• Demetris Christopoulos added an answer:
    Does Heisenberg uncertainty principle apply to Higgs boson or should it be adapted?

    The Higgs boson seems to be a particule difficult to detect (elusive particle), in this context does the uncertainty principle apply as well as it applies to other less elusive particles? More generally, the uncertainty principle gives a lower limit for the product of 2 physical values, but could this limit be more precisely calculated taking into account the fact that the particle interacts more or less easily with other particles?

    Demetris Christopoulos · National and Kapodistrian University of Athens

    I think that we have over-estimate the validity of Fourier Analysis in quantum theories. Fourier is not panacea and the relevant 'Heisenberg uncertainty principle' is not the Holy Grail of Physics.

  • Eugene F Kislyakov added an answer:
    What are the current views and thinking on Physical Reality and Physics?

    It is said that the resolution of the collapse of wave function in a measurement is one of the unsolved problems of quantum mechanics (see "The trouble with physics" by Lee Smolin). There could be, at least, two views on this aspect:

    1. The physical reality presented by QM is somewhat different from that we humans can perceive, however, that is not a serious issue because many things we think should be right are, in fact, not quite right (eg., geocentric picture of solar system). So the QM view is to be accepted.

    2. Any physical theory must be according to the logic and perception of human beings and in that sense some thing is missing within the present QM and so it is not a complete theory. 

    Eugene F Kislyakov · Belarusian State University

    You mean holografic picture, Dmitri?

  • Peter Benjamin added an answer:
    Have eigenmodes of spherical space been compared to CMB map?

    Does anyone know the status of comparison  between eigenmodes of spherical space and CMB map? Is there new result? 

    Peter Benjamin · Harvey Mudd College

    @Victor: Thank you for the citations on a different way to analyse CMB data, that is not in the popular literature. I've scanned them, and realized my post was off topic.  The harmonics I referred to were used to subtract 'vibrations' from the raw data.  To answer your question, perhaps the papers, here up to 2011: http://inspirehep.net/record/920248/references that might interest you, as they do me.

  • Victor Christianto added an answer:
    What is the frequency of acoustic waves in the early universe?

    I just found a paper by Edward Wright (UCLA) on acoustic waves in the early universe. Allow me to ask: a. What is their frequency?, b. is there their imprint in CMb?, c. How can we model them using wave equation?

    Victor Christianto · University of New Mexico

    @Myzafere. Thanks for the link. I will check Cramer's paper. Best wishes

  • Anatoly V Berezkin added an answer:
    How can I introduce an interaction(LJ) between two circular polymer chains?

    I have two circular chains in a spherical confinement.I used this command for interaction between two chains:

    pair_style   lj/cut 1.22

    pair_coeff   1   1   1   1   1.22

    pair_coeff   1   2   1   1   1.22

    pair_coeff   2   2   1   1   1.22

    (two chain=two kind of atom)

    but for some radius of sphere ,two chain disappear or be frozen.

    Anatoly V Berezkin · Technische Universität München

    Dear Zahra! It seems that your system "explodes" or "freezes" due to numerical instability of integrator. Maybe the problem is in your force-field. I recommend carefully read LAMMPS tutorials about pair_style, pair_coeff, and pair_modify commands. In your case probably necessary to type dots explicitly (in FORTRAN it plays a role, maybe for LAMMPS too) like

    pair_coeff 1 1 1.00 1.00 1.22

    Also please check, whether the cut-off is really 1.22. In purely repulsive LJ the value should be 1.12, so maybe you have a misprint. And if you want to have not only cutted, but shifted potential, which attains zero at cut-off distance, you also need the line

    pair_modify shift yes

    This shift (together with cut-off 1.12) provide more smooth behavior of potential around cut-off, and as the result, computations should be more stable. This could solve your problem. You can also try to use shorter time steps (1/10 or 1/100 of desired values) within 1000 or 100000 initial time steps to relax some particle overlaps, producing to high forces and velocities.

  • Shalender Singh added an answer:
    Uncertainty principle
    Is it true in all cases, that the more precise one property is measured the less precise
    the others can be controlled, determined or known?
    Shalender Singh · Indian Institute of Technology Bombay

    Actually uncertainty principle is not about inaccuracy in measurement but it is about representing a system as a probabilistic set of states, where measurements of 2 complimentary observables (not the co-varying observables) do not commute when done is opposite chronology. It  means to say that if first momentum is observed and then position the set of measurements in not the same as if first position is measure and then the momentum. PX is not equal to XP.

    An act of observation realizes one of the states of many states. So the uncertainty is not in the measurement but the underlying nature of the universe. As pointed above, it is actually possible to design experiment in a way that one can measure the most probable state with more accuracy than the h/2PI. It is still the measurement of the most probable state and NOT "THE STATE". If it was just a problem of measurement and not the underlying property of nature, one cannot see quantum tunneling as used in tunneling semi-conductor devices, which uses non-most probable states to operate. 

    I have written some papers on matter light duality, realizing faster than light motion using existing equipment, problem with classical energy at:

    1. https://www.researchgate.net/publication/266143448_Matter-light_duality_and_speed_greater_than_light

    2. https://www.researchgate.net/publication/265643349_Problem_in_the_relativistic_energy_and_momentum_conservation

    3. https://www.researchgate.net/publication/265643274_Extended_principle_of_relativity_beyond_speed_of_light_and_a_method_to_push_particles_beyond_the_speed_of_light

  • Joseph L Alvarez added an answer:
    What is the perfect content and teaching style for an undergraduate physics class?
    I am a physics professor at the University of Leipzig. The semester has just started and I am teaching the experimental physics course for our new undergraduate students. I have done this many times. I thought to place this question will help me to avoid the routine.
    Joseph L Alvarez · Alpha Beta Gamut

    Focus on what you want the students to learn, not on what you are to teach.


    There are wonderful biological questions that illustrate the physics. For example, focusing on what you learned today

    • Why does a giraffe not faint?
    • How much leaf area is required for large tree?
    • Does a cow that grazes on a slope give less milk than one that grazes on flat land.

    Students must supply/estimate information to solve the problem. Answer to within 10%, at minimum set up the problem.

  • Waqas Subhani asked a question:
    What is the concept of Fermi velocity?

    See above.

  • Shalender Singh added an answer:
    whether we store the Light ?
    If we store photons or directly sunlight then we can use it for many purposes like use for lightning at night, to generate electricity at night by using solar cells and the time of availability of light may increased about 24 hours of the day.
    Shalender Singh · Indian Institute of Technology Bombay

    Light is always moving so if you want to store it, it will hit some sort of wall/matter as some time. If the wall is not perfectly reflective it will lead to leak of energy and also absorption/conversion to IR photons. A pre-light condition can be stored like what happens in the battery. 

    I conjecture that light can be stored in the most efficient form if we can create a mechanism to take electrons to a state lower than the ground, which is negative excited state.

  • Shalender Singh added an answer:
    Why light engine technologies for the so-called lightcrafts are not developed quickly enough?
    It is possible to use it in modern cars and starcrafts to travel to nearest stars.
    Shalender Singh · Indian Institute of Technology Bombay

    It is all about kinetic energy imparted to the remaining rocket from loosing fuel. The most optimal kinetic energy is imparted if the fuel leaving the rocket completely converts to photons thus imparting the highest momentum. The big problem with this mechanism is that as the matter completely converts to photons, it is very hard to control the direction of the generated energy. In fact it might need very clever mirroring/lensing to direct the leaving photon away from the desired path of the rocket.

  • Shalender Singh added an answer:
    Do left-hand electromagnetic waves exist in nature? And how can we find it?
    It is well known that there are no natural materials having simultaneously negative values of the dielectric ε and the magnetic μ. In general, we call the materials left-hand Material or double-negative Media. But we have found some special materials in our labs. When the electromagnetic waves go though the left-hand Material by some special frequencies, the waves will be changed from right-hand to left-hand. What I want to ask is that, does a left-hand electromagnetic wave exist in nature? And how can we find it?
    Shalender Singh · Indian Institute of Technology Bombay

    I think what you are asking is whether left hand em wave can exist in vacuum? For left hand EM wave to exist in vacuum the direction of poynting vector should be opposite to the direction of wave, which means it will have negative energy photons. Negative energy photons can be conjectured as photons going into past, which means if you mathematically reverse the source and destination the negative energy will move in past.

    If a inertial reference frame going into past w.r.t. to an observer generates the EM wave it will appear as negative energy photon to the observer. A frame of reference moving with speed greater than light transforms to be as moving into past and thus generates negative energy photons for observer at rest. I have proposed an experiment that can be conducted with existing equipment to generate negative energy EM wave by tunneling electrons above speed of light. Kindly look at this: https://www.researchgate.net/publication/265643274_Extended_principle_of_relativity_beyond_speed_of_light_and_a_method_to_push_particles_beyond_the_speed_of_light

  • Ali Bavali added an answer:
    Can space be disrupted by means of extremely intense laser beams?
    Ali Bavali · Amirkabir University of Technology

    there is an intrinsic non-linearity to the electromagnetic vacuum
    that leads to a field-dependent dielectric tensor:

  • Marc Herzog added an answer:
    How to overlap two laser pulses, (800 and 400 nm) on a sample with an angle of about 45°?

    I have to overlap two laser pulses, one with 800 nm and the other one with 400 nm on a sample. One laser spot is about 20 µm (800 nm) and the other one about 10 µm. The angle between both is about 45°. The laser power of the 800 nm laser pulse is around 20x higher than for the 400 nm laser pulse. A normal ND-Filter didn't worked because than I cannot see the 400 nm anymore.
    Do you have any ideas?


    Marc Herzog · Fritz Haber Institute of the Max Planck Society

    When working with these small spot sizes I suggest to use a compact CCD camara utilizing an objective with sufficiently magnification (e.g. Imaging Source Europe). A pinhole should also work but due to the large angle between the beams the pinhole has to be perfectly located in the surface plane of the sample.

    Two more remarks: When using filters one should check that these do not displace the spots on the sample surface, e.g. by small wedge angles of the filters. In case you want to do pump-probe-type time-resolved experiments you should also be aware that a large angle between pump and probe prevents optimal time-resolution.

  • Ke Lin added an answer:
    What is the significance of the combinational modes in Raman spectra?

    What are the causes for the combinational modes in Raman spectrum?

    Ke Lin · University of Science and Technology of China

    I think the fundamental modes are more important. 

  • Carlos A. Grattoni added an answer:
    The trend of the curve for effective permeability vs saturation and rel. permeability vs saturation remains the same then why don't we use first one?

    Relative permeability importance and physical significance

    Carlos A. Grattoni · University of Leeds

     To use the effective permeability you need to know absolute and porosity.

    The first can be applied to different rocks that belong to the same rock type (even if they absolute permeability is different).

    This difference is similar to: capillary pressure vs. function J of Leverett.

  • Ali Asghar Moshtaghie added an answer:
    Can we use heavy metal concentration ref. values like UCC for sediments of all the regions globally?

    During calculation of Heavy metal contamination levels of  a region through its sediments, can we take base line values like UCC for calculation? If it is so, we may have a chance to miss the assessment of real contamination level of a region. How will you clarify this issue?

    Ali Asghar Moshtaghie · Isfahan University of Medical Sciences

    please make your question more clear.The ref concentration are appeared in most clin chem book

  • Derek Abbott added an answer:
    Do the number of electromagnetic modes in a coax cable depend on its length?
    In a recent paper it has been stated: "It is true that TEM wave modes in a [coax] waveguide do not have a low-frequency cut-off versus the diameter of the [coax] waveguide, but this argument is irrelevant because wave modes do have a cut-off versus the length of the cable. This does not imply that the electrical transport itself has a cut-off; it solely means that, when wave modes are forbidden, electrical transport takes place via non-wave phenomena—such as drift and relaxation—which constitute the form of transport in the quasi-static region of electrodynamics."

    See: http://vixra.org/abs/1403.0964

    This seems to run counter to the mainstream view that electromagnetic wave modes exist even when the wavelength is longer than the cable.

    How can any propagation of electromagnetic radiation occur without waves?

    The question is this: what is the simplest, clearest, and most convincing argument that modes exist independently of length of the coax?

    What is the clearest way to explain it to a skeptic? Any ideas?
    Derek Abbott · University of Adelaide

    Ok, we have now written a paper replying to Laszlo's points:

    In a nutshell, we believe Laszlo has essentially conflated  standing waves with propagating waves.  This is the only way we can see to understand some of his statements.

  • AjayaKumar Kavala added an answer:
    What is the meaning of self consistent? How will it help in poisson, continuity equation?

    See above.

    AjayaKumar Kavala · Indian Institute of Technology Patna

    @Mainak Saka, Thak you

  • Alan Robinson added an answer:
    What is the fundamental difference between modulation instability(MI) and Four Wave Mixing (FWM)?

    The standard text books say that MI and FWM are the different descriptions of the same phenomenon. These say that the MI is the temporal description of the breaking of a CW into pulses. The same thing when viewed in frequency domain manifests itself in the generation of symmetric sidebands around the pump and this is called FWM. But I have doubts regarding that when multiple FWM process is described, why the MI and FWM are treated differently?

    Alan Robinson · 4D Optics

    Kenneth Schepler's reference to Agrawal's book is worth following.

    MI can be explained as a FWM process, but does not require that the input signal is pulsed.  Instability is generally only seen in fibres with anomalous dispersion, where the phase mismatch due to chromatic dispersion is offset by the phase shift induced by self phase modulation (SPM) of the carrier.

    Any amplitude modulation of the signal results in phase modulation via SPM.  Simultaneously, fibre dispersion converts the newly-generated phase modulation to amplitude modulation.  For anomalous dispersion, the converted amplitude modulation reinforces the original perturbation.  The amplitude perturbation is amplified, with peak gain at modulation frequencies such that the rate of generation of phase modulation by SPM and the phase rotation by chromatic dispersion are exactly balanced.  This can be described as phase matched four wave mixing in which the unmodulated optical carrier acts as a degenerate pump, and power is transferred to two equally spaced Stokes and anti-Stokes sidebands.

    For fibres with normal dispersion (negative ps/nm/km), FWM between modulation sidebands and carrier still occurs, but the transfer of energy between carrier and sidebands oscillates along the fibre, with no exponential growth of amplitude modulation.

  • Ankit Verma added an answer:
    What is the relation between FeO and Fe2O3 in steel-making slag?

    Any empirical co-relations or method to link it with any physical measurable quantity will be appreciated.

    Ankit Verma · IIT Kharagpur

    Yes. or some relation using the oxygen potential. The problem is that in literature we have plenty of data using FeO or FeO and FeO1.5 but in industrial data available has Fe total in their analysis. I may looking for something to bridge the gap.

  • Adarsh. M. J. added an answer:
    Does god really exist? Or is it just a product of a weak mind?
    Our universe is entirely self-contained, natural selection is controlling our evolution,so the question is what role is there for "god" to play?
    Adarsh. M. J. · B.V. Bhoomaraddi College of Engineering and Technology (BVBCET)

    People don't believe in GOD because they are good..... they do it thinking... if they believe in GOD.... gods going to make them good.!

  • Doug Dykaar added an answer:
    Is there any Non-linear optical material whose change of refractive index with incident LASER intensity is high?
    For CS2 it is high but we find new material better than it.
    Doug Dykaar · DifTek Lasers, Inc.

    Organics and Lithium Niobate will have low damage thresholds. Also be wary of large refractive index changes that are close absorption edges.

  • Yesid Goyes added an answer:
    Is there any model or equation for ridge dynamics?

    I have a 2D system, you can think of it as a 2D sheet. There is a formation of ridges in this sheet when it is given a constant in-plane pressure. I want to model the ridge dynamics. Is there any model, equation or theory for the ridge formation?

    Yesid Goyes · Industrial University of Santander

    Transport away from mid-ocean ridge by plate motion (Davis and Lister, 1974)

    Davis, E.E., and Lister, C.R.B., 1974, Fundamentals of ridge crest topography. Earth and Planetary Science Letters 21(4): 405-13.

  • Peter Christoph Minkowski added an answer:
    Do you agree with Stephen Hawking's recent conclusion that black holes don't exist?
    Black holes don't exist. I published this many years ago. Cantor's Universe doesn't allow the concept.

    Stephen Hawking now came up with the same conclusion. Read: http://www.spektrum.de/news/es-gibt-keine-schwarzen-loecher/1222059

    In my opinion he is right this time. What is your opinion? Was he right then or is he correct now?
    Peter Christoph Minkowski · Universität Bern

    I suggest that no questions be encapsulate into a weblink , to consult on details attached to the question

  • Marek Wojciech Gutowski added an answer:
    How do you know whether a perfect disc falls heads or tails?

    If you have a perfect disc and flick it like a coin, how do you know which side came up? How can you know that statistically it is perfectly 50/50?

    Marek Wojciech Gutowski · Institute of Physics of the Polish Academy of Sciences

    Steve, you simply don't know before you try infinitely many times.  Even the symmetry argument seems suspected.  Here is why:

    Suppose you order your pupils to draw a square with edges oriented horizontally and vertically and with its vertices marked as "A", "B", "C", and "D", in this very order.  Suppose they only make a vertex "A" visible.  Can you tell what are the marks of other vertices?  "A" is always visible in one of four possible locations, but marking may be clockwise or counterclockwise.  From purely geometrical point of view both orientations are equally good, but I'm pretty sure that they need NOT to be equally likely among those pupils.  Sorry to complicate your thoughts about mixed quantum states even more ...

  • Ali BenMoussa added an answer:
    Is it necessary to plot the Norde function to extract the barrier height and series resistance?

    See above.

    Ali BenMoussa · Solar-Terrestrial Centre of Excellence (STCE)

    For the estimation of the barrier height (at least) you could use optical (photocurrent) or CV methods. 

  • Tomasz Kawalec added an answer:
    Is it possible to observe sustained interference pattern from two independent laser source?


    Tomasz Kawalec · Marian Smoluchowski Institute of Physics, Jagiellonian University

    If you use typical lasers like He-Ne, you need something like 10^-8 s resolution to observe the fringes. If you take two lasers and introduce a relative stabilization by means on an electronic circuit than the fringes are visible for hours (however the lasers are not independent).


  • Shalender Singh added an answer:
    What do you think of the discovery of CERN and INFN about the velocity of neutrinos? It seems that they run faster than light
    Neutrinos run faster than light...
    Shalender Singh · Indian Institute of Technology Bombay

    I do not know validity of CERN experiments but superluminal particles exists very much in everyday life but they come up a particles going into past. So an electron moving faster than light is actually shows up as going into past, which means like a positron.

    The superluminal velocities are real and following paper gives a method to push electrons above the speed of light using existing accelerators and lab equipment: http://www.researchgate.net/publication/265643274_Extended_principle_of_relativity_beyond_speed_of_light_and_a_method_to_push_particles_beyond_the_speed_of_light

    Existence of superluminal velocities and the ability to measure them are two different problems. A frame of reference going above the speed of light will transform into 2 different frames of reference, one going in negative time and other in positive time. For example as I propose in another paper (not yet here), if an electron is pushed above the speed of light it will behave like a positron, which is an electron going into past. Also I propose that all positrons are electrons going above the speed of light, which shows up as going into past. As you can see in this paper, the Doppler Effect of radiation generated from a superluminal frame of reference shows up as negative frequency radiation, which is equivalent to Left hand em wave in vacuum. This radiation finds matter mostly transparent and the only way to detect is the reduction of entropy when it passes through matter.

  • Shalender Singh added an answer:
    Can information travel faster than the speed of light by pushing and pulling something extended between 2 points?
    Let's say an iron rod connects the moon to earth, and a machine connected to one side pulls and pushs it a bit to transmit some message, then a computer connected to the other side read those pushes and pulls. So can we affirm that the information travelled instantaneously between these 2 computers?
    Shalender Singh · Indian Institute of Technology Bombay

    The question is amazing and we cannot simplify or refute it by saying the rod is non-rigid OR the motion moves as molecular motion along the rod. Einstein never took those assumptions of elasticity of the matter OR motion as waves to deduce the special relativity. Let me answer your question as it is:

    Assuming the rod is completely rigid and motion is in-fact matter translation (not wave transmission), still the rod motion will transfer at the speed of light. Why is that? Assume that the 2 different ends of the rod are in the inertial reference frames with 0 relative velocity. For a distance observer also at 0 speed w.r.t. to both, the act of pushing the rod from moon, which implies acceleration will create a space-time voxel around the rod, which will compress the space-time around start of the rod and this voxel will move at the speed of light along the rod (In 4D space-time it is a fixed bundle of trajectories of the space-time bend), expanding when the deceleration is applied to stop the rod. If the rod is accelerated and then just bought to a uniform velocity and never stopped, the rod will appear to be shorter as it shows up in the Lorentz transformation.

    The reason Einstein described gravity and non-uniform motion as bend of space time was exactly because that. The space-time itself bends and warps, which means even the rigid bodies undergo transformation.

    On the other hand superluminal velocities are real and following paper gives a method to push electrons above the speed of light using existing accelerators and lab equipment: http://www.researchgate.net/publication/265643274_Extended_principle_of_relativity_beyond_speed_of_light_and_a_method_to_push_particles_beyond_the_speed_of_light

    Existence of superluminal velocities and the ability to measure them are two different problems. A frame of reference going above the speed of light will transform into 2 different frames of reference, one going in negative time and other in positive time. For example as I propose in another paper (not yet here), if an electron is pushed above the speed of light it will behave like a positron, which is an electron going into past. Also I propose that all positrons are electrons going above the speed of light, which shows up as going into past. As you can see in this paper, the Doppler Effect of radiation generated from a superluminal frame of reference shows up as negative frequency radiation, which is equivalent to Left hand em wave in vacuum. This radiation finds matter mostly transparent and the only way to detect is the reduction of entropy when it passes through matter.

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