Field-To-Particle Transition and Nonminimal Particles in Sigma Model, Dilaton Gravity and Gauged Supergravity
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25 October 2001 Physics Letters B 519 (2001) 111–120 www.elsevier.com/locate/npe Field-to-particle transition and nonminimal particles in sigma model, dilaton gravity and gauged supergravity Konstantin G. Zloshchastiev Department of Physics, National University of Singapore, Singapore 117542, Republic of Singapore and Department of Theoretical Physics, Dnepropetrovsk State University, Dnepropetrovsk 49050, Ukraine Received 19 July 2001; received in revised form 19 August 2001; accepted 28 August 2001 Editor: T. Yanagida Abstract The field-to-particle transition formalism is applied to the sigma model, and then to the 2D dilaton gravity and gauged supergravity 0-brane solutions. This approach yields the method of the consistent quantization in the vicinity of the nontrivial vacuum induced by a field solution, as well as the recipe of the nontrivial dynamical dimensional reduction which takes into account field fluctuations. It is explicitly shown that in all cases the end product is the so-called nonminimal point particle—an object whose action depends on the world-line curvature. Such objects are suspected to be common at early stages of evolution of the Universe. 2001 Elsevier Science B.V. All rights reserved. PACS: 04.60.Kz; 04.65.+e; 11.25.Sq; 11.27.+d; 12.60.Jv 1. Introduction plain bosonic string in the N-dimensional space–time. The remainder of that section is devoted to quantiza- The studies of the field-to-particle transition grew tion of the obtained effective action as a constrained up from the old program of constructing a theory mechanics with higher derivatives. There we discuss which does not contain matter as an external postu- the recent state of the theory and calculate the quantum lated entity but consider fields as sources of matter corrections to the mass of such a field/string-induced and the particles as special field configurations. How- particle [1]. ever, if one tries to fit a field solution into the particle Further, the 2D gravity [2], which can be viewed interpretation, one encounters eventually the problem also as a dimensional reduction of the 3D BTZ black of how to deal with the field fluctuations. Then it is hole and spherically symmetric solution of 4D dilaton necessary to correctly handle the circumstance that a Einstein–Maxwell gravity, seems to be a good place field solution has an infinite number of degrees of free- for demonstration of the approach on classical and dom, unlike a particle. In Section 2 we demonstrate the quantum level. field-to-particle transition for the soliton-like solutions Finally, in Section 4 we demonstrate how gauged of the N-component 2D sigma model or, equivalently, supergravity 0-brane solutions can be also described in terms of the mechanics of nonminimal particles with rigidity. The latter is invariant under the transforma- E-mail address: [email protected] (K.G. Zloshchastiev). tions of the proper parameter s, so one may recall an- 0370-2693/01/$ – see front matter 2001 Elsevier Science B.V. All rights reserved. PII:S0370-2693(01)01087-5 112 K.G. Zloshchastiev / Physics Letters B 519 (2001) 111–120 other diff-invariant candidates for the role of a 0-brane coinciding with the total energy up to the sign and boundary theory, e.g., the generalized conformal me- Lorentz factor γ (below the boundaries ρi will be chanics of a probe 0-brane [3,4]. However, the probe omitted for brevity). mechanics by construction takes into account neither Let us change to the set of the collective coordinates the field fluctuations near the brane solution nor aris- {σ0 = s,σ1 = ρ} such that ing zero modes, therefore, the nonminimal terms could m = m + m = not arise there in principle. x x (s) e(1)(s)ρ, Xa(x, t) Xa(σ), (2.6) where xm(s) turn out to be the coordinates of a (1+1)- 2. Effective nonminimal-particle action from dimensional point particle, em (s) is the unit spacelike sigma model (1) vector orthogonal to the world-line. Hence, the initial action can be rewritten in new coordinates as In this section, we will construct the nonlinear effective action of the sigma model in the vicinity S[X]= L(X)∆d 2σ, of a localized soliton solution, and then consider its quantum aspects. In fact, here we will describe 1 a b L(X) = σab∂−X ∂+X − U(X), the procedure of the correct transition from field to 2 √ particle degrees of freedom. 1 ∂xm ∂± = ∂ ± ∂ ∆ = = x˙2 ( − where ∆ s ρ , det ∂σk 1 2.1. General formalism ρk), whereas k is the curvature of a particle world-line ε x˙mx¨n = mn Let us begin with the action of the following k √ , (2.7) x˙2 3 N-component 2D sigma model where εmn is the unit antisymmetric tensor. This S[X]= L(X) d2x, (2.1) new action contains the N redundant degrees of freedom which eventually lead to appearance of the where the Lagrangian is given by so-called “zero modes”. To eliminate them we must constrain the model by means of the condition of 1 a ν b L(X) = σab∂ν X ∂ X − U(X), (2.2) vanishing of the functional derivative with respect to 2 field fluctuations about a chosen static solution, and in × where σ is a constant N N matrix, Greek indices run result we will obtain the required effective action. from 0 to 1, and a, b = 1,...,N. The corresponding So, the fluctuations of the fields Xa(σ) in the equations of motion are (s) neighborhood of the static solution Xa (ρ) are given ν b by the expression σab ∂ ∂νX + Ua(X) = 0, (2.3) = ∂U(X) = X (σ) = X(s)(ρ) + δX (σ). (2.8) where we have defined Ua(X) ∂Xa , Uab(X) a a a ∂2 U(X) ∂Xa∂Xb . Suppose, we have the solution which depends Substituting them into the expression (2.7) and con- on the single combination of initial variables, e.g., the (s) sidering the static equations of motion for Xa (ρ) we Lorentz-invariant one: have (below we will omit the superscript “(s)”atX’s (s) = (s) − = − 2 for brevity assuming that all the values are taken on Xa (ρ) Xa γ(x vt) ,γ 1/ 1 v , (2.4) (s) the solutions Xa (ρ)): possessing localized Lagrangian density in the sense that the mass integral over the domain of applicability 2 ∆ a b S[δX]= d σ 2L + σab∂−δX ∂+δX 2 is finite a b a b ρ2 − U δX δX + ∆ σ X δX ab ab µ =− L X(s) dρ < ∞, (2.5) + O δX3 + S,˘ (2.9) ρ1 K.G. Zloshchastiev / Physics Letters B 519 (2001) 111–120 113 where S˘ are surface terms (see below for details), describing the nonminimal point-particle with curva- ture, where µ is the value of the mass integral above, 1 a b L =− σabX X − U, and 2 ρ2 and prime means the derivative with respect to ρ. (0) 1 a b µ α = σabX f dρ = . (2.16) Extremizing this action with respect to δXa one can 2 2 2caˆ obtain the system of equations in partial derivatives for ρ1 field fluctuations: ˘ Let us restore the surface terms S in the action −1 a ac b ∂s ∆ ∂s − ∂ρ ∆∂ρ δX + ∆σ UcbδX (2.15). In general case they are nonzero and give a contribution: a 2 2 + X k x˙ + O δX = 0, (2.10) S =− ds x˙2 µ + α k + α k2 + α k3 , which is the constraint removing redundant degrees eff 1 2 3 of freedom, besides we have denoted the inverse ma- where α =ˇα |ρ2 , αˇ ≡ σ Xa f b,α = α(0) + trix as σ with raised indices. Supposing δXa(s, ρ) = 1 1 ρ1 1 ab 2 2 − ˇ |ρ2 =−1 a b|ρ2 k(s)fa(ρ), in the linear approximations ρk 1 α3 (ρα1) ρ1 ,α3 2 ρσabf f ρ1 .However,the (which naturally guarantees also the smoothness of a natural requirement of vanishing of field fluctuations world-line at ρ → 0, i.e., the absence of a cusp in this at the spatial boundaries leads to the canceling of the point) and O(δX2) = 0 we obtain the system of three terms containing k and k3, as. Thus, below we will ˘ ordinary derivative equations regard the action (2.15), i.e., (2.9) at S = 0, as a basic one. It is straightforward to derive the corresponding 1 d 1 dk √ √ + ck = 0, (2.11) equation of motion in the Frenet basis x˙2 ds x˙2 ds 1 d 1 dk 1 a ac a b a √ √ + − 2 = −f + σ Ucb − cδ f + X = 0, (2.12) c k k 0, (2.17) b x˙2 ds x˙2 ds 2 where c is the constant of separation. Searching for a hence one can see that Eq. (2.11) was nothing but this solution of the last subsystem in the form (we assume equation in the linear approximation with respect to that we can have several c’s and thus no summation curvature, as was expected. over a in this and next formula) Thus, the only problem, which yet demands on resolving is the determination of the concrete (eigen) = + 1 fa ga Xa, (2.13) value of the constant(s) c. It is equivalent to the caˆ eigenvalue problem for the system (2.14) under some we obtain the homogeneous system chosen boundary conditions. If one supposes, for − a + ac − a b = instance, the finiteness of g at infinity then the c’s g σ Ucb caˆ δb g 0.