## Oct 17, 2016

### Let People Pay

I always believe that people want to do right things and look for right ways to expend their resources — money, time, kindness, attention, or any physical and cognitive assets. So, when it comes to sustainability of economy and society at large, as Amanda Palmer demonstrated it, the question is not “How do we make people pay?” but rather “How do we let people pay?”

Rightness is idiosyncratic originating from ethical, cultural and social principles. In addition, as these factors interact and coevolve with each other, rightness is also dynamic. Even seemingly ubiquitous values like trust could considerably differ across people. So, we may not see the grand general social theory in the near future. Economics I would like to pursue is humbly ad hoc but recognizes such idiosyncrasy, not as fringe, but as fundamental, and designs systems where people feel right and willing to expend their resources. I believe it would be a meaningful progress in social science and, this way, society would be a bit more sustainable and a bit more pleasant.

## Oct 14, 2016

### Matrix Norm

The class (CS532) uses as a textbook Lars Eldén – Matrix Methods in Data Mining and Pattern Recognition. Matrix norm is defined as (p.18) $$\|A\| = \sup_{x\neq0}\frac{\|Ax\|}{\|x\|}$$ I also find an equivalent definition (e.g. p.61) $$\|A\| = \sup_{\|x\|=1}\|Ax\|$$ For a while, I did not get how imposing $\|x\|=1$ is harmless, but now take it as follows. Let $d = \|x\| > 0$ and $y = \frac{x}{\|x\|} = \frac{x}{d}$, and therefore $\|y\|=1$. Then, $$\begin{split} \|A\| &= \sup_{x\neq0}\frac{\|Ax\|}{\|x\|} \\ &= \sup_{x\neq0, \|y\|=1}\frac{\|Ayd\|}{d} \\ &= \sup_{x\neq0, \|y\|=1}\frac{d\|Ay\|}{d} \\ &= \sup_{\|y\|=1}\|Ay\| \end{split}$$

## Jul 24, 2016

Axelrod's chapter (Ch33 Agent-based Modeling as a Bridge Between Disciplines) is a letter to newcomers to ABM, to active modelers, and to William Hamilton. It is very sweet. If a piece like this can be an acceptable academic writing, academia will not be as tasteless as I imagine. Thanks, Robert Axelrod.

## Jun 11, 2016

### Probability and Intuition

I like how they characterize probability theory (emphasis added):
Probability provides a way of summarizing the uncertainty that comes from our laziness and ignorance
—Russell & Norvig (2010, p482)
By laziness, they mean that “It is too much work to list the complete set of antecedents or consequents needed to ensure an exceptionless rule and too hard to use such rules.” I see intuition in a similar way. Especially in some part of academia, where mathematical formalization is pursued, the term tends to be used quite often and loosely. It looks like we implicitly acknowledge our ignorance and the fact that it would be too costly to make every single logic rigorous. Isn't this ironic? I have, in particular, economists in mind, who tend to dismiss narrative approaches in social science. With a bit of introspection, economists should be more humble and try to appreciate “intuitive” science.

## Jan 10, 2016

### Egocentric improvement

Barbara Ehrenreich wrote ‘The Selfish Side of Gratitude’ in The New York Times on December 31, 2015. I found it quite sensible and powerful, especially the last three paragraphs. Here are some of them.
If there is any loving involved in this, it is self-love, and the current hoopla around gratitude is a celebration of onanism.
God is an evasion; there are crowds, whole communities of actual people, many of them with aching backs and tenuous finances, who made the meal possible.
The real challenge of gratitude lies in figuring out how to express our debt to them, whether through generous tips or, say, by supporting their demands for decent pay and better working conditions. But now we’re not talking about gratitude, we’re talking about a far more muscular impulse — and this is, to use the old-fashioned term, “solidarity” — which may involve getting up off the yoga mat.
Self is one of the most difficult aspects to deal with in our life. While it can provide motivations to work hard, stay resilient, and achieve goals, more often we are in trouble handling it. So, we must appreciate such a heads-up. But, at the same time, it may not be so sensible to mock those who need to start somewhere. It is still better to make a start than only to make a New Year’s resolution. We just need to be careful and reflect on why we are doing it every now and then. Being introspective is also on the self-improvement list, isn’t it?