6,984 research outputs found
Kondo Effect in Fermi Systems with a Gap: A Renormalization Group Study
We present the results of a Wilson Renormalization Group study of the
single-impurity Kondo and Anderson models in a system with a gap in the
conduction electron spectrum. The behavior of the impurity susceptibility and
the zero-frequency response function, are discussed in the
cases with and without particle-hole symmetry. In addition, for the asymmetric
Anderson model the correlation functions, , are computed.Comment: 10 pages, 10 figure
Firm-Specific Variation and Openness in Emerging Markets
This paper compares the comovement of individual stock returns across emerging markets. Campbell et al. (2001) and Morck et al. (2000) show that the US in the post war period saw rising firm specific stock return variations and thus declining comovement. We detect a similar, albeit weaker, pattern in most, but not all, emerging markets. We further find that higher firm-specific variation is associated with greater capital market openness, but not goods market openness. Moreover, this relationship is magnified by institutional integrity (good government). Goods market openness is associated with higher market-wide variation.http://deepblue.lib.umich.edu/bitstream/2027.42/40009/3/wp623.pd
Federated Hypergradient Descent
In this work, we explore combining automatic hyperparameter tuning and
optimization for federated learning (FL) in an online, one-shot procedure. We
apply a principled approach on a method for adaptive client learning rate,
number of local steps, and batch size. In our federated learning applications,
our primary motivations are minimizing communication budget as well as local
computational resources in the training pipeline. Conventionally,
hyperparameter tuning methods involve at least some degree of trial-and-error,
which is known to be sample inefficient. In order to address our motivations,
we propose FATHOM (Federated AuTomatic Hyperparameter OptiMization) as a
one-shot online procedure. We investigate the challenges and solutions of
deriving analytical gradients with respect to the hyperparameters of interest.
Our approach is inspired by the fact that, with the exception of local data, we
have full knowledge of all components involved in our training process, and
this fact can be exploited in our algorithm impactfully. We show that FATHOM is
more communication efficient than Federated Averaging (FedAvg) with optimized,
static valued hyperparameters, and is also more computationally efficient
overall. As a communication efficient, one-shot online procedure, FATHOM solves
the bottleneck of costly communication and limited local computation, by
eliminating a potentially wasteful tuning process, and by optimizing the
hyperparamters adaptively throughout the training procedure without
trial-and-error. We show our numerical results through extensive empirical
experiments with the Federated EMNIST-62 (FEMNIST) and Federated Stack Overflow
(FSO) datasets, using FedJAX as our baseline framework
Shape of Deconstruction
We construct a six-dimensional Maxwell theory using a latticized extra space,
the continuum limit of which is a shifted torus recently discussed by Dienes.
This toy model exhibits the correspondence between continuum theory and
discrete theory, and give a geometrical insight to theory-space model building.Comment: 10 pages, 2 figures, RevTeX4. a citation adde
Declining Rotation Curve and Brown Dwarf MACHOs
If the Galactic rotation speed at the Solar circle is km s
or smaller, which is supported by several recent studies, the rotation curve of
the Galaxy could be declining in the outermost region. Motivated by this, we
investigate the effect of such declining rotation curve on the estimate of the
MACHO mass and the fractional contribution of the MACHOs to the Galactic dark
halo. Using Hernquist and Plummer halo models instead of the standard halo
model, we find that the MACHO mass could be significantly smaller than that for
the standard halo case. In particular, there exists a certain set of halo
parameters for which the MACHO mass is 0.1 or less and at the same
time the MACHO contribution to the total mass of the halo is almost 100 %. This
result indicates that a halo which consists solely of brown dwarfs can be
consistent with both of the observed microlensing properties and the
constraints from the rotation curve, provided the outer rotation curve is
indeed declining.Comment: 8 pages and 4 figures, accepted for publication in ApJ Letter
The emerging roles and therapeutic potential of cyclin-dependent kinase 11 (CDK11) in human cancer.
Overexpression and/or hyperactivation of cyclin-dependent kinases (CDKs) are common features of most cancer types. CDKs have been shown to play important roles in tumor cell proliferation and growth by controlling cell cycle, transcription, and RNA splicing. CDK4/6 inhibitor palbociclib has been recently approved by the FDA for the treatment of breast cancer. CDK11 is a serine/threonine protein kinase in the CDK family and recent studies have shown that CDK11 also plays critical roles in cancer cell growth and proliferation. A variety of genetic and epigenetic events may cause universal overexpression of CDK11 in human cancers. Inhibition of CDK11 has been shown to lead to cancer cell death and apoptosis. Significant evidence has suggested that CDK11 may be a novel and promising therapeutic target for the treatment of cancers. This review will focus on the emerging roles of CDK11 in human cancers, and provide a proof-of-principle for continued efforts toward targeting CDK11 for effective cancer treatment
Interparticle Potential up to Next-to-leading Order for Gravitational, Electrical, and Dilatonic Forces
Long-range forces up to next-to-leading order are computed in the framework
of the Einstein-Maxwell-dilaton system by means of a semiclassical approach to
gravity. As has been recently shown, this approach is effective if one of the
masses under consideration is significantly greater than all the energies
involved in the system. Further, we obtain the condition for the equilibrium of
charged masses in the system.Comment: 19 pages, 19 figures, RevTeX4.1. Revised version, Title change
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