64 research outputs found
Four dimensional "old minimal" N=2 supersymmetrization of R^4
We write in superspace the lagrangian containing the fourth power of the Weyl
tensor in the "old minimal" d=4, N=2 supergravity, without local SO(2)
symmetry. Using gauge completion, we analyze the lagrangian in components. We
find out that the auxiliary fields which belong to the Weyl and compensating
vector multiplets have derivative terms and therefore cannot be eliminated
on-shell. Only the auxiliary fields which belong to the compensating nonlinear
multiplet do not get derivatives and could still be eliminated; we check that
this is possible in the leading terms of the lagrangian. We compare this result
to the similar one of "old minimal" N=1 supergravity and we comment on possible
generalizations to other versions of N=1,2 supergravity.Comment: 31 pages, no figures. Minor corrections. Details of the full
calculation included as an appendix. Reference adde
Massive Supergravity and Deconstruction
We present a simple superfield Lagrangian for massive supergravity. It
comprises the minimal supergravity Lagrangian with interactions as well as mass
terms for the metric superfield and the chiral compensator. This is the natural
generalization of the Fierz-Pauli Lagrangian for massive gravity which
comprises mass terms for the metric and its trace. We show that the on-shell
bosonic and fermionic fields are degenerate and have the appropriate spins: 2,
3/2, 3/2 and 1. We then study this interacting Lagrangian using goldstone
superfields. We find that a chiral multiplet of goldstones gets a kinetic term
through mixing, just as the scalar goldstone does in the non-supersymmetric
case. This produces Planck scale (Mpl) interactions with matter and all the
discontinuities and unitarity bounds associated with massive gravity. In
particular, the scale of strong coupling is (Mpl m^4)^1/5, where m is the
multiplet's mass. Next, we consider applications of massive supergravity to
deconstruction. We estimate various quantum effects which generate non-local
operators in theory space. As an example, we show that the single massive
supergravity multiplet in a 2-site model can serve the function of an extra
dimension in anomaly mediation.Comment: 24 pages, 2 figures, some color. Typos fixed and refs added in v
Families of N=2 Strings
In a given 4d spacetime bakcground, one can often construct not one but a
family of distinct N=2 string theories. This is due to the multiple ways N=2
superconformal algebra can be embedded in a given worldsheet theory. We
formulate the principle of obtaining different physical theories by gauging
different embeddings of the same symmetry algebra in the same ``pre-theory.''
We then apply it to N=2 strings and formulate the recipe for finding the
associated parameter spaces of gauging. Flat and curved target spaces of both
(4,0) and (2,2) signatures are considered. We broadly divide the gauging
choices into two classes, denoted by alpha and beta, and show them to be
related by T-duality. The distinction between them is formulated topologically
and hinges on some unique properties of 4d manifolds. We determine what their
parameter spaces of gauging are under certain simplicity ansatz for generic
flat spaces (R^4 and its toroidal compactifications) as well as some curved
spaces. We briefly discuss the spectra of D-branes for both alpha and beta
families.Comment: 66+1 pages, 2 tables, latex 2e, hyperref. ver2: typos corrected,
reference adde
Derivative corrections to the Born-Infeld action through beta-function calculations in N=2 boundary superspace
We calculate the beta-functions for an open string sigma-model in the
presence of a U(1) background. Passing to N=2 boundary superspace, in which the
background is fully characterized by a scalar potential, significantly
facilitates the calculation. Performing the calculation through three loops
yields the equations of motion up to five derivatives on the fieldstrengths,
which upon integration gives the bosonic sector of the effective action for a
single D-brane in trivial bulk background fields through four derivatives and
to all orders in alpha'. Finally, the present calculation shows that demanding
ultra-violet finiteness of the non-linear sigma-model can be reformulated as
the requirement that the background is a deformed stable holomorphic U(1)
bundle.Comment: 25 pages, numerous figure
Note About Classical Dynamics of Pure Spinor String on AdS_5 x S_5 Background
We will discuss some properties of the pure spinor string on the AdS_5 x S_5
background. Using the classical Hamiltonian analysis we will show that the
vertex operator for the massless state that is in the cohomology of the BRST
charges describes on-shell fluctuations around AdS_5 x S_5 background.Comment: 26. pages, added references, v2:corrected typo
Superfield T-duality rules
A geometric treatment of T-duality as an operation which acts on differential
forms in superspace allows us to derive the complete set of T-duality
transformation rules which relate the superfield potentials of D=10 type IIA
supergravity with those of type IIB supergravity including Ramond-Ramond
superfield potentials and fermionic supervielbeins. We show that these rules
are consistent with the superspace supergravity constraints.Comment: 24 pages, latex, no figures. V2 misprints corrected. V3. One
reference ([30]) and a comment on it ('Notice added') on p. 19 adde
Boson-fermion unification, superstrings, and Bohmian mechanics
Bosonic and fermionic particle currents can be introduced in a more unified
way, with the cost of introducing a preferred spacetime foliation. Such a
unified treatment of bosons and fermions naturally emerges from an analogous
superstring current, showing that the preferred spacetime foliation appears
only at the level of effective field theory, not at the fundamental superstring
level. The existence of the preferred spacetime foliation allows an objective
definition of particles associated with quantum field theory in curved
spacetime. Such an objective definition of particles makes the Bohmian
interpretation of particle quantum mechanics more appealing. The superstring
current allows a consistent Bohmian interpretation of superstrings themselves,
including a Bohmian description of string creation and destruction in terms of
string splitting. The Bohmian equations of motion and the corresponding
probabilistic predictions are fully relativistic covariant and do not depend on
the preferred foliation.Comment: 30 pages, 1 figure, revised, to appear in Found. Phy
The ultra-violet question in maximally supersymmetric field theories
We discuss various approaches to the problem of determining which
supersymmetric invariants are permitted as counterterms in maximally
supersymmetric super Yang--Mills and supergravity theories in various
dimensions. We review the superspace non-renormalisation theorems based on
conventional, light-cone, harmonic and certain non-Lorentz covariant
superspaces, and we write down explicitly the relevant invariants. While the
first two types of superspace admit the possibility of one-half BPS
counterterms, of the form and respectively, the last two do not.
This suggests that UV divergences begin with one-quarter BPS counterterms, i.e.
and , and this is supported by an entirely different
approach based on algebraic renormalisation. The algebraic formalism is
discussed for non-renormalisable theories and it is shown how the allowable
supersymmetric counterterms can be determined via cohomological methods. These
results are in agreement with all the explicit computations that have been
carried out to date. In particular, they suggest that maximal supergravity is
likely to diverge at four loops in D=5 and at five loops in D=4, unless other
infinity suppression mechanisms not involving supersymmetry or gauge invariance
are at work.Comment: 56 pages, 1 figure, uses youngtab.sty. Contribution to the
proceedings of the W.E. Heraeus Workhop "Quantum Gravity: Challenges and
Perspectives", Bad Honnef, 14-16 April 2008. References and clarifying
comments adde
Irrational Conformal Field Theory
This is a review of irrational conformal field theory, which includes
rational conformal field theory as a small subspace. Central topics of the
review include the Virasoro master equation, its solutions and the dynamics of
irrational conformal field theory. Discussion of the dynamics includes the
generalized Knizhnik-Zamolodchikov equations on the sphere, the corresponding
heat-like systems on the torus and the generic world- sheet action of
irrational conformal field theory.Comment: 195 pages, Latex, 12 figures, to appear in Physics Reports. Typos
corrected in Sections 13 and 14, and a footnote added in Section 1
Two-Loop O(alpha_s G_F M_Q^2) Heavy-Quark Corrections to the Interactions between Higgs and Intermediate Bosons
By means of a low-energy theorem, we analyze at O(alpha_s G_F M_Q^2) the
shifts in the Standard-Model W^+W^-H and ZZH couplings induced by virtual
high-mass quarks, Q, with M_Q >> M_Z, M_H, which includes the top quark.
Invoking the improved Born approximation, we then find the corresponding
corrections to various four- and five-point Higgs-boson production and decay
processes which involve the W^+W^-H and ZZH vertices with one or both of the
gauge bosons being connected to light-fermion currents, respectively. This
includes e^+e^- -> f anti-f H via Higgs-strahlung, via W^+W^- fusion (with f =
nu_e), and via ZZ fusion (with f = e), as well as H -> 2V -> 4f (with V = W,
Z).Comment: 20 pages (Latex); Physical Review D (to appear
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