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Gauge invariant Lagrangian for
Massive bosonic higher spin field
Hiroyuki Takata
Tomsk state pedagogical university(ТГПУ)
Tomsk, Russia
Hep-th 0707.218
YITP 2007 年8月7日 =Not always totally symmetric, but general tensor.
Based on the work with
I.L. Buchbinder and V.A. Krykhtin
mixed symmetric
Motivations 1
1. Motivated by String/Brane theory.
Point particle sting
World line World sheet
brane
World volume
•Higher dimensional extended object may naturally coupled with various tensor (gauge) field,
those are mixed symmetric in general (ex. )•Various HS states are also in string theory.
•Similarity between Mixed sym. HS alg and Virasoro algNote: we do not restrict ourselves from string/brane theory.
2. We are interested in investigating all irreducible tensor representation under Poincare group in arbitrary dimension.
howeverTotally symmetric tensors do not cover all irreducible representation of Poincare group in case more than 4 space-time dimension.
3. Interacting HS theory is not considered here though, technique introduced here may be useful for that.
Motivations 2, 3
For totally symmetric case, rank of tensor is its spin.For Mixed symmetric case,
a set of number ,(s1 ,s2 ,…) gives correspondent of “spin”. In other word, Young tableaux describe “spin” in this case.
… … … … s1
… … s2
… …
symmetric for ’s and ’s
Each tensor symmetry is described by corresponding young tableaux
…
Introduction
What is spin for mixed symmetric case?
What are conditions for irreducible representation
under Poincare group?
Essence of Mixed symmetiric case is in 2 rows case, so,
Let us consider Massive arbitrary spin field like
, which corresponds Young tableaux with 2 rows (s1 s2)
1. K-G equation,2. Transversality condition3. Traceless condition
4. One more condition for irreducibility under symmetric group of tenser indices
Procedure (plan of talk)
Spin independent formulation introduce c-a op.
Introduce and extending Fock space to formulate HS state with gauge sym.
Treatment of arbitrary spin need more c-a op.
Gauge inv. Formulation need ghosts
Gauge fixing
Irr.eq’s
FROM eq. of irreducibility for tensor field TO Lagrangian.
Constraint eq. With
HS alg.
BRST eq.with
gauge sym.
Lagrangian with
gauge sym.
Idea for introduce gauge sym. : formula
Starting: Irreducibility condition
Symmetric property of (i) symmetric by permutation of 1…s1 and 1…s2
We would like to find a Lagrangian that leads following conditions (i) - ( v) as its equations of motion
Not exist for totally symmetric case
Following 3 conditions are the same as in the totally symmetric case
(iii) Klein-Goldon equation
(iv) Transversality condition
(v) Traceless condition
Auxiliary Fock space representation
•Introduce auxiliary Fock space and creation-annihilation operators and rewrite above constraints.
•Unlike totally symmetric case, K kinds of c-a op. needed for K-row YT. Here we introduce 2 kinds of ones for 2-row YT.
Spin independent formulation introduce c-a op.
Introduce and extending Fock space to formulate HS state with gauge sym.
Treatment of arbitrary spin need more c-a op.
Gauge inv. Formulation need ghosts
Gauge fixing
To rewrite other constraints, define operators
Not exist for totally symmetric
case
Add Helmite conjugate of above operators (for Helmitisity of lagrangian)
(These are not constraints for Ket state but for Bra.)
Higher Spin algebra for Mixed symmetry
Independent generators:
Essential for Irr. HS
Virasoro algebra like
Some sub-algebras
Since these m2, G11, G22 are not regarded as 1st class constraints for neither Ket or Bra, there appear 6 2nd class constraints:
In order to make these right hand sides 1st
class constraints, we can modify algebra and find new representation for that.
Hint: If right hand sides of these commutators have some arbitrary constants, they may control model and make r.h.s constraints. 6 arbitrary parameters will be introduced
Skip this slide
New representation
New representation is sum of original and additional:
we need to introduce 6 creation-annihilation operators corresponding above these 6 second class constraint, namely,
Skip this slide
Spin independent formulation introduce c-a op.
Introduce and extending Fock space to formulate HS state with gauge sym.
Treatment of arbitrary spin need more c-a op.
Gauge inv. Formulation need ghosts
Gauge fixing
To solve problem related spin, add
There are two parameters in above expression, those determine value of spin in our model , by requiring remaining 4 class constraint should be the 1st class.
Skip this slide
It is easily seen that these “new” operators also satisfy the almost the same algebra to the original one
difference: mass m does not cause 2nd class constraint problem and it includes two parameters those make model consistent
Note: modification of inner product is necessary because
…Follow red colors
Skip this slide
From algebra to BRST operator (General procedure)
If constraint operators Ta satisfy closed algebra: [Ta, Tb ] = fab
cTc
Then, BRST operator is defined as
Where a , P b are canonically conjugate ghost variables.
….BRST equation
….Gauge transformation
BRST operator and Fock states
BRST operator is calculated as
, which is nilpotent. Here,
We define extended Fock state, which is independent of ghost momentum for G’s.
-k is ghost number
Spin independent formulation introduce c-a op.
Introduce and extending Fock space to formulate HS state with gauge sym.
Treatment of arbitrary spin need more c-a op.
Gauge inv. Formulation need ghosts
Gauge fixing
BRST equation and Reducible Gauge transformation
We have equation of motion for physical state
Lagrangian from BRST operator
Now, we can construct Lagrangian for fixed spin
K is a operator to define modified inner product.
Gauge fixing (with partial equations of motion)
Gauge fixing conditions to reproduce starting equations
Irreducible mixed spin state under Poincare group
Gauge invariant mixed spin state
BRST
construction
Example the simplest mixed symmetric case: spin (1,1)
State expansion
Lagrangian for spin (1,1) click to simplify
Gauge transformation
where
Tensor and Vector fields
Scalar fields
Reducible Gauge transformation
Gauge transformations of gauge parameters are
where
Return to Lagrangian
Generalization to multi row YT
………
…
… …
……
s2…
s1……
k rows•Irr.condition & algebra, are the same form, but with i=1…k
• k(k+1) 2nd Class constraints.
• k h’s are introduced.
•Gauge fixing cond.
……
•Gauge transformation is reducible,
whose number of stage is k(k+1).
Summary
• Mixed symmetric Irreducible tensor field under Poincare group in arbitrary space-time dimension were studied.
• We found how to construct gauge invariant Lagrangian for the arbitrary mixed symmetric field by using BRST.
• Conversely, gauge fixing condition to reproduce irreducible field was found.
• Spin(1,1) example was explicitly given.
Irr.eq’s
FROM eq. of irreducibility for tensor field TO Lagrangian.
Constraint eq. With
HS alg.
BRST eq.with
gauge sym.
Lagrangian with
gauge sym.
Gauge fixing