477 research outputs found
The Problem of Large-N Phase Transition in Kazakov-Migdal Model of Induced QCD
We study the lattice gauge model proposed recently by Kazakov and Migdal for
inducing QCD. We discuss an extra local Z_N which is a symmetry of the model
and propose of how to construct observables. We discuss the role of the large-N
phase transition which should occur before the one associated with the
continuum limit in order that the model describes continuum QCD. We formulate
the mean field approach to study the large-N phase transition for an arbitrary
potential and show that no first order phase transition occurs for the
quadratic potential.Comment: 10 pages, ITEP-YM-5-9
Descent Relations and Oscillator Level Truncation Method
We reexamine the oscillator level truncation method in the bosonic String
Field Theory (SFT) by calculation the descent relation =Z_3<V_2|. For
the ghost sector we use the fermionic vertices in the standard oscillator
basis. We propose two new schemes for calculations. In the first one we assume
that the insertion satisfies the overlap equation for the vertices and in the
second one we use the direct calculations. In both schemes we get the correct
structures of the exponent and pre-exponent of the vertex <V_2|, but we find
out different normalization factors Z_3.Comment: 21 pages, 10 figures, Late
An Approximate Large Method for Lattice Chiral Models
An approximation is used that permits one to explicitly solve the two-point
Schwinger-Dyson equations of the U(N) lattice chiral models. The approximate
solution correctly predicts a phase transition for dimensions greater than
two. For , the system is in a single disordered phase with a mass
gap. The method reproduces known results well for . For ,
there is a moderate difference with results only in the intermediate
coupling constant region.Comment: Latex file, 19 page
CONTRAST: a discriminative, phylogeny-free approach to multiple informant de novo gene prediction
CONTRAST is a gene predictor that directly incorporates information from multiple alignments and uses discriminative machine learning techniques to give large improvements in prediction over previous methods
Why Pad\'e Approximants reduce the Renormalization-Scale dependence in QFT?
We prove that in the limit where the beta function is dominated by the 1-loop
contribution (``large beta_0 limit'') diagonal Pad\'e Approximants (PA's) of
perturbative series become exactly renormalization scale (RS) independent. This
symmetry suggest that diagonal PA's are resumming correctly contributions from
higher order diagrams that are responsible for the renormalization of the
coupling-constant. Non-diagonal PA's are not exactly invariant, but generally
reduce the RS dependence as compared to partial-sums. In physical cases,
higher-order corrections in the beta function break the symmetry softly,
introducing a small scale and scheme dependence. We also compare the Pad\'e
resummation with the BLM method. We find that in the large-N_f limit using the
BLM scale is identical to resumming the series by a non-diagonal PA.Comment: 25 pages, LateX. Replaced so that the figures would fit into the page
siz
Duality and replicas for a unitary matrix model
In a generalized Airy matrix model, a power replaces the cubic term of
the Airy model introduced by Kontsevich. The parameter corresponds to
Witten's spin index in the theory of intersection numbers of moduli space of
curves. A continuation in down to yields a well studied unitary
matrix model, which exhibits two different phases in the weak and strong
coupling regions, with a third order critical point in-between. The application
of duality and replica to the -th Airy model allows one to recover both the
weak and strong phases of the unitary model, and to establish some new results
for these expansions. Therefore the unitary model is also indirectly a
generating function for intersection numbers.Comment: 18 page, add referece
Witten's Vertex Made Simple
The infinite matrices in Witten's vertex are easy to diagonalize. It just
requires some SL(2,R) lore plus a Watson-Sommerfeld transformation. We
calculate the eigenvalues of all Neumann matrices for all scale dimensions s,
both for matter and ghosts, including fractional s which we use to regulate the
difficult s=0 limit. We find that s=1 eigenfunctions just acquire a p term, and
x gets replaced by the midpoint position.Comment: 24 pages, 2 figures, RevTeX style, typos correcte
Perturbation Theory in Two Dimensional Open String Field Theory
In this paper we develop the covariant string field theory approach to open
2d strings. Upon constructing the vertices, we apply the formalism to calculate
the lowest order contributions to the 4- and 5- point tachyon--tachyon tree
amplitudes. Our results are shown to match the `bulk' amplitude calculations of
Bershadsky and Kutasov. In the present approach the pole structure of the
amplitudes becomes manifest and their origin as coming from the higher string
modes transparent.Comment: 26 page
1+1 dimensional QCD with fundamental bosons and fermions
We analyze the properties of mesons in 1+1 dimensional QCD with bosonic and
fermionic ``quarks'' in the large \nc limit. We study the spectrum in detail
and show that it is impossible to obtain massless mesons including boson
constituents in this model. We quantitatively show how the QCD mass inequality
is realized in two dimensional QCD. We find that the mass inequality is close
to being an equality even when the quarks are light. Methods for obtaining the
properties of ``mesons'' formed from boson and/or fermion constituents are
formulated in an explicit manner convenient for further study. We also analyze
how the physical properties of the mesons such as confinement and asymptotic
freedom are realized.Comment: 20 pages, harvmac, 5 figure
The Pine Needle, May 1947
Libraries and archives collect materials from different cultures and time periods to preserve and make available the historical record. As a result, materials such as those presented here may reflect sexist, misogynistic, abusive, racist, or discriminatory attitudes or actions that some may find disturbing, harmful, or difficult to view.
Both a humor and literary magazine, The Pine Needle was a University of Maine student-produced periodical that began publication in the fall of 1946, the first post-World War II semester that saw GIs returning to campus.
The Needle reflected an edginess and rebellion not found in previous student publications. While past student publications relied on euphemisms for alcohol and dating on campus, The Needle openly promoted the sexualization of co-eds and the use of drugs, tobacco, and alcohol by students who experienced war.
In response to Alumni complaints that The Needle was ...filled with sex and drinking, the University Publications Committee instituted stricter controls. In this issue, the editorial staff announce that starting in Fall 1947, the publication would publish only four issues of the magazine each yearâFall, Christmas, Spring, and Graduation among other changes.
Cover art for this issue is an unsigned ink illustration of chatting university students lined up outside a shop bearing a sign that reads Jifty Cleaners-Dyers. Signs in the shop window reads We Specialize in Grass Stains. 24 Hour Service
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