1,388 research outputs found
Constrained Superfields and Standard Realization of Nonlinear Supersymmetry
A constrained superfield formalism has been proposed recently to analyze the
low energy physics related to Goldstinos. We prove that this formalism can be
reformulated in the language of standard realization of nonlinear
supersymmetry. New relations have been uncovered in the standard realization of
nonlinear supersymmetry.Comment: 8+1 pages, Latex, expanded discussions on scalar and vector field
Nonlinear Realization of Spontaneously Broken N=1 Supersymmetry Revisited
This paper revisits the nonlinear realization of spontaneously broken N=1
supersymmetry. It is shown that the constrained superfield formalism can be
reinterpreted in the language of standard realization of nonlinear
supersymmetry via a new and simpler route. Explicit formulas of actions are
presented for general renormalizable theories with or without gauge
interactions. The nonlinear Wess-Zumino gauge is discussed and relations are
pointed out for different definitions of gauge fields. In addition, a general
procedure is provided to deal with theories of arbitrary Kahler potentials.Comment: 1+18 pages, LaTe
A Bound on the Superpotential
We prove a general bound on the superpotential in theories with broken
supersymmetry and broken R-symmetry, 2|W|< f_a F, where f_a and F are the
R-axion and Goldstino decay constants, respectively. The bound holds for weakly
coupled as well as strongly coupled theories, thereby providing an exact result
in theories with broken supersymmetry. We briefly discuss several possible
applications.Comment: 20 page
Sigma models with off-shell N=(4,4) supersymmetry and noncommuting complex structures
We describe the conditions for extra supersymmetry in N=(2,2) supersymmetric
nonlinear sigma models written in terms of semichiral superfields. We find that
some of these models have additional off-shell supersymmetry. The (4,4)
supersymmetry introduces geometrical structures on the target-space which are
conveniently described in terms of Yano f-structures and Magri-Morosi
concomitants. On-shell, we relate the new structures to the known
bi-hypercomplex structures.Comment: 20 pages; v2: significant corrections, clarifications, and
reorganization; v3: discussion of supersymmetry vs twisted supersymmetry
added, relevant signs corrected
CP properties of symmetry-constrained two-Higgs-doublet models
The two-Higgs-doublet model can be constrained by imposing Higgs-family
symmetries and/or generalized CP symmetries. It is known that there are only
six independent classes of such symmetry-constrained models. We study the CP
properties of all cases in the bilinear formalism. An exact symmetry implies CP
conservation. We show that soft breaking of the symmetry can lead to
spontaneous CP violation (CPV) in three of the classes.Comment: 14 pages, 2 tables, revised version adapted to the journal
publicatio
Taming the zoo of supersymmetric quantum mechanical models
We show that in many cases nontrivial and complicated supersymmetric quantum
mechanical (SQM) models can be obtained from the simple model describing free
dynamics in flat complex space by two operations: (i) Hamiltonian reduction and
(ii) similarity transformation of the complex supercharges. We conjecture that
it is true for any SQM model.Comment: final version published in JHE
Rigid Supersymmetric Theories in Curved Superspace
We present a uniform treatment of rigid supersymmetric field theories in a
curved spacetime , focusing on four-dimensional theories with four
supercharges. Our discussion is significantly simpler than earlier treatments,
because we use classical background values of the auxiliary fields in the
supergravity multiplet. We demonstrate our procedure using several examples.
For we reproduce the known results in the literature. A
supersymmetric Lagrangian for exists, but unless the
field theory is conformal, it is not reflection positive. We derive the
Lagrangian for and note that the
time direction can be rotated to Euclidean signature and be
compactified to only when the theory has a continuous R-symmetry. The
partition function on is independent of
the parameters of the flat space theory and depends holomorphically on some
complex background gauge fields. We also consider R-invariant
theories on and clarify a few points about them.Comment: 26 pages, uses harvmac; v2 with added reference
Degradation of structure and properties of rail surface layer at long-term operation
The microstructure evolution and properties variation of the surface layer of rail steel after passed 500 and 1000 million tons of gross weight (MTGW) have been investigated. The wear rate increases to 3 and 3.4 times after passed 500 and 1000 MTGW, respectively. The corresponding friction coefficient decreases by 1.4 and 1.1 times. The cementite plates were destroyed and formed the cementite particles of around 10-50 nm in size after passed 500 MTGW. The early stage dynamical recrystallization was observed after passed 1000 MTGW. The mechanisms for these have been suggested. The large number of bend extinction contours is revealed in the surface layer. The internal stress field is evaluated
Bi-harmonic superspace for N=4 d=4 super Yang-Mills
We develop N=4 d=4 bi-harmonic superspace and use it to derive a novel form
for the low-energy effective action in N=4 super Yang-Mills theory. We solve
the N=4 supergauge constraints in this superspace in terms of analytic
superfields. Using these superfields, we construct a simple functional that
respects N=4 supersymmetry and scale invariance. In components, it reproduces
all on-shell terms in the four-derivative part of the N=4 SYM effective action;
in particular, the F^4/X^4 and Wess-Zumino terms. The latter comes out in a
novel SO(3) x SO(3)-invariant form.Comment: 1+19 pages; minor corrections, references adde
Goldstino superfields for spontaneously broken N=2 supersymmetry
We examine spontaneously broken N=2 supersymmetry in four dimensions and
associate a spinor superfield with each Goldstino via a finite supersymmetry
transformation with parameters that are the Grassmann coordinates of N=2
superspace. Making use of a special choice of coset parametrization allows us
to develop a version of nonlinearly realized N=2 supersymmetry for which the
associated Goldstino superfields are defined on harmonic superspace, thereby
providing a natural mechanism for construction of a Goldstino action. The
corresponding superfield Lagrangian is an O(4) multiplet. This property is used
to reformulate the Goldstino action in projective superspace and in
conventional N=2 superspace. We show how to generate matter couplings of the
Goldstinos to supersymmetric matter using the N=2 harmonic, projective and full
superspaces. As a bi-product of our consideration, we also derive an N=2 chiral
Goldstino action.Comment: 20 pages, typos corrected, comments adde
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