Philosophy paper “Epistemological Explanation of Lean Construction” now published

Cheers!

You might already know that I’m very fond of philosophy. I loved it immediately, as soon as I started my studies in high school in Italy, back in the 90s. I certainly refer to it in my daily life, more or less explicitly; after all, my entire Quantum Prana concept is based on the interaction between Eastern and Western traditions.

Interestingly enough though, sometimes it happens that you don’t see a tangible outcome of your studies for a long period of time. Perhaps, even for over two decades.
And in fact, here it is! A paper entitled “Epistemological Explanation of Lean Construction” that I wrote together with my colleagues at Aalto University, Finland and at the University of Huddersfield, UK.

My contribution consists of a short review and comparison of the classical epistemology of Plato and Aristotle. I then explain how their differences got enhanced through the centuries, until the debate between the Rationalists (René Descartes, Baruch Spinoza, and Gottfried Wilhelm Leibniz) and the British Empiricists (John Locke, George Berkeley, and David Hume), commenting also on their role in cosmology.

I then move forward by shortly analyzing some features of the epistemology of Edmund Husserl and Martin Heidegger, in relation with tacit knowledge and Japanese philosophy.

At this webpage you can read our paper for free or download it in PDF:

https://ascelibrary.org/doi/10.1061/%28ASCE%29CO.1943-7862.0001597

Theoretical physics paper now published

My article on reheating and gravitino production in MSSM inflation is now published in The European Physical Journal C. It is a full access publication, if you are interested you can find it here:

https://link.springer.com/article/10.1140/epjc/s10052-017-5269-8

Abstract

In the framework of MSSM inflation, matter and gravitino production are here investigated through the decay of the fields which are coupled to the udd inflaton, a gauge-invariant combination of squarks. After the end of inflation, the flat direction oscillates about the minimum of its potential, losing at each oscillation about 56% of its energy into bursts of gauge/gaugino and scalar quanta when crossing the origin. These particles then acquire a large inflaton VEV-induced mass and decay perturbatively into the MSSM quanta and gravitinos, transferring the inflaton energy very efficiently via instant preheating. Regarding thermalization, we show that the MSSM degrees of freedom thermalize very quickly, yet not immediately by virtue of the large vacuum expectation value of the inflaton, which breaks the SU(3)C×U(1)YSU(3)C×U(1)Y symmetry into a residual U(1). The energy transfer to the MSSM quanta is very efficient, since full thermalization is achieved after only O(40)O(40) complete oscillations. The udd inflaton thus provides an extremely efficient reheating of the Universe, with a temperature Treh=O(108GeV)Treh=O(108GeV), which allows for instance several mechanisms of baryogenesis. We also compute the gravitino number density from the perturbative decay of the flat direction and of the SUSY multiplet. We find that the gravitinos are produced in negligible amount and satisfy cosmological bounds such as the Big Bang nucleosynthesis (BBN) and dark matter (DM) constraints.

My new article on materials science

Here is my newest paper!

“Thermomechanical generation of fissure patterns on the surface of heated circular wood samples”

https://arxiv.org/abs/1709.03546

We discuss the observation of primary crack patterns on the surface of heated medium density fiberboard (MDF) round samples in inert atmosphere. A constant heat flux irradiates the wood surface, and the primary cracks seem to appear instantaneously at a temperature below the pyrolysis point, \textit{before} any actual charring. Such fissures were originally believed to form mainly by the action of physicochemical processes; on the contrary, we show here that below the pyrolysis temperatures this occurs by means of thermomechanical surface instability. The crack patterns can indeed be explained qualitatively by the simultaneous thermal expansion and softening of the hot surface layer, which is restrained by the colder wood beneath. This generates membrane compressive stresses leading to surface instability. Physically, this is a consequence of the thermomechanical properties of wood, which is a natural thermoplastic. In this paper, the macro-crack topology is reproduced by a full 3D thermomechanical instability model. We obtain the patterns by solving the according eigenvalue problem numerically, by Finite Element Method (FEM). We also formulate the model in 2D, assuming a circular soft thin plate bonded to an elastic foundation, and solve it both analytically and numerically. Finally, we compare our results with analogous crack patterns appearing on the surface of square samples, which we discussed in a previous study. We conclude that very different pattern symmetries (orthotropic, isotropic and circular) might be explained by the same model of thermomechanical surface instability.

First material science paper now published

My paper on thermomechanical processes of charring wood is now published in Combustion And Flame. Here you can download the pdf for free for 50 days, if you are interested 🙂

In our study we develop a model for explaining the crack patterns which are formed on the wood surface when this is exposed to intense heat. It was believed for decades that such cracks are created by physicochemical processes like shrinkage, with impossibility to obtain an analytical model predicting their topology. On the contrary, we show that if one assumes the origin to be thermomechanical, the according analytical model can produce formulas which can describe and predict the crack patterns with an excellent agreement with the observations.

Here is the abstract:


In the assessment of wood charring, it was believed for a long time that physicochemical processes were responsible for the creation of cracking patterns on the charring wood surface. This implied no possibility to rigorously explain the crack topology. In this paper we show instead that below the pyrolysis temperatures, a primary global macro-crack pattern is already completely established by means of a thermomechanical instability phenomenon. First we report experimental observations of the crack patterns on orthotropic (wood) and isotropic (Medium Density Fibreboard) materials in inert atmosphere. Then we solve the 3D thermomechanical buckling problem numerically by using the Finite Element Method, and show that the different crack topologies can be explained qualitatively by the simultaneous thermal expansion and softening, taking into account the directional dependence of the elastic properties. Finally, we formulate a 2D model for a soft layer bonded to an elastic substrate, and find an equation predicting the inter-crack distance in the main crack-pattern for the orthotropic case. We also derive a formula for the critical thermal stress above which the plane surface will wrinkle and buckle. The results can be used for finding new ways to prevent or delay the crack formation, leading to improved fire safety of wood-based products.


I am now working with my colleagues on some developments of the model.

Thermal greetings to everybody!
Andrea /QP

First paper on energy efficiency published

Greetings!

My paper on theoretical modelling of daily hot water consumption in residential buildings is now published in Energy And Buildings. Here follows the abstract:

We consider Domestic Hot Water (DHW) consumption hourly data for Finnish apartments in November and August. Using datasets obtained in a previous work, we formulate a bottom-up model to quantify correlations in the consumption patterns, which are discerned by a different number of occupants for both weekday (WD) and weekend (WE). The analytical formulas thus obtained describe accurately the hourly consumption of any specific dataset. In particular, we can generate the consumption curves for unknown datasets and derive quantitatively the correlations between occupant groups and different seasons. We explain this procedure into details, define the key variables of the model and validate it against the measurements. Our quantitative results are immediately applicable to simulation tools for energy investigations and sizing of heating systems in Finland or areas with similar occupant behavior. More generally, the analytical, inductive method here introduced could be adapted to DHW studies concerning other geographic areas as well. We also argue that this simple, yet effective formalism might also be extended to other engineering contexts that are not strictly related to energy consumption. For example, the main idea could be developed and adapted to those disciplines where understanding dataset correlations constitutes an important investigation tool.


Analytical modelling and prediction formulas for domestic hot water consumption in residential Finnish apartments. Available from: https://www.researchgate.net/publication/309672534_Analytical_modelling_and_prediction_formulas_for_domestic_hot_water_consumption_in_residential_Finnish_apartments.

I will present these results in August, at the 7th International Symposium on Energy in Manchester: http://energy7.nscj.co.uk/

Energetic cheers!
Andrea /QP

 

My new cosmology paper is out!

My latest paper in cosmology is now public! It took many years to write, as it was a single author side-project on a subject that is very different from my main field. My PhD was indeed in particle cosmology, while now I am mostly working on building physics and methods for energy saving in buildings. I am however still relatively active in theoretical physics, and this is meant to be the first article of a comeback into the field.

https://arxiv.org/abs/1702.01051

Here is the abstract:

//

In the framework of MSSM inflation, matter and gravitino production are here investigated through the decay of the fields which are coupled to the udd inflaton, a gauge invariant combination of squarks. After the end of inflation, the flat direction oscillates about the minimum of its potential, losing at each oscillation about 56\% of its energy into bursts of gauge/gaugino and scalar quanta when crossing the origin. These particles then acquire a large inflaton VEV-induced mass and decay perturbatively into the MSSM quanta and gravitinos, transferring the inflaton energy very efficiently via instant preheating.
Regarding thermalization, we show that the MSSM degrees of freedom thermalize very quickly, yet not immediately by virtue of the large vacuum expectation value of the inflaton, which breaks the SU(3)C×U(1)Y symmetry into a residual U(1). Compared to the case of LLe-type inflaton previously studied, we find an even more efficient energy transfer to the MSSM quanta, due to the enhanced particle content of the supersymmetric (SUSY) multiplet that is coupled to the flat direction. Full thermalization is achieved indeed after only O(40) oscillations.
We also compute the gravitino number density from the perturbative decay of the flat direction and of the SUSY multiplet. In agreement with the literature, the inflaton produces a negligible amount of gravitinos and does not raise any cosmological issues. On the contrary, the fields to which it is coupled are responsible for a severe gravitino overproduction problem, which is caused by their large VEV-induced effective masses. We argue that possible solutions might include non-coherent oscillations of multiple flat directions or fragmentation of the inflaton condensate with formation of Q-balls.

//

A lecture on European climate

Here you can find the pdf of my traditional introductory lecture on European weather and climate, for our Master’s level course Building Physics Design I at Aalto University, Espoo (Finland):

European Climate

If you are curious about  weather and climate, and willing to go beyond the stereotypes to see evidence that

– cold weather is not strictly related to latitude

– the Alps are more rainy than Benelux

– Italy can be colder than Finland

take a look at the pdf, which contains a study I did last year. Enjoy 🙂

Primordial Inflation and BICEP2 results

March 17th 2014 has been a historical date for all of us cosmologists: the BICEP2 experiment results seem to provide evidence for  both gravitational waves and the inflationary expansion of the early Universe (even though the observed tensor-to-scalar ratio r = 0.20 at 1σ is in tension with the upper bound r<0.11 at 95% C.L. given by a combination of data from Planck, SPT, ACT and WMAP).

But what is cosmological inflation? As I write extensively in my PhD thesis, it was an accelerated (read: exponential) expansion of the Universe, which occurred right after the Big Bang explosion. It lasted from 10−36 seconds after the Big Bang to sometime between 10−33 and 10−32 seconds (even though r=0.2 now indicates that inflation began even earlier than that).

The theory of inflation was originally proposed in 1980 by Alan Guth and by Katsuhiko Sato, as a mechanism for solving some technical problems of the previous Big Bang theory (the so-called “standard Big Bang scenario”), which didn’t assume an accelerated expansion.

This first version of inflation was anyway predicting a too granular Universe, and still needed adjustments. This problem was solved in 1982 by Andrei Linde, and independently by Andreas Albrecht and Paul Steinhardt, in a revised version
that is now called new inflation. The basic idea is that inflation occurred by a scalar field (i.e. a particle) rolling down a potential energy hill. This particle is called the inflaton: it made the Universe expand fast and then, at the end of inflation, it disappeared decaying into the particle spectrum observed today, namely into the stars, galaxies, dark matter…and us 🙂

Most of my past and present work is devoted to this particle production mechanism indeed. I study how the particle spectrum was generated, according to different theories postulating a specific candidate to become this mysterious “inflaton”.
Professors Andrei Linde and Renata Kallosh get acknowledged of the discovery:


I won’t discuss the theory and the discovery any further, I just paste here links to internet sources which discuss these topics:

Inflation:

My PhD thesis http://arxiv.org/abs/1002.2835

Wikipedia: http://en.wikipedia.org/wiki/Inflation_(cosmology)

The BICEP2 paper: http://arxiv.org/abs/1403.3985

Cosmology discussions:

http://www.scientificamerican.com/article/gravity-waves-cmb-b-mode-polarization/

http://trenchesofdiscovery.blogspot.fi/

http://cosmocoffee.info/

As a last remark, I can say that one thing is certain: after the 2012 detection of the Higgs boson, the 2013 Planck satellite results and this latest discovery of gravitational waves and experimental proof of inflation, we are all definitely living exciting times!

About Quantum Prana, my logo and particle cosmology

My logo certainly carries my initials, however there’s a bit more meaning in it.

As you know from my Home page, I am a theoretical physicist, and I got my PhD at the University of Helsinki in 2010. More specifically, my field was particle cosmology with topic supersymmetric dark matter and supergravity. My papers and theses are found here.

Since I am a certified nerd, it is now clear why I use the name Quantum Prana: quantum physics, though still controversial, provides the basics for most of the physics of the last 100 years. Prana is the Sanskrit word for “life force”, which can be thought as “energy”. Thus Quantum Prana is the quantum energy which “surrounds us and penetrates us; it binds the galaxy together.” (cit.)

This is also the reason why I am called the Dark Matter Guitar 🙂

Related to that, my logo carries the q and p letters in lower case: in mathematics, they are the action-angle coordinates upon which ALL of quantum mechanics (and by extension, quantum field theory) is founded. In fact, by using Hamiltonian mechanics the pair (q,p) describes the quantum states, where q(t) is the position and p(t) is the momentum of the particle.

Starting from q and p, you get all the theory, including cool stuff like the Heisenberg indetermination principle, the Pauli exclusion principle, Schrödinger’s cats and so on.

And on top of that, I also think the symmetry of q p looks cool! 😀