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HEP-TH-9502100 t-curren e Thirring mo del is equiv acult [email protected] In the pro cess of the b osonization e fermion . , Chiba 263, Japan of y hi Kondo ysics, F e-mail: k -dimensional massiv Abstract D t out the imp ortance of the gauge-in ersit ebruary 1995, hep-th/9502100 e Thirring mo del ery massiv Kei-Ic ho ol of Science and T tofPh e p oin ulation of the Thirring mo del as a gauge theory teraction of the curren Massiv e Thirring mo del is mapp ed to the Maxw Bosonization and Dualit Chiba Univ e free scalar eld theory Departmen & Graduate Sc CHIBA-EP-88, F tion to the case of v ulation. Starting from a form y atten dimensional massiv theory and that the (1+1)-dimensional massiv dimensions. Up to the next-to-leading order of 1 to the massiv pa of the Thirring mo del, w form 2) with four-fermion in consider the b osonization of the provided byCERNDocumentServer brought toyouby CORE
1 Intro duction and main results
Recently the Thirring mo del [1, 2 ] was reformulated as a gauge theory and
was identi ed with a gauge- xed version of the corresp onding gauge theory
byintro ducing the Stuc kelb erg eld in addition to the auxiliary vector eld
A which is in that formulation identi ed with the massless gauge eld [3, 4 ].
This is a consequence of the general formalism for the constrained system by
Batalin and Fradkin [5]. This gives the general pro cedure by which the system
with the second class constraintisconverted to that with the rst class one
and the new eld which is necessary to complete this pro cedure is called the
Batalin-Fradkin eld [6]. In the massive gauge theory the Batalin-Fradkin eld
is nothing but the well-known Stuc kelb erg eld as shown in [7]. By maintaining
the manifest gauge symmetry, controversy among the pap ers [8, 9 , 10 , 11 , 12]
will b e resolved as emphasized in [3].
We consider the mapping from quantum eld theory of interacting fermions
onto an equivalent theory of interacting b osons. In this pap er such an equiva-
lent b osonic theory to the original massive Thirring mo del is obtained starting
from the formulation of the D -dimensional Thirring mo del (D 2) as a gauge
theory. This is a kind of b osonization. Esp ecially, in this pap er we consider
the large bare fermion mass limit m 1, in (2+1) and (1+1) dimensional
cases.
In a sp ecial case of (2+1)-dimensions, we show that, up to the next-to-
leading order in the inverse bare fermion mass, 1=m, the (2+1)-dimensional
massive Thirring model is equivalent to the Maxwel l-Chern-Simons theory, the
topological ly massive U (1) gauge theory. This equivalence in three dimensions
has b een shown, to the lowest order in 1=m,byFradkin and Schap osnik [14].
However we think that their treatment is unsatisfactory in the following p oints.
1. The original Thirring mo del has no gauge symmetry. Nevertheless the
equivalent b osonic theory, the Maxwell-Chern-Simons theory, has U (1)
gauge symmetry. Where do es this gauge symmetry come from?
2. The master Lagrangian (which is called the interp olating Lagrangian in
[14]) of Deser and Jackiw [15] was suddenly intro duced without notice
as a device which is needed to show this equivalence. However the origin
of the master Lagrangian was never shown.
3. The master Lagrangian is invariant under the indep endent gauge trans-
formations for the auxiliary vector eld A and another vector eld. In
integrating out another vector eld in the master Lagrangian, they had
to intro duce the gauge- xing term ad ho c.
We resolve these problems by starting from the gauge-invariant or more pre-
cisely the BRS-invariant formulation of the Thirring mo del. Our approachis
more direct than theirs and is able to derive the equivalent Lagrangian to the
interp olating Lagrangian as a natural consequence (in an intermediate step) 2
of b osonization and determines de nitely the pro cedure which is needed to x
the gauge invariance app earing in the master Lagrangian [15 ]. Our metho d
may b e easily extendable to the non-Ab elian case [15, 16 ].
Finally we discuss the (1+1)-dimensional case. The Thirring mo del in
(1+1)-dimensions is rewritten into the equivalent scalar eld theory [1, 2]. It
is well known that the (1+1)-dimensional massless Thirring mo del is exactly
solvable in the sense that the mo del is equivalent to the massless free scalar
theory [1]. In this pap er we show, as a sp ecial case of the ab ove formalism,
the massive Thirring model in (1+1)-dimensions is equivalent to the massive
freescalar eld theory in (1+1)-dimensions, up to the next-to-lowest order in
1=m.
In the previous pap er [4] wehave studied the sp ontaneous breakdown of
the chiral symmetry in the massless Thirring mo del, m =0. In this pap er
we consider another extreme limit m !1. According to the universality
hyp othesis, the critical b ehavior of the mo del will b e characterized by a small
numb er of parameters app earing in the original Lagrangian of the mo del such
as symmetry, range of interaction and dimensionality. Therefore, in the large
bare fermion mass limit, the critical b ehavior of the Thirring mo del will b e
characterized by studying the equivalent b osonic theory according to the ab ove
b osonization.
2 Bosonization
1
The Lagrangian of the D -dimensional Thirring mo del (D 2) is given by
G
j j j j j j k k
L = i @ m ( )( ); (1)
Th
2N
j
where is a Dirac spinor and the indices j; k are summed over from 1 to N ,
and the gamma matrices ( =0; :::; D 1) are de ned so as to satisfy the
Cli ord algebra, f ; g =2g 1=2diag (1; 1; :::; 1).
By intro ducing an auxiliary vector eld A , this Lagrangian is equivalently
rewritten as
2
g M
j j j j 2
p
0
L = i (@ i A ) m + A ; (2)
Th
2
N
where wehaveintro duced a parameter M (= 1) with the dimension of mass,
2
g
dim[m]= dim[M ] = 1 and put G = . Thanks to the parameter M , all the
2
M
elds have the corresp onding canonical dimensions: dim[ ]=dim[ ]=(D
1)=2; dim[A ]= (D 2)=2 and then the coupling constant has the dimension:
dim[g ]=(4 D)=2; dim[G]=2 D.
P
N
1 j j
This Lagrangian has O (N ) symmetry.Ifwe adopt the mass term m and put
j
j =1
m = m for j =1; :::; N k and m = m; :::; m for j = N k +1; :::; N , the Lagrangian
j j
has O (N k ) O (k ) symmetry. See the Vafa-Witten argument [17]. 3
The theory with this Lagrangian is identical with that of the massivevector
eld with which the fermion couples minimally, since a kinetic term for A is
generated through the radiative correction although it is absent originally.As
is known from the study of massivevector b oson theory [7], the Thirring mo del
with the Lagrangian (2) is cast into the form whichisinvariant under the
Becchi-Rouet-Stora (BRS) transformation byintro ducing an additional eld
. The eld is called the Stuc kelb erg eld and identi ed with the Batalin-
Fradkin (BF) eld [6] in the general formalism for the constrained system [5].
Then we start from the Lagrangian with covariant gauge- xing [4]:
2
p
g M
j j j j 1 2
00 p
L = i (@ i A ) m + (A NM @ )
Th
2
N
2