10,374 research outputs found
Engineering Holographic Superconductor Phase Diagrams
We study how to engineer holographic models with features of a high
temperature superconductor phase diagram. We introduce a field in the bulk
which provides a tunable "doping" parameter in the boundary theory. By
designing how this field changes the effective masses of other order parameter
fields, desired phase diagrams can be engineered. We give examples of
generating phase diagrams with phase boundaries similar to a superconducting
dome and an anti-ferromagnetic phase by including two order parameter fields.
We also explore whether the pseudo gap phase can be described without adding
another order parameter field and discuss the potential scaling symmetry
associated with a quantum critical point hidden under the superconducting dome
in this phase diagram.Comment: 25 pages, 7 figure
Towards Searching for Entangled Photons in the CMB Sky
We explore the possibility of detecting entangled photon pairs from cosmic
microwave background or other cosmological sources coming from two patches of
the sky. The measurements use two detectors with different photon polarizer
directions. When two photon sources are separated by a large angle relative to
the earth, such that each detector has only one photon source in its field of
view, a null test of unentangled photons can be performed. The deviation from
this unentangled background is, in principle, the signature of photon
entanglement. To confirm whether the deviation is consistent with entangled
photons, we derive a photon polarization correlation to compare with, similar
to that in a Bell inequality measurement. However, since photon coincidence
measurement cannot be used to discriminate unentangled cosmic photons, it is
unlikely that the correlation expectation value alone can violate Bell
inequality to provide the signature for entanglement.Comment: 5 pages, 2 figure; references added, typos fixed. v3 revised version
with more discussions on detection possibilities; added references.v4
published version in PR
Concept-wise Fine-tuning Matters in Preventing Negative Transfer
A multitude of prevalent pre-trained models mark a major milestone in the
development of artificial intelligence, while fine-tuning has been a common
practice that enables pretrained models to figure prominently in a wide array
of target datasets. Our empirical results reveal that off-the-shelf finetuning
techniques are far from adequate to mitigate negative transfer caused by two
types of underperforming features in a pre-trained model, including rare
features and spuriously correlated features. Rooted in structural causal models
of predictions after fine-tuning, we propose a Concept-wise fine-tuning
(Concept-Tuning) approach which refines feature representations in the level of
patches with each patch encoding a concept. Concept-Tuning minimizes the
negative impacts of rare features and spuriously correlated features by (1)
maximizing the mutual information between examples in the same category with
regard to a slice of rare features (a patch) and (2) applying front-door
adjustment via attention neural networks in channels and feature slices
(patches). The proposed Concept-Tuning consistently and significantly (by up to
4.76%) improves prior state-of-the-art fine-tuning methods on eleven datasets,
diverse pre-training strategies (supervised and self-supervised ones), various
network architectures, and sample sizes in a target dataset
Geometric Decomposition and Efficient Implementation of High Order Face and Edge Elements
This paper delves into the world of high-order curl and div elements within
finite element methods, providing valuable insights into their geometric
properties, indexing management, and practical implementation considerations.
It first explores the decomposition of Lagrange finite elements. The discussion
then extends to H(div)-conforming finite elements and H(curl)-conforming finite
element spaces by choosing different frames at different sub-simplex. The
required tangential continuity or normal continuity will be imposed by
appropriate choices of the tangential and normal basis. The paper concludes
with a focus on efficient indexing management strategies for degrees of
freedom, offering practical guidance to researchers and engineers. It serves as
a comprehensive resource that bridges the gap between theory and practice in
the realm of high-order curl and div elements in finite element methods, which
are vital for solving vector field problems and understanding electromagnetic
phenomena.Comment: 25 pages, 8 figure
Frustratingly Easy Transferability Estimation
Transferability estimation has been an essential tool in selecting a
pre-trained model and the layers of it to transfer, so as to maximize the
performance on a target task and prevent negative transfer. Existing estimation
algorithms either require intensive training on target tasks or have
difficulties in evaluating the transferability between layers. We propose a
simple, efficient, and effective transferability measure named TransRate. With
single pass through the target data, TransRate measures the transferability as
the mutual information between the features of target examples extracted by a
pre-trained model and labels of them. We overcome the challenge of efficient
mutual information estimation by resorting to coding rate that serves as an
effective alternative to entropy. TransRate is theoretically analyzed to be
closely related to the performance after transfer learning. Despite its
extraordinary simplicity in 10 lines of codes, TransRate performs remarkably
well in extensive evaluations on 22 pre-trained models and 16 downstream tasks
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