1,870 research outputs found
Invertase signal and mature sequence substitutions that delay intercompartmental transport of active enzyme
The role of structural signals in intercompartmental transport has been addressed by the isolation of yeast invertase (SUC2) mutations that cause intracellular accumulation of active enzyme. Two mutations that delay transport of core-glycosylated invertase, but not acid phosphatase, have been mapped in the 5' coding region of SUC2. Both mutations reduce specifically the transport of invertase to a compartment, presumably in the Golgi body, where outer chain carbohydrate is added. Subsequent transport to the cell surface is not similarly delayed. One mutation (SUC2-s1) converts an ala codon to val at position -1 in the signal peptide; the other (SUC2-s2) changes a thr to an ile at position +64 in the mature protein. Mutation s1 results in about a 50-fold reduced rate of invertase transport to the Golgi body which is attributable to defective signal peptide cleavage. While peptide cleavage normally occurs at an ala-ser bond, the s1 mutant form is processed slowly at the adjacent ser-met position giving rise to mature invertase with an N-terminal met residue. s2 mutant invertase is transported about sevenfold more slowly than normal, with no delay in signal peptide cleavage, and no detectable abnormal physical property of the enzyme. This substitution may interfere with the interaction of invertase and a receptor that facilitates transport to the Golgi body
Scaling Functions for Baby Universes in Two-Dimensional Quantum Gravity
We apply the recently proposed transfer matrix formalism to 2-dimensional
quantum gravity coupled to minimal models. We find that the
propagation of a parent universe in geodesic (Euclidean) time is accompanied by
continual emission of baby universes and derive a distribution function
describing their sizes. The limit is generally
thought to correspond to classical geometry, and we indeed find a classical
peak in the universe distribution function. However, we also observe dramatic
quantum effects associated with baby universes at finite length scales.Comment: 20 pages, 6 figures (not included, available upon request), PUPT-142
A Generalized Uncertainty Principle in Quantum Gravity
We discuss a Gedanken experiment for the measurement of the area of the
apparent horizon of a black hole in quantum gravity. Using rather general and
model-independent considerations we find a generalized uncertainty principle
which agrees with a similar result obtained in the framework of string
theories. The result indicates that a minimum length of the order of the Planck
length emerges naturally from any quantum theory of gravity, and that the
concept of black hole is not operationally defined if the mass is smaller than
the Planck mass.Comment: 10 pages, 1 figure (not included), IFUP-TH 3/9
Decay widths in the massive Schwinger model
By a closer inspection of the massive Schwinger model within mass
perturbation theory we find that, in addition to the -boson bound states, a
further type of hybrid bound states has to be included into the model. Further
we explicitly compute the decay widths of the three-boson bound state and of
the lightest hybrid bound state.Comment: 8 pages, Latex file, no figure
A Relation between the Anomalous Dimensions and OPE Coefficients in Asymptotic Free Field Theories
In asymptotic free field theories we show that part of the OPE of the trace
of the stress-energy tensor and an arbitrary composite field is determined by
the anomalous dimension of the composite field. We take examples from the
two-dimensional O(N) non-linear sigma model.Comment: 6 pages, plain TeX, uses harvma
One-loop Effective Lagrangian for a Standard Model with a Heavy Charged Scalar Singlet
We study several problems related to the construction and the use of
effective Lagrangians by considering an extension of the standard model that
includes a heavy scalar singlet coupled to the leptonic doublet. Starting from
the full renormalizable model, we build an effective field theory by
integrating out the heavy scalar. A local effective Lagrangian (up to operators
of dimension six) is obtained by expanding the one-loop effective action in
inverse powers of the heavy mass. This is done by matching some Green functions
calculated with both the full and the effective theories.
Using this simple example we study the renormalization of effective
Lagrangians in general and discuss how they can be used to bound new physics.
We also discuss the effective Lagrangian after spontaneous symmetry breaking,
and the use of the standard model classical equations of motion to rewrite it
in different forms. The final effective Lagrangian in the physical basis is
well suited to the study of the phenomenology of the model, which we comment on
briefly. Finally, as an example of the use of our effective field theory, we
consider the leptonic flavour-changing decay of the boson in the effective
theory and compare the results obtained with the full model calculation.Comment: 39 pages + 7 figures (available upon request), LaTeX, CERN-TH.7030/9
On the connection between Quantum Mechanics and the geometry of two-dimensional strings
On the basis of an area-preserving symmetry in the phase space of a
one-dimensional matrix model - believed to describe two-dimensional string
theory in a black-hole background which also allows for space-time foam - we
give a geometric interpretation of the fact that two-dimensional stringy black
holes are consistent with conventional quantum mechanics due to the infinite
gauged `W-hair' property that characterises them.Comment: 19 page
Is Purity Eternal?
Phenomenological and formal restrictions on the evolution of pure into mixed
states are discussed. In particular, it is argued that, if energy is conserved,
loss of purity is incompatible with the weakest possible form of Lorentz
covariance.Comment: 12 pages, in Plain Tex; section 3 on Lorentz covariance expanded and
improved in response to year-long correspondence with the referee, but the
conclusions are unchanged; UCSBTH-92-2
Screening and confinement in large N_f QCD_2 and in N=1 SYM_2
The screening nature of the potential between external quarks in massless
is derived using an expansion in - the number of
flavors. Applying the same method to the massive model, we find a confining
potential. We consider the N=1 super Yang Mills theory, reveal certain
problematic aspects of its bosonized version and show the associated screening
behavior by applying a point splitting method to the scalar current.Comment: 23 pages, Latex. 1 figur
Screening in Supersymmetric Gauge Theories in Two Dimensions
We show that the string tension in N=1 two-dimensional super Yang-Mills
theory vanishes independently of the representation of the quark anti-quark
external source. We argue that this result persists in SQCD_2 and in
two-dimensional gauge theories with extended supersymmetry or in chiral
invariant models with at least one massless dynamical fermion. We also compute
the string tension for the massive Schwinger model, as a demonstration of the
method of the calculation.Comment: 8 pages, Latex. Minor changes. Accepted to Phys.Lett.
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