338,951 research outputs found
Effects of turbulence on laminar separation on aerodynamic surfaces such as airfoils and compressor blading
Activities report include (1) completion of measurements of turbulence amplification in flow about a circular cylinder; (2) initiation of the measurements of turbulence characteristics in flow about a single symmetric airfoil; and, (3) further examination of various matching numerical methods. Emphasis is placed on the experimental program conducted to obtain data on the amplification of the oncoming turbulence and its management
A Deep Architecture for Semantic Matching with Multiple Positional Sentence Representations
Matching natural language sentences is central for many applications such as
information retrieval and question answering. Existing deep models rely on a
single sentence representation or multiple granularity representations for
matching. However, such methods cannot well capture the contextualized local
information in the matching process. To tackle this problem, we present a new
deep architecture to match two sentences with multiple positional sentence
representations. Specifically, each positional sentence representation is a
sentence representation at this position, generated by a bidirectional long
short term memory (Bi-LSTM). The matching score is finally produced by
aggregating interactions between these different positional sentence
representations, through -Max pooling and a multi-layer perceptron. Our
model has several advantages: (1) By using Bi-LSTM, rich context of the whole
sentence is leveraged to capture the contextualized local information in each
positional sentence representation; (2) By matching with multiple positional
sentence representations, it is flexible to aggregate different important
contextualized local information in a sentence to support the matching; (3)
Experiments on different tasks such as question answering and sentence
completion demonstrate the superiority of our model.Comment: Accepted by AAAI-201
On Dimer Models and Closed String Theories
We study some aspects of the recently discovered connection between dimer
models and D-brane gauge theories. We argue that dimer models are also
naturally related to closed string theories on non compact orbifolds of \BC^2
and \BC^3, via their twisted sector R charges, and show that perfect
matchings in dimer models correspond to twisted sector states in the closed
string theory. We also use this formalism to study the combinatorics of some
unstable orbifolds of \BC^2.Comment: 1 + 25 pages, LaTeX, 11 epsf figure
Anomaly-matching and Higgs-less effective theories
We reconsider the low-energy effective theory for Higgs-less electroweak
symmetry breaking: we study the anomaly-matching in the situation where all
Goldstone fields disappear from the spectrum as a result of the Higgs
mechanism. We find that the global SU(2)_L x SU(2)_R x U(1)_{B-L} symmetry of
the underlying theory, which is spontaneously broken to SU(2)_{L+R} x
U(1)_{B-L} has to be anomaly-free. For the sake of generality, we include the
possibility of light spin-1/2 bound states resulting from the dynamics of the
strongly-interacting symmetry-breaking sector, in addition to the Goldstone
bosons. Such composite fermions may have non-standard couplings at the leading
order, and an arbitrary total B-L charge. In order to perform the
anomaly-matching in that case, we generalize the construction of the
Wess-Zumino effective lagrangian. Composite fermions beyond the three known
generations are theoretically allowed, and there are no restrictions from the
anomaly-matching on their couplings nor on their U(1)_{B-L} charge. Absence of
global anomalies for the composite sector as a whole does not preclude
anomalous triple gauge boson couplings arising from composite fermion
triangular diagrams. On the other hand, the trace of B-L over elementary
fermions must vanish if all Goldstone modes are to disappear from the spectrum.Comment: Keywords: Anomalies in Field and String Theories, Spontaneous
Symmetry Breaking, Beyond the Standard Model, Chiral Lagrangians. 33 pages, 7
figure
Comments on the Hierarchy Problem in Effective Theories
We discuss aspects of the hierarchy problem in effective theories with light
scalars and a large, physical ultraviolet (UV) cutoff. We make two main points:
(1) The (naive) fine-tuning observed in an effective theory does not
automatically imply that the UV completion is fine tuned. Instead, it gives a
type of upper bound on the severity of the actual tuning in the UV completion;
the actual tuning can be less severe than the naive tuning or even
non-existent. (2) Within an effective theory, there appear to be two types of
parameter relations that can alleviate the sensitivity of the scalar mass to
the cutoff --- relationships among dimensionless couplings or relationships
among dimensionful parameters. Supersymmetric models provide symmetry-motivated
examples of the former, while scale-invariant models give symmetry-motivated
examples of the latter.Comment: 13 page
National Foreclosure Mitigation Counseling Program Evaluation: Final Report, Rounds 1 and 2
The National Foreclosure Mitigation Counseling (NFMC) program is a special federal appropriation, administered by NeighborWorks (NW) America, to support a rapid expansion of foreclosure intervention counseling in response to the nationwide foreclosure crisis. As this is a federal appropriation, NW America must inform Congress and other entities of the NFMC program's progress. The Urban Institute (UI) was selected by NW America to evaluate the NFMC program. This report presents the final results from UI's evaluation of the first two rounds of the NFMC program (people receiving counseling in 2008 and 2009), including a detailed analysis of program outcomes first described in preliminary reports of November 2009 (Mayer et al.) and December 2010 (Mayer et al.). According to those reports, homeowners receiving NFMC counseling avoided entering foreclosure, successfully cured existing foreclosures, and obtained more favorable loan modifications. This report updates previous analyses and also includes revised models of several homeowner outcomes for NFMC clients counseled in 2008 and 2009. These new models use an improved comparison sample selection design, which addressed potential issues raised by reviewers of earlier analyses, and a better method for controlling for possible selection bias in the NFMC sample. The additional analyses in this report include models of non-modification cures, non-modification redefaults, and foreclosures avoided
Min-Rank Conjecture for Log-Depth Circuits
A completion of an m-by-n matrix A with entries in {0,1,*} is obtained by
setting all *-entries to constants 0 or 1. A system of semi-linear equations
over GF(2) has the form Mx=f(x), where M is a completion of A and f:{0,1}^n -->
{0,1}^m is an operator, the i-th coordinate of which can only depend on
variables corresponding to *-entries in the i-th row of A. We conjecture that
no such system can have more than 2^{n-c\cdot mr(A)} solutions, where c>0 is an
absolute constant and mr(A) is the smallest rank over GF(2) of a completion of
A. The conjecture is related to an old problem of proving super-linear lower
bounds on the size of log-depth boolean circuits computing linear operators x
--> Mx. The conjecture is also a generalization of a classical question about
how much larger can non-linear codes be than linear ones. We prove some special
cases of the conjecture and establish some structural properties of solution
sets.Comment: 22 pages, to appear in: J. Comput.Syst.Sci
- …