic (Ideo)
InCB (InCB) None
Indic Mantra Category (InMC)
Indic Positional Category (InPC) NA
Indic Syllabic Category (InSC) Other
Jamo Short Name (JSN)
Join Control (Join_C)
Logical Order Exception (LOE)
Math (Math)
Noncharacter Code Point (NChar)
NFC Quick Check (NFC_QC) Yes
NFD Quick Check (NFD_QC) Yes
NFKC Casefold (NFKC_CF) Square with Contoured Outline
NFKC Quick Check (NFKC_QC) Yes
NFKC_SCF (NFKC_SCF) Square with Contoured Outline
NFKD Quick Check (NFKD_QC) Yes
Other Alphabetic (OAlpha)
Other Default Ignorable Code Point (ODI)
Other Grapheme Extend (OGr_Ext)
Other ID Continue (OIDC)
Other ID Start (OIDS)
Other Lowercase (OLower)
Other Math (OMath)
Other Uppercase (OUpper)
Prepended Concatenation Mark (PCM)
Pattern Syntax (Pat_Syn)
Pattern White Space (Pat_WS)
Quotation Mark (QMark)
Regional Indicator (RI)
Sentence Break (SB) Other
Soft Dotted (SD)
Sentence Terminal (STerm)
Terminal Punctuation (Term)
Unified Ideograph (UIdeo)
Variation Selector (VS)
Word Break (WB) Other
White Space (WSpace)
XID Continue (XIDC)
XID Start (XIDS)
Expands On NFC (XO_NFC)
Expands On NFD (XO_NFD)
Expands On NFKC (XO_NFKC)
Expands On NFKD (XO_NFKD)
Bidi Paired Bracket (bpb) Square with Contoured Outline
Bidi Paired Bracket Type (bpt) None
East Asian Width (ea) neutral
Hangul Syllable Type (hst) Not Applicable
ISO 10646 Comment (isc)
Joining Group (jg) No_Joining_Group
Joining Type (jt) Non Joining
Line Break (lb) Alphabetic
Numeric Type (nt) none
Numeric Value (nv) not a number
Simple Case Folding (scf) Square with Contoured Outline
Script Extension (scx)
Vertical Orientation (vo) R